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imported gcc-4.6.4 source tree from verified upstream tarball.

downloading a git-generated archive based on the 'upstream' tag
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1 files changed, 12782 insertions, 0 deletions

diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
new file mode 100644
index 000000000..8660c755a
--- /dev/null
+++ b/gcc/go/gofrontend/expressions.cc
@@ -0,0 +1,12782 @@
+// expressions.cc -- Go frontend expression handling.
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "go-system.h"
+
+#include <gmp.h>
+
+#ifndef ENABLE_BUILD_WITH_CXX
+extern "C"
+{
+#endif
+
+#include "toplev.h"
+#include "intl.h"
+#include "tree.h"
+#include "gimple.h"
+#include "tree-iterator.h"
+#include "convert.h"
+#include "real.h"
+#include "realmpfr.h"
+
+#ifndef ENABLE_BUILD_WITH_CXX
+}
+#endif
+
+#include "go-c.h"
+#include "gogo.h"
+#include "types.h"
+#include "export.h"
+#include "import.h"
+#include "statements.h"
+#include "lex.h"
+#include "expressions.h"
+
+// Class Expression.
+
+Expression::Expression(Expression_classification classification,
+		       source_location location)
+  : classification_(classification), location_(location)
+{
+}
+
+Expression::~Expression()
+{
+}
+
+// If this expression has a constant integer value, return it.
+
+bool
+Expression::integer_constant_value(bool iota_is_constant, mpz_t val,
+				   Type** ptype) const
+{
+  *ptype = NULL;
+  return this->do_integer_constant_value(iota_is_constant, val, ptype);
+}
+
+// If this expression has a constant floating point value, return it.
+
+bool
+Expression::float_constant_value(mpfr_t val, Type** ptype) const
+{
+  *ptype = NULL;
+  if (this->do_float_constant_value(val, ptype))
+    return true;
+  mpz_t ival;
+  mpz_init(ival);
+  Type* t;
+  bool ret;
+  if (!this->do_integer_constant_value(false, ival, &t))
+    ret = false;
+  else
+    {
+      mpfr_set_z(val, ival, GMP_RNDN);
+      ret = true;
+    }
+  mpz_clear(ival);
+  return ret;
+}
+
+// If this expression has a constant complex value, return it.
+
+bool
+Expression::complex_constant_value(mpfr_t real, mpfr_t imag,
+				   Type** ptype) const
+{
+  *ptype = NULL;
+  if (this->do_complex_constant_value(real, imag, ptype))
+    return true;
+  Type *t;
+  if (this->float_constant_value(real, &t))
+    {
+      mpfr_set_ui(imag, 0, GMP_RNDN);
+      return true;
+    }
+  return false;
+}
+
+// Traverse the expressions.
+
+int
+Expression::traverse(Expression** pexpr, Traverse* traverse)
+{
+  Expression* expr = *pexpr;
+  if ((traverse->traverse_mask() & Traverse::traverse_expressions) != 0)
+    {
+      int t = traverse->expression(pexpr);
+      if (t == TRAVERSE_EXIT)
+	return TRAVERSE_EXIT;
+      else if (t == TRAVERSE_SKIP_COMPONENTS)
+	return TRAVERSE_CONTINUE;
+    }
+  return expr->do_traverse(traverse);
+}
+
+// Traverse subexpressions of this expression.
+
+int
+Expression::traverse_subexpressions(Traverse* traverse)
+{
+  return this->do_traverse(traverse);
+}
+
+// Default implementation for do_traverse for child classes.
+
+int
+Expression::do_traverse(Traverse*)
+{
+  return TRAVERSE_CONTINUE;
+}
+
+// This virtual function is called by the parser if the value of this
+// expression is being discarded.  By default, we warn.  Expressions
+// with side effects override.
+
+void
+Expression::do_discarding_value()
+{
+  this->warn_about_unused_value();
+}
+
+// This virtual function is called to export expressions.  This will
+// only be used by expressions which may be constant.
+
+void
+Expression::do_export(Export*) const
+{
+  gcc_unreachable();
+}
+
+// Warn that the value of the expression is not used.
+
+void
+Expression::warn_about_unused_value()
+{
+  warning_at(this->location(), OPT_Wunused_value, "value computed is not used");
+}
+
+// Note that this expression is an error.  This is called by children
+// when they discover an error.
+
+void
+Expression::set_is_error()
+{
+  this->classification_ = EXPRESSION_ERROR;
+}
+
+// For children to call to report an error conveniently.
+
+void
+Expression::report_error(const char* msg)
+{
+  error_at(this->location_, "%s", msg);
+  this->set_is_error();
+}
+
+// Set types of variables and constants.  This is implemented by the
+// child class.
+
+void
+Expression::determine_type(const Type_context* context)
+{
+  this->do_determine_type(context);
+}
+
+// Set types when there is no context.
+
+void
+Expression::determine_type_no_context()
+{
+  Type_context context;
+  this->do_determine_type(&context);
+}
+
+// Return a tree handling any conversions which must be done during
+// assignment.
+
+tree
+Expression::convert_for_assignment(Translate_context* context, Type* lhs_type,
+				   Type* rhs_type, tree rhs_tree,
+				   source_location location)
+{
+  if (lhs_type == rhs_type)
+    return rhs_tree;
+
+  if (lhs_type->is_error_type() || rhs_type->is_error_type())
+    return error_mark_node;
+
+  if (lhs_type->is_undefined() || rhs_type->is_undefined())
+    {
+      // Make sure we report the error.
+      lhs_type->base();
+      rhs_type->base();
+      return error_mark_node;
+    }
+
+  if (rhs_tree == error_mark_node || TREE_TYPE(rhs_tree) == error_mark_node)
+    return error_mark_node;
+
+  Gogo* gogo = context->gogo();
+
+  tree lhs_type_tree = lhs_type->get_tree(gogo);
+  if (lhs_type_tree == error_mark_node)
+    return error_mark_node;
+
+  if (lhs_type->interface_type() != NULL)
+    {
+      if (rhs_type->interface_type() == NULL)
+	return Expression::convert_type_to_interface(context, lhs_type,
+						     rhs_type, rhs_tree,
+						     location);
+      else
+	return Expression::convert_interface_to_interface(context, lhs_type,
+							  rhs_type, rhs_tree,
+							  false, location);
+    }
+  else if (rhs_type->interface_type() != NULL)
+    return Expression::convert_interface_to_type(context, lhs_type, rhs_type,
+						 rhs_tree, location);
+  else if (lhs_type->is_open_array_type()
+	   && rhs_type->is_nil_type())
+    {
+      // Assigning nil to an open array.
+      gcc_assert(TREE_CODE(lhs_type_tree) == RECORD_TYPE);
+
+      VEC(constructor_elt,gc)* init = VEC_alloc(constructor_elt, gc, 3);
+
+      constructor_elt* elt = VEC_quick_push(constructor_elt, init, NULL);
+      tree field = TYPE_FIELDS(lhs_type_tree);
+      gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)),
+			"__values") == 0);
+      elt->index = field;
+      elt->value = fold_convert(TREE_TYPE(field), null_pointer_node);
+
+      elt = VEC_quick_push(constructor_elt, init, NULL);
+      field = DECL_CHAIN(field);
+      gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)),
+			"__count") == 0);
+      elt->index = field;
+      elt->value = fold_convert(TREE_TYPE(field), integer_zero_node);
+
+      elt = VEC_quick_push(constructor_elt, init, NULL);
+      field = DECL_CHAIN(field);
+      gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)),
+			"__capacity") == 0);
+      elt->index = field;
+      elt->value = fold_convert(TREE_TYPE(field), integer_zero_node);
+
+      tree val = build_constructor(lhs_type_tree, init);
+      TREE_CONSTANT(val) = 1;
+
+      return val;
+    }
+  else if (rhs_type->is_nil_type())
+    {
+      // The left hand side should be a pointer type at the tree
+      // level.
+      gcc_assert(POINTER_TYPE_P(lhs_type_tree));
+      return fold_convert(lhs_type_tree, null_pointer_node);
+    }
+  else if (lhs_type_tree == TREE_TYPE(rhs_tree))
+    {
+      // No conversion is needed.
+      return rhs_tree;
+    }
+  else if (POINTER_TYPE_P(lhs_type_tree)
+	   || INTEGRAL_TYPE_P(lhs_type_tree)
+	   || SCALAR_FLOAT_TYPE_P(lhs_type_tree)
+	   || COMPLEX_FLOAT_TYPE_P(lhs_type_tree))
+    return fold_convert_loc(location, lhs_type_tree, rhs_tree);
+  else if (TREE_CODE(lhs_type_tree) == RECORD_TYPE
+	   && TREE_CODE(TREE_TYPE(rhs_tree)) == RECORD_TYPE)
+    {
+      // This conversion must be permitted by Go, or we wouldn't have
+      // gotten here.
+      gcc_assert(int_size_in_bytes(lhs_type_tree)
+		 == int_size_in_bytes(TREE_TYPE(rhs_tree)));
+      return fold_build1_loc(location, VIEW_CONVERT_EXPR, lhs_type_tree,
+			     rhs_tree);
+    }
+  else
+    {
+      gcc_assert(useless_type_conversion_p(lhs_type_tree, TREE_TYPE(rhs_tree)));
+      return rhs_tree;
+    }
+}
+
+// Return a tree for a conversion from a non-interface type to an
+// interface type.
+
+tree
+Expression::convert_type_to_interface(Translate_context* context,
+				      Type* lhs_type, Type* rhs_type,
+				      tree rhs_tree, source_location location)
+{
+  Gogo* gogo = context->gogo();
+  Interface_type* lhs_interface_type = lhs_type->interface_type();
+  bool lhs_is_empty = lhs_interface_type->is_empty();
+
+  // Since RHS_TYPE is a static type, we can create the interface
+  // method table at compile time.
+
+  // When setting an interface to nil, we just set both fields to
+  // NULL.
+  if (rhs_type->is_nil_type())
+    return lhs_type->get_init_tree(gogo, false);
+
+  // This should have been checked already.
+  gcc_assert(lhs_interface_type->implements_interface(rhs_type, NULL));
+
+  tree lhs_type_tree = lhs_type->get_tree(gogo);
+  if (lhs_type_tree == error_mark_node)
+    return error_mark_node;
+
+  // An interface is a tuple.  If LHS_TYPE is an empty interface type,
+  // then the first field is the type descriptor for RHS_TYPE.
+  // Otherwise it is the interface method table for RHS_TYPE.
+  tree first_field_value;
+  if (lhs_is_empty)
+    first_field_value = rhs_type->type_descriptor_pointer(gogo);
+  else
+    {
+      // Build the interface method table for this interface and this
+      // object type: a list of function pointers for each interface
+      // method.
+      Named_type* rhs_named_type = rhs_type->named_type();
+      bool is_pointer = false;
+      if (rhs_named_type == NULL)
+	{
+	  rhs_named_type = rhs_type->deref()->named_type();
+	  is_pointer = true;
+	}
+      tree method_table;
+      if (rhs_named_type == NULL)
+	method_table = null_pointer_node;
+      else
+	method_table =
+	  rhs_named_type->interface_method_table(gogo, lhs_interface_type,
+						 is_pointer);
+      first_field_value = fold_convert_loc(location, const_ptr_type_node,
+					   method_table);
+    }
+  if (first_field_value == error_mark_node)
+    return error_mark_node;
+
+  // Start building a constructor for the value we will return.
+
+  VEC(constructor_elt,gc)* init = VEC_alloc(constructor_elt, gc, 2);
+
+  constructor_elt* elt = VEC_quick_push(constructor_elt, init, NULL);
+  tree field = TYPE_FIELDS(lhs_type_tree);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)),
+		    (lhs_is_empty ? "__type_descriptor" : "__methods")) == 0);
+  elt->index = field;
+  elt->value = fold_convert_loc(location, TREE_TYPE(field), first_field_value);
+
+  elt = VEC_quick_push(constructor_elt, init, NULL);
+  field = DECL_CHAIN(field);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__object") == 0);
+  elt->index = field;
+
+  if (rhs_type->points_to() != NULL)
+    {
+      //  We are assigning a pointer to the interface; the interface
+      // holds the pointer itself.
+      elt->value = rhs_tree;
+      return build_constructor(lhs_type_tree, init);
+    }
+
+  // We are assigning a non-pointer value to the interface; the
+  // interface gets a copy of the value in the heap.
+
+  tree object_size = TYPE_SIZE_UNIT(TREE_TYPE(rhs_tree));
+
+  tree space = gogo->allocate_memory(rhs_type, object_size, location);
+  space = fold_convert_loc(location, build_pointer_type(TREE_TYPE(rhs_tree)),
+			   space);
+  space = save_expr(space);
+
+  tree ref = build_fold_indirect_ref_loc(location, space);
+  TREE_THIS_NOTRAP(ref) = 1;
+  tree set = fold_build2_loc(location, MODIFY_EXPR, void_type_node,
+			     ref, rhs_tree);
+
+  elt->value = fold_convert_loc(location, TREE_TYPE(field), space);
+
+  return build2(COMPOUND_EXPR, lhs_type_tree, set,
+		build_constructor(lhs_type_tree, init));
+}
+
+// Return a tree for the type descriptor of RHS_TREE, which has
+// interface type RHS_TYPE.  If RHS_TREE is nil the result will be
+// NULL.
+
+tree
+Expression::get_interface_type_descriptor(Translate_context*,
+					  Type* rhs_type, tree rhs_tree,
+					  source_location location)
+{
+  tree rhs_type_tree = TREE_TYPE(rhs_tree);
+  gcc_assert(TREE_CODE(rhs_type_tree) == RECORD_TYPE);
+  tree rhs_field = TYPE_FIELDS(rhs_type_tree);
+  tree v = build3(COMPONENT_REF, TREE_TYPE(rhs_field), rhs_tree, rhs_field,
+		  NULL_TREE);
+  if (rhs_type->interface_type()->is_empty())
+    {
+      gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(rhs_field)),
+			"__type_descriptor") == 0);
+      return v;
+    }
+
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(rhs_field)), "__methods")
+	     == 0);
+  gcc_assert(POINTER_TYPE_P(TREE_TYPE(v)));
+  v = save_expr(v);
+  tree v1 = build_fold_indirect_ref_loc(location, v);
+  gcc_assert(TREE_CODE(TREE_TYPE(v1)) == RECORD_TYPE);
+  tree f = TYPE_FIELDS(TREE_TYPE(v1));
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(f)), "__type_descriptor")
+	     == 0);
+  v1 = build3(COMPONENT_REF, TREE_TYPE(f), v1, f, NULL_TREE);
+
+  tree eq = fold_build2_loc(location, EQ_EXPR, boolean_type_node, v,
+			    fold_convert_loc(location, TREE_TYPE(v),
+					     null_pointer_node));
+  tree n = fold_convert_loc(location, TREE_TYPE(v1), null_pointer_node);
+  return fold_build3_loc(location, COND_EXPR, TREE_TYPE(v1),
+			 eq, n, v1);
+}
+
+// Return a tree for the conversion of an interface type to an
+// interface type.
+
+tree
+Expression::convert_interface_to_interface(Translate_context* context,
+					   Type *lhs_type, Type *rhs_type,
+					   tree rhs_tree, bool for_type_guard,
+					   source_location location)
+{
+  Gogo* gogo = context->gogo();
+  Interface_type* lhs_interface_type = lhs_type->interface_type();
+  bool lhs_is_empty = lhs_interface_type->is_empty();
+
+  tree lhs_type_tree = lhs_type->get_tree(gogo);
+  if (lhs_type_tree == error_mark_node)
+    return error_mark_node;
+
+  // In the general case this requires runtime examination of the type
+  // method table to match it up with the interface methods.
+
+  // FIXME: If all of the methods in the right hand side interface
+  // also appear in the left hand side interface, then we don't need
+  // to do a runtime check, although we still need to build a new
+  // method table.
+
+  // Get the type descriptor for the right hand side.  This will be
+  // NULL for a nil interface.
+
+  if (!DECL_P(rhs_tree))
+    rhs_tree = save_expr(rhs_tree);
+
+  tree rhs_type_descriptor =
+    Expression::get_interface_type_descriptor(context, rhs_type, rhs_tree,
+					      location);
+
+  // The result is going to be a two element constructor.
+
+  VEC(constructor_elt,gc)* init = VEC_alloc(constructor_elt, gc, 2);
+
+  constructor_elt* elt = VEC_quick_push(constructor_elt, init, NULL);
+  tree field = TYPE_FIELDS(lhs_type_tree);
+  elt->index = field;
+
+  if (for_type_guard)
+    {
+      // A type assertion fails when converting a nil interface.
+      tree lhs_type_descriptor = lhs_type->type_descriptor_pointer(gogo);
+      static tree assert_interface_decl;
+      tree call = Gogo::call_builtin(&assert_interface_decl,
+				     location,
+				     "__go_assert_interface",
+				     2,
+				     ptr_type_node,
+				     TREE_TYPE(lhs_type_descriptor),
+				     lhs_type_descriptor,
+				     TREE_TYPE(rhs_type_descriptor),
+				     rhs_type_descriptor);
+      if (call == error_mark_node)
+	return error_mark_node;
+      // This will panic if the interface conversion fails.
+      TREE_NOTHROW(assert_interface_decl) = 0;
+      elt->value = fold_convert_loc(location, TREE_TYPE(field), call);
+    }
+  else if (lhs_is_empty)
+    {
+      // A convertion to an empty interface always succeeds, and the
+      // first field is just the type descriptor of the object.
+      gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)),
+			"__type_descriptor") == 0);
+      gcc_assert(TREE_TYPE(field) == TREE_TYPE(rhs_type_descriptor));
+      elt->value = rhs_type_descriptor;
+    }
+  else
+    {
+      // A conversion to a non-empty interface may fail, but unlike a
+      // type assertion converting nil will always succeed.
+      gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__methods")
+		 == 0);
+      tree lhs_type_descriptor = lhs_type->type_descriptor_pointer(gogo);
+      static tree convert_interface_decl;
+      tree call = Gogo::call_builtin(&convert_interface_decl,
+				     location,
+				     "__go_convert_interface",
+				     2,
+				     ptr_type_node,
+				     TREE_TYPE(lhs_type_descriptor),
+				     lhs_type_descriptor,
+				     TREE_TYPE(rhs_type_descriptor),
+				     rhs_type_descriptor);
+      if (call == error_mark_node)
+	return error_mark_node;
+      // This will panic if the interface conversion fails.
+      TREE_NOTHROW(convert_interface_decl) = 0;
+      elt->value = fold_convert_loc(location, TREE_TYPE(field), call);
+    }
+
+  // The second field is simply the object pointer.
+
+  elt = VEC_quick_push(constructor_elt, init, NULL);
+  field = DECL_CHAIN(field);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__object") == 0);
+  elt->index = field;
+
+  tree rhs_type_tree = TREE_TYPE(rhs_tree);
+  gcc_assert(TREE_CODE(rhs_type_tree) == RECORD_TYPE);
+  tree rhs_field = DECL_CHAIN(TYPE_FIELDS(rhs_type_tree));
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(rhs_field)), "__object") == 0);
+  elt->value = build3(COMPONENT_REF, TREE_TYPE(rhs_field), rhs_tree, rhs_field,
+		      NULL_TREE);
+
+  return build_constructor(lhs_type_tree, init);
+}
+
+// Return a tree for the conversion of an interface type to a
+// non-interface type.
+
+tree
+Expression::convert_interface_to_type(Translate_context* context,
+				      Type *lhs_type, Type* rhs_type,
+				      tree rhs_tree, source_location location)
+{
+  Gogo* gogo = context->gogo();
+  tree rhs_type_tree = TREE_TYPE(rhs_tree);
+
+  tree lhs_type_tree = lhs_type->get_tree(gogo);
+  if (lhs_type_tree == error_mark_node)
+    return error_mark_node;
+
+  // Call a function to check that the type is valid.  The function
+  // will panic with an appropriate runtime type error if the type is
+  // not valid.
+
+  tree lhs_type_descriptor = lhs_type->type_descriptor_pointer(gogo);
+
+  if (!DECL_P(rhs_tree))
+    rhs_tree = save_expr(rhs_tree);
+
+  tree rhs_type_descriptor =
+    Expression::get_interface_type_descriptor(context, rhs_type, rhs_tree,
+					      location);
+
+  tree rhs_inter_descriptor = rhs_type->type_descriptor_pointer(gogo);
+
+  static tree check_interface_type_decl;
+  tree call = Gogo::call_builtin(&check_interface_type_decl,
+				 location,
+				 "__go_check_interface_type",
+				 3,
+				 void_type_node,
+				 TREE_TYPE(lhs_type_descriptor),
+				 lhs_type_descriptor,
+				 TREE_TYPE(rhs_type_descriptor),
+				 rhs_type_descriptor,
+				 TREE_TYPE(rhs_inter_descriptor),
+				 rhs_inter_descriptor);
+  if (call == error_mark_node)
+    return error_mark_node;
+  // This call will panic if the conversion is invalid.
+  TREE_NOTHROW(check_interface_type_decl) = 0;
+
+  // If the call succeeds, pull out the value.
+  gcc_assert(TREE_CODE(rhs_type_tree) == RECORD_TYPE);
+  tree rhs_field = DECL_CHAIN(TYPE_FIELDS(rhs_type_tree));
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(rhs_field)), "__object") == 0);
+  tree val = build3(COMPONENT_REF, TREE_TYPE(rhs_field), rhs_tree, rhs_field,
+		    NULL_TREE);
+
+  // If the value is a pointer, then it is the value we want.
+  // Otherwise it points to the value.
+  if (lhs_type->points_to() == NULL)
+    {
+      val = fold_convert_loc(location, build_pointer_type(lhs_type_tree), val);
+      val = build_fold_indirect_ref_loc(location, val);
+    }
+
+  return build2(COMPOUND_EXPR, lhs_type_tree, call,
+		fold_convert_loc(location, lhs_type_tree, val));
+}
+
+// Convert an expression to a tree.  This is implemented by the child
+// class.  Not that it is not in general safe to call this multiple
+// times for a single expression, but that we don't catch such errors.
+
+tree
+Expression::get_tree(Translate_context* context)
+{
+  // The child may have marked this expression as having an error.
+  if (this->classification_ == EXPRESSION_ERROR)
+    return error_mark_node;
+
+  return this->do_get_tree(context);
+}
+
+// Return a tree for VAL in TYPE.
+
+tree
+Expression::integer_constant_tree(mpz_t val, tree type)
+{
+  if (type == error_mark_node)
+    return error_mark_node;
+  else if (TREE_CODE(type) == INTEGER_TYPE)
+    return double_int_to_tree(type,
+			      mpz_get_double_int(type, val, true));
+  else if (TREE_CODE(type) == REAL_TYPE)
+    {
+      mpfr_t fval;
+      mpfr_init_set_z(fval, val, GMP_RNDN);
+      tree ret = Expression::float_constant_tree(fval, type);
+      mpfr_clear(fval);
+      return ret;
+    }
+  else if (TREE_CODE(type) == COMPLEX_TYPE)
+    {
+      mpfr_t fval;
+      mpfr_init_set_z(fval, val, GMP_RNDN);
+      tree real = Expression::float_constant_tree(fval, TREE_TYPE(type));
+      mpfr_clear(fval);
+      tree imag = build_real_from_int_cst(TREE_TYPE(type),
+					  integer_zero_node);
+      return build_complex(type, real, imag);
+    }
+  else
+    gcc_unreachable();
+}
+
+// Return a tree for VAL in TYPE.
+
+tree
+Expression::float_constant_tree(mpfr_t val, tree type)
+{
+  if (type == error_mark_node)
+    return error_mark_node;
+  else if (TREE_CODE(type) == INTEGER_TYPE)
+    {
+      mpz_t ival;
+      mpz_init(ival);
+      mpfr_get_z(ival, val, GMP_RNDN);
+      tree ret = Expression::integer_constant_tree(ival, type);
+      mpz_clear(ival);
+      return ret;
+    }
+  else if (TREE_CODE(type) == REAL_TYPE)
+    {
+      REAL_VALUE_TYPE r1;
+      real_from_mpfr(&r1, val, type, GMP_RNDN);
+      REAL_VALUE_TYPE r2;
+      real_convert(&r2, TYPE_MODE(type), &r1);
+      return build_real(type, r2);
+    }
+  else if (TREE_CODE(type) == COMPLEX_TYPE)
+    {
+      REAL_VALUE_TYPE r1;
+      real_from_mpfr(&r1, val, TREE_TYPE(type), GMP_RNDN);
+      REAL_VALUE_TYPE r2;
+      real_convert(&r2, TYPE_MODE(TREE_TYPE(type)), &r1);
+      tree imag = build_real_from_int_cst(TREE_TYPE(type),
+					  integer_zero_node);
+      return build_complex(type, build_real(TREE_TYPE(type), r2), imag);
+    }
+  else
+    gcc_unreachable();
+}
+
+// Return a tree for REAL/IMAG in TYPE.
+
+tree
+Expression::complex_constant_tree(mpfr_t real, mpfr_t imag, tree type)
+{
+  if (type == error_mark_node)
+    return error_mark_node;
+  else if (TREE_CODE(type) == INTEGER_TYPE || TREE_CODE(type) == REAL_TYPE)
+    return Expression::float_constant_tree(real, type);
+  else if (TREE_CODE(type) == COMPLEX_TYPE)
+    {
+      REAL_VALUE_TYPE r1;
+      real_from_mpfr(&r1, real, TREE_TYPE(type), GMP_RNDN);
+      REAL_VALUE_TYPE r2;
+      real_convert(&r2, TYPE_MODE(TREE_TYPE(type)), &r1);
+
+      REAL_VALUE_TYPE r3;
+      real_from_mpfr(&r3, imag, TREE_TYPE(type), GMP_RNDN);
+      REAL_VALUE_TYPE r4;
+      real_convert(&r4, TYPE_MODE(TREE_TYPE(type)), &r3);
+
+      return build_complex(type, build_real(TREE_TYPE(type), r2),
+			   build_real(TREE_TYPE(type), r4));
+    }
+  else
+    gcc_unreachable();
+}
+
+// Return a tree which evaluates to true if VAL, of arbitrary integer
+// type, is negative or is more than the maximum value of BOUND_TYPE.
+// If SOFAR is not NULL, it is or'red into the result.  The return
+// value may be NULL if SOFAR is NULL.
+
+tree
+Expression::check_bounds(tree val, tree bound_type, tree sofar,
+			 source_location loc)
+{
+  tree val_type = TREE_TYPE(val);
+  tree ret = NULL_TREE;
+
+  if (!TYPE_UNSIGNED(val_type))
+    {
+      ret = fold_build2_loc(loc, LT_EXPR, boolean_type_node, val,
+			    build_int_cst(val_type, 0));
+      if (ret == boolean_false_node)
+	ret = NULL_TREE;
+    }
+
+  if ((TYPE_UNSIGNED(val_type) && !TYPE_UNSIGNED(bound_type))
+      || TYPE_SIZE(val_type) > TYPE_SIZE(bound_type))
+    {
+      tree max = TYPE_MAX_VALUE(bound_type);
+      tree big = fold_build2_loc(loc, GT_EXPR, boolean_type_node, val,
+				 fold_convert_loc(loc, val_type, max));
+      if (big == boolean_false_node)
+	;
+      else if (ret == NULL_TREE)
+	ret = big;
+      else
+	ret = fold_build2_loc(loc, TRUTH_OR_EXPR, boolean_type_node,
+			      ret, big);
+    }
+
+  if (ret == NULL_TREE)
+    return sofar;
+  else if (sofar == NULL_TREE)
+    return ret;
+  else
+    return fold_build2_loc(loc, TRUTH_OR_EXPR, boolean_type_node,
+			   sofar, ret);
+}
+
+// Error expressions.  This are used to avoid cascading errors.
+
+class Error_expression : public Expression
+{
+ public:
+  Error_expression(source_location location)
+    : Expression(EXPRESSION_ERROR, location)
+  { }
+
+ protected:
+  bool
+  do_is_constant() const
+  { return true; }
+
+  bool
+  do_integer_constant_value(bool, mpz_t val, Type**) const
+  {
+    mpz_set_ui(val, 0);
+    return true;
+  }
+
+  bool
+  do_float_constant_value(mpfr_t val, Type**) const
+  {
+    mpfr_set_ui(val, 0, GMP_RNDN);
+    return true;
+  }
+
+  bool
+  do_complex_constant_value(mpfr_t real, mpfr_t imag, Type**) const
+  {
+    mpfr_set_ui(real, 0, GMP_RNDN);
+    mpfr_set_ui(imag, 0, GMP_RNDN);
+    return true;
+  }
+
+  void
+  do_discarding_value()
+  { }
+
+  Type*
+  do_type()
+  { return Type::make_error_type(); }
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  Expression*
+  do_copy()
+  { return this; }
+
+  bool
+  do_is_addressable() const
+  { return true; }
+
+  tree
+  do_get_tree(Translate_context*)
+  { return error_mark_node; }
+};
+
+Expression*
+Expression::make_error(source_location location)
+{
+  return new Error_expression(location);
+}
+
+// An expression which is really a type.  This is used during parsing.
+// It is an error if these survive after lowering.
+
+class
+Type_expression : public Expression
+{
+ public:
+  Type_expression(Type* type, source_location location)
+    : Expression(EXPRESSION_TYPE, location),
+      type_(type)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse)
+  { return Type::traverse(this->type_, traverse); }
+
+  Type*
+  do_type()
+  { return this->type_; }
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  void
+  do_check_types(Gogo*)
+  { this->report_error(_("invalid use of type")); }
+
+  Expression*
+  do_copy()
+  { return this; }
+
+  tree
+  do_get_tree(Translate_context*)
+  { gcc_unreachable(); }
+
+ private:
+  // The type which we are representing as an expression.
+  Type* type_;
+};
+
+Expression*
+Expression::make_type(Type* type, source_location location)
+{
+  return new Type_expression(type, location);
+}
+
+// Class Parser_expression.
+
+Type*
+Parser_expression::do_type()
+{
+  // We should never really ask for the type of a Parser_expression.
+  // However, it can happen, at least when we have an invalid const
+  // whose initializer refers to the const itself.  In that case we
+  // may ask for the type when lowering the const itself.
+  gcc_assert(saw_errors());
+  return Type::make_error_type();
+}
+
+// Class Var_expression.
+
+// Lower a variable expression.  Here we just make sure that the
+// initialization expression of the variable has been lowered.  This
+// ensures that we will be able to determine the type of the variable
+// if necessary.
+
+Expression*
+Var_expression::do_lower(Gogo* gogo, Named_object* function, int)
+{
+  if (this->variable_->is_variable())
+    {
+      Variable* var = this->variable_->var_value();
+      // This is either a local variable or a global variable.  A
+      // reference to a variable which is local to an enclosing
+      // function will be a reference to a field in a closure.
+      if (var->is_global())
+	function = NULL;
+      var->lower_init_expression(gogo, function);
+    }
+  return this;
+}
+
+// Return the type of a reference to a variable.
+
+Type*
+Var_expression::do_type()
+{
+  if (this->variable_->is_variable())
+    return this->variable_->var_value()->type();
+  else if (this->variable_->is_result_variable())
+    return this->variable_->result_var_value()->type();
+  else
+    gcc_unreachable();
+}
+
+// Determine the type of a reference to a variable.
+
+void
+Var_expression::do_determine_type(const Type_context*)
+{
+  if (this->variable_->is_variable())
+    this->variable_->var_value()->determine_type();
+}
+
+// Something takes the address of this variable.  This means that we
+// may want to move the variable onto the heap.
+
+void
+Var_expression::do_address_taken(bool escapes)
+{
+  if (!escapes)
+    ;
+  else if (this->variable_->is_variable())
+    this->variable_->var_value()->set_address_taken();
+  else if (this->variable_->is_result_variable())
+    this->variable_->result_var_value()->set_address_taken();
+  else
+    gcc_unreachable();
+}
+
+// Get the tree for a reference to a variable.
+
+tree
+Var_expression::do_get_tree(Translate_context* context)
+{
+  return this->variable_->get_tree(context->gogo(), context->function());
+}
+
+// Make a reference to a variable in an expression.
+
+Expression*
+Expression::make_var_reference(Named_object* var, source_location location)
+{
+  if (var->is_sink())
+    return Expression::make_sink(location);
+
+  // FIXME: Creating a new object for each reference to a variable is
+  // wasteful.
+  return new Var_expression(var, location);
+}
+
+// Class Temporary_reference_expression.
+
+// The type.
+
+Type*
+Temporary_reference_expression::do_type()
+{
+  return this->statement_->type();
+}
+
+// Called if something takes the address of this temporary variable.
+// We never have to move temporary variables to the heap, but we do
+// need to know that they must live in the stack rather than in a
+// register.
+
+void
+Temporary_reference_expression::do_address_taken(bool)
+{
+  this->statement_->set_is_address_taken();
+}
+
+// Get a tree referring to the variable.
+
+tree
+Temporary_reference_expression::do_get_tree(Translate_context*)
+{
+  return this->statement_->get_decl();
+}
+
+// Make a reference to a temporary variable.
+
+Expression*
+Expression::make_temporary_reference(Temporary_statement* statement,
+				     source_location location)
+{
+  return new Temporary_reference_expression(statement, location);
+}
+
+// A sink expression--a use of the blank identifier _.
+
+class Sink_expression : public Expression
+{
+ public:
+  Sink_expression(source_location location)
+    : Expression(EXPRESSION_SINK, location),
+      type_(NULL), var_(NULL_TREE)
+  { }
+
+ protected:
+  void
+  do_discarding_value()
+  { }
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  Expression*
+  do_copy()
+  { return new Sink_expression(this->location()); }
+
+  tree
+  do_get_tree(Translate_context*);
+
+ private:
+  // The type of this sink variable.
+  Type* type_;
+  // The temporary variable we generate.
+  tree var_;
+};
+
+// Return the type of a sink expression.
+
+Type*
+Sink_expression::do_type()
+{
+  if (this->type_ == NULL)
+    return Type::make_sink_type();
+  return this->type_;
+}
+
+// Determine the type of a sink expression.
+
+void
+Sink_expression::do_determine_type(const Type_context* context)
+{
+  if (context->type != NULL)
+    this->type_ = context->type;
+}
+
+// Return a temporary variable for a sink expression.  This will
+// presumably be a write-only variable which the middle-end will drop.
+
+tree
+Sink_expression::do_get_tree(Translate_context* context)
+{
+  if (this->var_ == NULL_TREE)
+    {
+      gcc_assert(this->type_ != NULL && !this->type_->is_sink_type());
+      this->var_ = create_tmp_var(this->type_->get_tree(context->gogo()),
+				  "blank");
+    }
+  return this->var_;
+}
+
+// Make a sink expression.
+
+Expression*
+Expression::make_sink(source_location location)
+{
+  return new Sink_expression(location);
+}
+
+// Class Func_expression.
+
+// FIXME: Can a function expression appear in a constant expression?
+// The value is unchanging.  Initializing a constant to the address of
+// a function seems like it could work, though there might be little
+// point to it.
+
+// Traversal.
+
+int
+Func_expression::do_traverse(Traverse* traverse)
+{
+  return (this->closure_ == NULL
+	  ? TRAVERSE_CONTINUE
+	  : Expression::traverse(&this->closure_, traverse));
+}
+
+// Return the type of a function expression.
+
+Type*
+Func_expression::do_type()
+{
+  if (this->function_->is_function())
+    return this->function_->func_value()->type();
+  else if (this->function_->is_function_declaration())
+    return this->function_->func_declaration_value()->type();
+  else
+    gcc_unreachable();
+}
+
+// Get the tree for a function expression without evaluating the
+// closure.
+
+tree
+Func_expression::get_tree_without_closure(Gogo* gogo)
+{
+  Function_type* fntype;
+  if (this->function_->is_function())
+    fntype = this->function_->func_value()->type();
+  else if (this->function_->is_function_declaration())
+    fntype = this->function_->func_declaration_value()->type();
+  else
+    gcc_unreachable();
+
+  // Builtin functions are handled specially by Call_expression.  We
+  // can't take their address.
+  if (fntype->is_builtin())
+    {
+      error_at(this->location(), "invalid use of special builtin function %qs",
+	       this->function_->name().c_str());
+      return error_mark_node;
+    }
+
+  Named_object* no = this->function_;
+
+  tree id = no->get_id(gogo);
+  if (id == error_mark_node)
+    return error_mark_node;
+
+  tree fndecl;
+  if (no->is_function())
+    fndecl = no->func_value()->get_or_make_decl(gogo, no, id);
+  else if (no->is_function_declaration())
+    fndecl = no->func_declaration_value()->get_or_make_decl(gogo, no, id);
+  else
+    gcc_unreachable();
+
+  if (fndecl == error_mark_node)
+    return error_mark_node;
+
+  return build_fold_addr_expr_loc(this->location(), fndecl);
+}
+
+// Get the tree for a function expression.  This is used when we take
+// the address of a function rather than simply calling it.  If the
+// function has a closure, we must use a trampoline.
+
+tree
+Func_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+
+  tree fnaddr = this->get_tree_without_closure(gogo);
+  if (fnaddr == error_mark_node)
+    return error_mark_node;
+
+  gcc_assert(TREE_CODE(fnaddr) == ADDR_EXPR
+	     && TREE_CODE(TREE_OPERAND(fnaddr, 0)) == FUNCTION_DECL);
+  TREE_ADDRESSABLE(TREE_OPERAND(fnaddr, 0)) = 1;
+
+  // For a normal non-nested function call, that is all we have to do.
+  if (!this->function_->is_function()
+      || this->function_->func_value()->enclosing() == NULL)
+    {
+      gcc_assert(this->closure_ == NULL);
+      return fnaddr;
+    }
+
+  // For a nested function call, we have to always allocate a
+  // trampoline.  If we don't always allocate, then closures will not
+  // be reliably distinct.
+  Expression* closure = this->closure_;
+  tree closure_tree;
+  if (closure == NULL)
+    closure_tree = null_pointer_node;
+  else
+    {
+      // Get the value of the closure.  This will be a pointer to
+      // space allocated on the heap.
+      closure_tree = closure->get_tree(context);
+      if (closure_tree == error_mark_node)
+	return error_mark_node;
+      gcc_assert(POINTER_TYPE_P(TREE_TYPE(closure_tree)));
+    }
+
+  // Now we need to build some code on the heap.  This code will load
+  // the static chain pointer with the closure and then jump to the
+  // body of the function.  The normal gcc approach is to build the
+  // code on the stack.  Unfortunately we can not do that, as Go
+  // permits us to return the function pointer.
+
+  return gogo->make_trampoline(fnaddr, closure_tree, this->location());
+}
+
+// Make a reference to a function in an expression.
+
+Expression*
+Expression::make_func_reference(Named_object* function, Expression* closure,
+				source_location location)
+{
+  return new Func_expression(function, closure, location);
+}
+
+// Class Unknown_expression.
+
+// Return the name of an unknown expression.
+
+const std::string&
+Unknown_expression::name() const
+{
+  return this->named_object_->name();
+}
+
+// Lower a reference to an unknown name.
+
+Expression*
+Unknown_expression::do_lower(Gogo*, Named_object*, int)
+{
+  source_location location = this->location();
+  Named_object* no = this->named_object_;
+  Named_object* real;
+  if (!no->is_unknown())
+    real = no;
+  else
+    {
+      real = no->unknown_value()->real_named_object();
+      if (real == NULL)
+	{
+	  if (this->is_composite_literal_key_)
+	    return this;
+	  error_at(location, "reference to undefined name %qs",
+		   this->named_object_->message_name().c_str());
+	  return Expression::make_error(location);
+	}
+    }
+  switch (real->classification())
+    {
+    case Named_object::NAMED_OBJECT_CONST:
+      return Expression::make_const_reference(real, location);
+    case Named_object::NAMED_OBJECT_TYPE:
+      return Expression::make_type(real->type_value(), location);
+    case Named_object::NAMED_OBJECT_TYPE_DECLARATION:
+      if (this->is_composite_literal_key_)
+	return this;
+      error_at(location, "reference to undefined type %qs",
+	       real->message_name().c_str());
+      return Expression::make_error(location);
+    case Named_object::NAMED_OBJECT_VAR:
+      return Expression::make_var_reference(real, location);
+    case Named_object::NAMED_OBJECT_FUNC:
+    case Named_object::NAMED_OBJECT_FUNC_DECLARATION:
+      return Expression::make_func_reference(real, NULL, location);
+    case Named_object::NAMED_OBJECT_PACKAGE:
+      if (this->is_composite_literal_key_)
+	return this;
+      error_at(location, "unexpected reference to package");
+      return Expression::make_error(location);
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Make a reference to an unknown name.
+
+Expression*
+Expression::make_unknown_reference(Named_object* no, source_location location)
+{
+  gcc_assert(no->resolve()->is_unknown());
+  return new Unknown_expression(no, location);
+}
+
+// A boolean expression.
+
+class Boolean_expression : public Expression
+{
+ public:
+  Boolean_expression(bool val, source_location location)
+    : Expression(EXPRESSION_BOOLEAN, location),
+      val_(val), type_(NULL)
+  { }
+
+  static Expression*
+  do_import(Import*);
+
+ protected:
+  bool
+  do_is_constant() const
+  { return true; }
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  Expression*
+  do_copy()
+  { return this; }
+
+  tree
+  do_get_tree(Translate_context*)
+  { return this->val_ ? boolean_true_node : boolean_false_node; }
+
+  void
+  do_export(Export* exp) const
+  { exp->write_c_string(this->val_ ? "true" : "false"); }
+
+ private:
+  // The constant.
+  bool val_;
+  // The type as determined by context.
+  Type* type_;
+};
+
+// Get the type.
+
+Type*
+Boolean_expression::do_type()
+{
+  if (this->type_ == NULL)
+    this->type_ = Type::make_boolean_type();
+  return this->type_;
+}
+
+// Set the type from the context.
+
+void
+Boolean_expression::do_determine_type(const Type_context* context)
+{
+  if (this->type_ != NULL && !this->type_->is_abstract())
+    ;
+  else if (context->type != NULL && context->type->is_boolean_type())
+    this->type_ = context->type;
+  else if (!context->may_be_abstract)
+    this->type_ = Type::lookup_bool_type();
+}
+
+// Import a boolean constant.
+
+Expression*
+Boolean_expression::do_import(Import* imp)
+{
+  if (imp->peek_char() == 't')
+    {
+      imp->require_c_string("true");
+      return Expression::make_boolean(true, imp->location());
+    }
+  else
+    {
+      imp->require_c_string("false");
+      return Expression::make_boolean(false, imp->location());
+    }
+}
+
+// Make a boolean expression.
+
+Expression*
+Expression::make_boolean(bool val, source_location location)
+{
+  return new Boolean_expression(val, location);
+}
+
+// Class String_expression.
+
+// Get the type.
+
+Type*
+String_expression::do_type()
+{
+  if (this->type_ == NULL)
+    this->type_ = Type::make_string_type();
+  return this->type_;
+}
+
+// Set the type from the context.
+
+void
+String_expression::do_determine_type(const Type_context* context)
+{
+  if (this->type_ != NULL && !this->type_->is_abstract())
+    ;
+  else if (context->type != NULL && context->type->is_string_type())
+    this->type_ = context->type;
+  else if (!context->may_be_abstract)
+    this->type_ = Type::lookup_string_type();
+}
+
+// Build a string constant.
+
+tree
+String_expression::do_get_tree(Translate_context* context)
+{
+  return context->gogo()->go_string_constant_tree(this->val_);
+}
+
+// Export a string expression.
+
+void
+String_expression::do_export(Export* exp) const
+{
+  std::string s;
+  s.reserve(this->val_.length() * 4 + 2);
+  s += '"';
+  for (std::string::const_iterator p = this->val_.begin();
+       p != this->val_.end();
+       ++p)
+    {
+      if (*p == '\\' || *p == '"')
+	{
+	  s += '\\';
+	  s += *p;
+	}
+      else if (*p >= 0x20 && *p < 0x7f)
+	s += *p;
+      else if (*p == '\n')
+	s += "\\n";
+      else if (*p == '\t')
+	s += "\\t";
+      else
+	{
+	  s += "\\x";
+	  unsigned char c = *p;
+	  unsigned int dig = c >> 4;
+	  s += dig < 10 ? '0' + dig : 'A' + dig - 10;
+	  dig = c & 0xf;
+	  s += dig < 10 ? '0' + dig : 'A' + dig - 10;
+	}
+    }
+  s += '"';
+  exp->write_string(s);
+}
+
+// Import a string expression.
+
+Expression*
+String_expression::do_import(Import* imp)
+{
+  imp->require_c_string("\"");
+  std::string val;
+  while (true)
+    {
+      int c = imp->get_char();
+      if (c == '"' || c == -1)
+	break;
+      if (c != '\\')
+	val += static_cast<char>(c);
+      else
+	{
+	  c = imp->get_char();
+	  if (c == '\\' || c == '"')
+	    val += static_cast<char>(c);
+	  else if (c == 'n')
+	    val += '\n';
+	  else if (c == 't')
+	    val += '\t';
+	  else if (c == 'x')
+	    {
+	      c = imp->get_char();
+	      unsigned int vh = c >= '0' && c <= '9' ? c - '0' : c - 'A' + 10;
+	      c = imp->get_char();
+	      unsigned int vl = c >= '0' && c <= '9' ? c - '0' : c - 'A' + 10;
+	      char v = (vh << 4) | vl;
+	      val += v;
+	    }
+	  else
+	    {
+	      error_at(imp->location(), "bad string constant");
+	      return Expression::make_error(imp->location());
+	    }
+	}
+    }
+  return Expression::make_string(val, imp->location());
+}
+
+// Make a string expression.
+
+Expression*
+Expression::make_string(const std::string& val, source_location location)
+{
+  return new String_expression(val, location);
+}
+
+// Make an integer expression.
+
+class Integer_expression : public Expression
+{
+ public:
+  Integer_expression(const mpz_t* val, Type* type, source_location location)
+    : Expression(EXPRESSION_INTEGER, location),
+      type_(type)
+  { mpz_init_set(this->val_, *val); }
+
+  static Expression*
+  do_import(Import*);
+
+  // Return whether VAL fits in the type.
+  static bool
+  check_constant(mpz_t val, Type*, source_location);
+
+  // Write VAL to export data.
+  static void
+  export_integer(Export* exp, const mpz_t val);
+
+ protected:
+  bool
+  do_is_constant() const
+  { return true; }
+
+  bool
+  do_integer_constant_value(bool, mpz_t val, Type** ptype) const;
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context* context);
+
+  void
+  do_check_types(Gogo*);
+
+  tree
+  do_get_tree(Translate_context*);
+
+  Expression*
+  do_copy()
+  { return Expression::make_integer(&this->val_, this->type_,
+				    this->location()); }
+
+  void
+  do_export(Export*) const;
+
+ private:
+  // The integer value.
+  mpz_t val_;
+  // The type so far.
+  Type* type_;
+};
+
+// Return an integer constant value.
+
+bool
+Integer_expression::do_integer_constant_value(bool, mpz_t val,
+					      Type** ptype) const
+{
+  if (this->type_ != NULL)
+    *ptype = this->type_;
+  mpz_set(val, this->val_);
+  return true;
+}
+
+// Return the current type.  If we haven't set the type yet, we return
+// an abstract integer type.
+
+Type*
+Integer_expression::do_type()
+{
+  if (this->type_ == NULL)
+    this->type_ = Type::make_abstract_integer_type();
+  return this->type_;
+}
+
+// Set the type of the integer value.  Here we may switch from an
+// abstract type to a real type.
+
+void
+Integer_expression::do_determine_type(const Type_context* context)
+{
+  if (this->type_ != NULL && !this->type_->is_abstract())
+    ;
+  else if (context->type != NULL
+	   && (context->type->integer_type() != NULL
+	       || context->type->float_type() != NULL
+	       || context->type->complex_type() != NULL))
+    this->type_ = context->type;
+  else if (!context->may_be_abstract)
+    this->type_ = Type::lookup_integer_type("int");
+}
+
+// Return true if the integer VAL fits in the range of the type TYPE.
+// Otherwise give an error and return false.  TYPE may be NULL.
+
+bool
+Integer_expression::check_constant(mpz_t val, Type* type,
+				   source_location location)
+{
+  if (type == NULL)
+    return true;
+  Integer_type* itype = type->integer_type();
+  if (itype == NULL || itype->is_abstract())
+    return true;
+
+  int bits = mpz_sizeinbase(val, 2);
+
+  if (itype->is_unsigned())
+    {
+      // For an unsigned type we can only accept a nonnegative number,
+      // and we must be able to represent at least BITS.
+      if (mpz_sgn(val) >= 0
+	  && bits <= itype->bits())
+	return true;
+    }
+  else
+    {
+      // For a signed type we need an extra bit to indicate the sign.
+      // We have to handle the most negative integer specially.
+      if (bits + 1 <= itype->bits()
+	  || (bits <= itype->bits()
+	      && mpz_sgn(val) < 0
+	      && (mpz_scan1(val, 0)
+		  == static_cast<unsigned long>(itype->bits() - 1))
+	      && mpz_scan0(val, itype->bits()) == ULONG_MAX))
+	return true;
+    }
+
+  error_at(location, "integer constant overflow");
+  return false;
+}
+
+// Check the type of an integer constant.
+
+void
+Integer_expression::do_check_types(Gogo*)
+{
+  if (this->type_ == NULL)
+    return;
+  if (!Integer_expression::check_constant(this->val_, this->type_,
+					  this->location()))
+    this->set_is_error();
+}
+
+// Get a tree for an integer constant.
+
+tree
+Integer_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  tree type;
+  if (this->type_ != NULL && !this->type_->is_abstract())
+    type = this->type_->get_tree(gogo);
+  else if (this->type_ != NULL && this->type_->float_type() != NULL)
+    {
+      // We are converting to an abstract floating point type.
+      type = Type::lookup_float_type("float64")->get_tree(gogo);
+    }
+  else if (this->type_ != NULL && this->type_->complex_type() != NULL)
+    {
+      // We are converting to an abstract complex type.
+      type = Type::lookup_complex_type("complex128")->get_tree(gogo);
+    }
+  else
+    {
+      // If we still have an abstract type here, then this is being
+      // used in a constant expression which didn't get reduced for
+      // some reason.  Use a type which will fit the value.  We use <,
+      // not <=, because we need an extra bit for the sign bit.
+      int bits = mpz_sizeinbase(this->val_, 2);
+      if (bits < INT_TYPE_SIZE)
+	type = Type::lookup_integer_type("int")->get_tree(gogo);
+      else if (bits < 64)
+	type = Type::lookup_integer_type("int64")->get_tree(gogo);
+      else
+	type = long_long_integer_type_node;
+    }
+  return Expression::integer_constant_tree(this->val_, type);
+}
+
+// Write VAL to export data.
+
+void
+Integer_expression::export_integer(Export* exp, const mpz_t val)
+{
+  char* s = mpz_get_str(NULL, 10, val);
+  exp->write_c_string(s);
+  free(s);
+}
+
+// Export an integer in a constant expression.
+
+void
+Integer_expression::do_export(Export* exp) const
+{
+  Integer_expression::export_integer(exp, this->val_);
+  // A trailing space lets us reliably identify the end of the number.
+  exp->write_c_string(" ");
+}
+
+// Import an integer, floating point, or complex value.  This handles
+// all these types because they all start with digits.
+
+Expression*
+Integer_expression::do_import(Import* imp)
+{
+  std::string num = imp->read_identifier();
+  imp->require_c_string(" ");
+  if (!num.empty() && num[num.length() - 1] == 'i')
+    {
+      mpfr_t real;
+      size_t plus_pos = num.find('+', 1);
+      size_t minus_pos = num.find('-', 1);
+      size_t pos;
+      if (plus_pos == std::string::npos)
+	pos = minus_pos;
+      else if (minus_pos == std::string::npos)
+	pos = plus_pos;
+      else
+	{
+	  error_at(imp->location(), "bad number in import data: %qs",
+		   num.c_str());
+	  return Expression::make_error(imp->location());
+	}
+      if (pos == std::string::npos)
+	mpfr_set_ui(real, 0, GMP_RNDN);
+      else
+	{
+	  std::string real_str = num.substr(0, pos);
+	  if (mpfr_init_set_str(real, real_str.c_str(), 10, GMP_RNDN) != 0)
+	    {
+	      error_at(imp->location(), "bad number in import data: %qs",
+		       real_str.c_str());
+	      return Expression::make_error(imp->location());
+	    }
+	}
+
+      std::string imag_str;
+      if (pos == std::string::npos)
+	imag_str = num;
+      else
+	imag_str = num.substr(pos);
+      imag_str = imag_str.substr(0, imag_str.size() - 1);
+      mpfr_t imag;
+      if (mpfr_init_set_str(imag, imag_str.c_str(), 10, GMP_RNDN) != 0)
+	{
+	  error_at(imp->location(), "bad number in import data: %qs",
+		   imag_str.c_str());
+	  return Expression::make_error(imp->location());
+	}
+      Expression* ret = Expression::make_complex(&real, &imag, NULL,
+						 imp->location());
+      mpfr_clear(real);
+      mpfr_clear(imag);
+      return ret;
+    }
+  else if (num.find('.') == std::string::npos
+	   && num.find('E') == std::string::npos)
+    {
+      mpz_t val;
+      if (mpz_init_set_str(val, num.c_str(), 10) != 0)
+	{
+	  error_at(imp->location(), "bad number in import data: %qs",
+		   num.c_str());
+	  return Expression::make_error(imp->location());
+	}
+      Expression* ret = Expression::make_integer(&val, NULL, imp->location());
+      mpz_clear(val);
+      return ret;
+    }
+  else
+    {
+      mpfr_t val;
+      if (mpfr_init_set_str(val, num.c_str(), 10, GMP_RNDN) != 0)
+	{
+	  error_at(imp->location(), "bad number in import data: %qs",
+		   num.c_str());
+	  return Expression::make_error(imp->location());
+	}
+      Expression* ret = Expression::make_float(&val, NULL, imp->location());
+      mpfr_clear(val);
+      return ret;
+    }
+}
+
+// Build a new integer value.
+
+Expression*
+Expression::make_integer(const mpz_t* val, Type* type,
+			 source_location location)
+{
+  return new Integer_expression(val, type, location);
+}
+
+// Floats.
+
+class Float_expression : public Expression
+{
+ public:
+  Float_expression(const mpfr_t* val, Type* type, source_location location)
+    : Expression(EXPRESSION_FLOAT, location),
+      type_(type)
+  {
+    mpfr_init_set(this->val_, *val, GMP_RNDN);
+  }
+
+  // Constrain VAL to fit into TYPE.
+  static void
+  constrain_float(mpfr_t val, Type* type);
+
+  // Return whether VAL fits in the type.
+  static bool
+  check_constant(mpfr_t val, Type*, source_location);
+
+  // Write VAL to export data.
+  static void
+  export_float(Export* exp, const mpfr_t val);
+
+ protected:
+  bool
+  do_is_constant() const
+  { return true; }
+
+  bool
+  do_float_constant_value(mpfr_t val, Type**) const;
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  { return Expression::make_float(&this->val_, this->type_,
+				  this->location()); }
+
+  tree
+  do_get_tree(Translate_context*);
+
+  void
+  do_export(Export*) const;
+
+ private:
+  // The floating point value.
+  mpfr_t val_;
+  // The type so far.
+  Type* type_;
+};
+
+// Constrain VAL to fit into TYPE.
+
+void
+Float_expression::constrain_float(mpfr_t val, Type* type)
+{
+  Float_type* ftype = type->float_type();
+  if (ftype != NULL && !ftype->is_abstract())
+    {
+      tree type_tree = ftype->type_tree();
+      REAL_VALUE_TYPE rvt;
+      real_from_mpfr(&rvt, val, type_tree, GMP_RNDN);
+      real_convert(&rvt, TYPE_MODE(type_tree), &rvt);
+      mpfr_from_real(val, &rvt, GMP_RNDN);
+    }
+}
+
+// Return a floating point constant value.
+
+bool
+Float_expression::do_float_constant_value(mpfr_t val, Type** ptype) const
+{
+  if (this->type_ != NULL)
+    *ptype = this->type_;
+  mpfr_set(val, this->val_, GMP_RNDN);
+  return true;
+}
+
+// Return the current type.  If we haven't set the type yet, we return
+// an abstract float type.
+
+Type*
+Float_expression::do_type()
+{
+  if (this->type_ == NULL)
+    this->type_ = Type::make_abstract_float_type();
+  return this->type_;
+}
+
+// Set the type of the float value.  Here we may switch from an
+// abstract type to a real type.
+
+void
+Float_expression::do_determine_type(const Type_context* context)
+{
+  if (this->type_ != NULL && !this->type_->is_abstract())
+    ;
+  else if (context->type != NULL
+	   && (context->type->integer_type() != NULL
+	       || context->type->float_type() != NULL
+	       || context->type->complex_type() != NULL))
+    this->type_ = context->type;
+  else if (!context->may_be_abstract)
+    this->type_ = Type::lookup_float_type("float64");
+}
+
+// Return true if the floating point value VAL fits in the range of
+// the type TYPE.  Otherwise give an error and return false.  TYPE may
+// be NULL.
+
+bool
+Float_expression::check_constant(mpfr_t val, Type* type,
+				 source_location location)
+{
+  if (type == NULL)
+    return true;
+  Float_type* ftype = type->float_type();
+  if (ftype == NULL || ftype->is_abstract())
+    return true;
+
+  // A NaN or Infinity always fits in the range of the type.
+  if (mpfr_nan_p(val) || mpfr_inf_p(val) || mpfr_zero_p(val))
+    return true;
+
+  mp_exp_t exp = mpfr_get_exp(val);
+  mp_exp_t max_exp;
+  switch (ftype->bits())
+    {
+    case 32:
+      max_exp = 128;
+      break;
+    case 64:
+      max_exp = 1024;
+      break;
+    default:
+      gcc_unreachable();
+    }
+  if (exp > max_exp)
+    {
+      error_at(location, "floating point constant overflow");
+      return false;
+    }
+  return true;
+}
+
+// Check the type of a float value.
+
+void
+Float_expression::do_check_types(Gogo*)
+{
+  if (this->type_ == NULL)
+    return;
+
+  if (!Float_expression::check_constant(this->val_, this->type_,
+					this->location()))
+    this->set_is_error();
+
+  Integer_type* integer_type = this->type_->integer_type();
+  if (integer_type != NULL)
+    {
+      if (!mpfr_integer_p(this->val_))
+	this->report_error(_("floating point constant truncated to integer"));
+      else
+	{
+	  gcc_assert(!integer_type->is_abstract());
+	  mpz_t ival;
+	  mpz_init(ival);
+	  mpfr_get_z(ival, this->val_, GMP_RNDN);
+	  Integer_expression::check_constant(ival, integer_type,
+					     this->location());
+	  mpz_clear(ival);
+	}
+    }
+}
+
+// Get a tree for a float constant.
+
+tree
+Float_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  tree type;
+  if (this->type_ != NULL && !this->type_->is_abstract())
+    type = this->type_->get_tree(gogo);
+  else if (this->type_ != NULL && this->type_->integer_type() != NULL)
+    {
+      // We have an abstract integer type.  We just hope for the best.
+      type = Type::lookup_integer_type("int")->get_tree(gogo);
+    }
+  else
+    {
+      // If we still have an abstract type here, then this is being
+      // used in a constant expression which didn't get reduced.  We
+      // just use float64 and hope for the best.
+      type = Type::lookup_float_type("float64")->get_tree(gogo);
+    }
+  return Expression::float_constant_tree(this->val_, type);
+}
+
+// Write a floating point number to export data.
+
+void
+Float_expression::export_float(Export *exp, const mpfr_t val)
+{
+  mp_exp_t exponent;
+  char* s = mpfr_get_str(NULL, &exponent, 10, 0, val, GMP_RNDN);
+  if (*s == '-')
+    exp->write_c_string("-");
+  exp->write_c_string("0.");
+  exp->write_c_string(*s == '-' ? s + 1 : s);
+  mpfr_free_str(s);
+  char buf[30];
+  snprintf(buf, sizeof buf, "E%ld", exponent);
+  exp->write_c_string(buf);
+}
+
+// Export a floating point number in a constant expression.
+
+void
+Float_expression::do_export(Export* exp) const
+{
+  Float_expression::export_float(exp, this->val_);
+  // A trailing space lets us reliably identify the end of the number.
+  exp->write_c_string(" ");
+}
+
+// Make a float expression.
+
+Expression*
+Expression::make_float(const mpfr_t* val, Type* type, source_location location)
+{
+  return new Float_expression(val, type, location);
+}
+
+// Complex numbers.
+
+class Complex_expression : public Expression
+{
+ public:
+  Complex_expression(const mpfr_t* real, const mpfr_t* imag, Type* type,
+		     source_location location)
+    : Expression(EXPRESSION_COMPLEX, location),
+      type_(type)
+  {
+    mpfr_init_set(this->real_, *real, GMP_RNDN);
+    mpfr_init_set(this->imag_, *imag, GMP_RNDN);
+  }
+
+  // Constrain REAL/IMAG to fit into TYPE.
+  static void
+  constrain_complex(mpfr_t real, mpfr_t imag, Type* type);
+
+  // Return whether REAL/IMAG fits in the type.
+  static bool
+  check_constant(mpfr_t real, mpfr_t imag, Type*, source_location);
+
+  // Write REAL/IMAG to export data.
+  static void
+  export_complex(Export* exp, const mpfr_t real, const mpfr_t val);
+
+ protected:
+  bool
+  do_is_constant() const
+  { return true; }
+
+  bool
+  do_complex_constant_value(mpfr_t real, mpfr_t imag, Type**) const;
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return Expression::make_complex(&this->real_, &this->imag_, this->type_,
+				    this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context*);
+
+  void
+  do_export(Export*) const;
+
+ private:
+  // The real part.
+  mpfr_t real_;
+  // The imaginary part;
+  mpfr_t imag_;
+  // The type if known.
+  Type* type_;
+};
+
+// Constrain REAL/IMAG to fit into TYPE.
+
+void
+Complex_expression::constrain_complex(mpfr_t real, mpfr_t imag, Type* type)
+{
+  Complex_type* ctype = type->complex_type();
+  if (ctype != NULL && !ctype->is_abstract())
+    {
+      tree type_tree = ctype->type_tree();
+
+      REAL_VALUE_TYPE rvt;
+      real_from_mpfr(&rvt, real, TREE_TYPE(type_tree), GMP_RNDN);
+      real_convert(&rvt, TYPE_MODE(TREE_TYPE(type_tree)), &rvt);
+      mpfr_from_real(real, &rvt, GMP_RNDN);
+
+      real_from_mpfr(&rvt, imag, TREE_TYPE(type_tree), GMP_RNDN);
+      real_convert(&rvt, TYPE_MODE(TREE_TYPE(type_tree)), &rvt);
+      mpfr_from_real(imag, &rvt, GMP_RNDN);
+    }
+}
+
+// Return a complex constant value.
+
+bool
+Complex_expression::do_complex_constant_value(mpfr_t real, mpfr_t imag,
+					      Type** ptype) const
+{
+  if (this->type_ != NULL)
+    *ptype = this->type_;
+  mpfr_set(real, this->real_, GMP_RNDN);
+  mpfr_set(imag, this->imag_, GMP_RNDN);
+  return true;
+}
+
+// Return the current type.  If we haven't set the type yet, we return
+// an abstract complex type.
+
+Type*
+Complex_expression::do_type()
+{
+  if (this->type_ == NULL)
+    this->type_ = Type::make_abstract_complex_type();
+  return this->type_;
+}
+
+// Set the type of the complex value.  Here we may switch from an
+// abstract type to a real type.
+
+void
+Complex_expression::do_determine_type(const Type_context* context)
+{
+  if (this->type_ != NULL && !this->type_->is_abstract())
+    ;
+  else if (context->type != NULL
+	   && context->type->complex_type() != NULL)
+    this->type_ = context->type;
+  else if (!context->may_be_abstract)
+    this->type_ = Type::lookup_complex_type("complex128");
+}
+
+// Return true if the complex value REAL/IMAG fits in the range of the
+// type TYPE.  Otherwise give an error and return false.  TYPE may be
+// NULL.
+
+bool
+Complex_expression::check_constant(mpfr_t real, mpfr_t imag, Type* type,
+				   source_location location)
+{
+  if (type == NULL)
+    return true;
+  Complex_type* ctype = type->complex_type();
+  if (ctype == NULL || ctype->is_abstract())
+    return true;
+
+  mp_exp_t max_exp;
+  switch (ctype->bits())
+    {
+    case 64:
+      max_exp = 128;
+      break;
+    case 128:
+      max_exp = 1024;
+      break;
+    default:
+      gcc_unreachable();
+    }
+
+  // A NaN or Infinity always fits in the range of the type.
+  if (!mpfr_nan_p(real) && !mpfr_inf_p(real) && !mpfr_zero_p(real))
+    {
+      if (mpfr_get_exp(real) > max_exp)
+	{
+	  error_at(location, "complex real part constant overflow");
+	  return false;
+	}
+    }
+
+  if (!mpfr_nan_p(imag) && !mpfr_inf_p(imag) && !mpfr_zero_p(imag))
+    {
+      if (mpfr_get_exp(imag) > max_exp)
+	{
+	  error_at(location, "complex imaginary part constant overflow");
+	  return false;
+	}
+    }
+
+  return true;
+}
+
+// Check the type of a complex value.
+
+void
+Complex_expression::do_check_types(Gogo*)
+{
+  if (this->type_ == NULL)
+    return;
+
+  if (!Complex_expression::check_constant(this->real_, this->imag_,
+					  this->type_, this->location()))
+    this->set_is_error();
+}
+
+// Get a tree for a complex constant.
+
+tree
+Complex_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  tree type;
+  if (this->type_ != NULL && !this->type_->is_abstract())
+    type = this->type_->get_tree(gogo);
+  else
+    {
+      // If we still have an abstract type here, this this is being
+      // used in a constant expression which didn't get reduced.  We
+      // just use complex128 and hope for the best.
+      type = Type::lookup_complex_type("complex128")->get_tree(gogo);
+    }
+  return Expression::complex_constant_tree(this->real_, this->imag_, type);
+}
+
+// Write REAL/IMAG to export data.
+
+void
+Complex_expression::export_complex(Export* exp, const mpfr_t real,
+				   const mpfr_t imag)
+{
+  if (!mpfr_zero_p(real))
+    {
+      Float_expression::export_float(exp, real);
+      if (mpfr_sgn(imag) > 0)
+	exp->write_c_string("+");
+    }
+  Float_expression::export_float(exp, imag);
+  exp->write_c_string("i");
+}
+
+// Export a complex number in a constant expression.
+
+void
+Complex_expression::do_export(Export* exp) const
+{
+  Complex_expression::export_complex(exp, this->real_, this->imag_);
+  // A trailing space lets us reliably identify the end of the number.
+  exp->write_c_string(" ");
+}
+
+// Make a complex expression.
+
+Expression*
+Expression::make_complex(const mpfr_t* real, const mpfr_t* imag, Type* type,
+			 source_location location)
+{
+  return new Complex_expression(real, imag, type, location);
+}
+
+// Find a named object in an expression.
+
+class Find_named_object : public Traverse
+{
+ public:
+  Find_named_object(Named_object* no)
+    : Traverse(traverse_expressions),
+      no_(no), found_(false)
+  { }
+
+  // Whether we found the object.
+  bool
+  found() const
+  { return this->found_; }
+
+ protected:
+  int
+  expression(Expression**);
+
+ private:
+  // The object we are looking for.
+  Named_object* no_;
+  // Whether we found it.
+  bool found_;
+};
+
+// A reference to a const in an expression.
+
+class Const_expression : public Expression
+{
+ public:
+  Const_expression(Named_object* constant, source_location location)
+    : Expression(EXPRESSION_CONST_REFERENCE, location),
+      constant_(constant), type_(NULL), seen_(false)
+  { }
+
+  Named_object*
+  named_object()
+  { return this->constant_; }
+
+  // Check that the initializer does not refer to the constant itself.
+  void
+  check_for_init_loop();
+
+ protected:
+  int
+  do_traverse(Traverse*);
+
+  Expression*
+  do_lower(Gogo*, Named_object*, int);
+
+  bool
+  do_is_constant() const
+  { return true; }
+
+  bool
+  do_integer_constant_value(bool, mpz_t val, Type**) const;
+
+  bool
+  do_float_constant_value(mpfr_t val, Type**) const;
+
+  bool
+  do_complex_constant_value(mpfr_t real, mpfr_t imag, Type**) const;
+
+  bool
+  do_string_constant_value(std::string* val) const
+  { return this->constant_->const_value()->expr()->string_constant_value(val); }
+
+  Type*
+  do_type();
+
+  // The type of a const is set by the declaration, not the use.
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  { return this; }
+
+  tree
+  do_get_tree(Translate_context* context);
+
+  // When exporting a reference to a const as part of a const
+  // expression, we export the value.  We ignore the fact that it has
+  // a name.
+  void
+  do_export(Export* exp) const
+  { this->constant_->const_value()->expr()->export_expression(exp); }
+
+ private:
+  // The constant.
+  Named_object* constant_;
+  // The type of this reference.  This is used if the constant has an
+  // abstract type.
+  Type* type_;
+  // Used to prevent infinite recursion when a constant incorrectly
+  // refers to itself.
+  mutable bool seen_;
+};
+
+// Traversal.
+
+int
+Const_expression::do_traverse(Traverse* traverse)
+{
+  if (this->type_ != NULL)
+    return Type::traverse(this->type_, traverse);
+  return TRAVERSE_CONTINUE;
+}
+
+// Lower a constant expression.  This is where we convert the
+// predeclared constant iota into an integer value.
+
+Expression*
+Const_expression::do_lower(Gogo* gogo, Named_object*, int iota_value)
+{
+  if (this->constant_->const_value()->expr()->classification()
+      == EXPRESSION_IOTA)
+    {
+      if (iota_value == -1)
+	{
+	  error_at(this->location(),
+		   "iota is only defined in const declarations");
+	  iota_value = 0;
+	}
+      mpz_t val;
+      mpz_init_set_ui(val, static_cast<unsigned long>(iota_value));
+      Expression* ret = Expression::make_integer(&val, NULL,
+						 this->location());
+      mpz_clear(val);
+      return ret;
+    }
+
+  // Make sure that the constant itself has been lowered.
+  gogo->lower_constant(this->constant_);
+
+  return this;
+}
+
+// Return an integer constant value.
+
+bool
+Const_expression::do_integer_constant_value(bool iota_is_constant, mpz_t val,
+					    Type** ptype) const
+{
+  if (this->seen_)
+    return false;
+
+  Type* ctype;
+  if (this->type_ != NULL)
+    ctype = this->type_;
+  else
+    ctype = this->constant_->const_value()->type();
+  if (ctype != NULL && ctype->integer_type() == NULL)
+    return false;
+
+  Expression* e = this->constant_->const_value()->expr();
+
+  this->seen_ = true;
+
+  Type* t;
+  bool r = e->integer_constant_value(iota_is_constant, val, &t);
+
+  this->seen_ = false;
+
+  if (r
+      && ctype != NULL
+      && !Integer_expression::check_constant(val, ctype, this->location()))
+    return false;
+
+  *ptype = ctype != NULL ? ctype : t;
+  return r;
+}
+
+// Return a floating point constant value.
+
+bool
+Const_expression::do_float_constant_value(mpfr_t val, Type** ptype) const
+{
+  if (this->seen_)
+    return false;
+
+  Type* ctype;
+  if (this->type_ != NULL)
+    ctype = this->type_;
+  else
+    ctype = this->constant_->const_value()->type();
+  if (ctype != NULL && ctype->float_type() == NULL)
+    return false;
+
+  this->seen_ = true;
+
+  Type* t;
+  bool r = this->constant_->const_value()->expr()->float_constant_value(val,
+									&t);
+
+  this->seen_ = false;
+
+  if (r && ctype != NULL)
+    {
+      if (!Float_expression::check_constant(val, ctype, this->location()))
+	return false;
+      Float_expression::constrain_float(val, ctype);
+    }
+  *ptype = ctype != NULL ? ctype : t;
+  return r;
+}
+
+// Return a complex constant value.
+
+bool
+Const_expression::do_complex_constant_value(mpfr_t real, mpfr_t imag,
+					    Type **ptype) const
+{
+  if (this->seen_)
+    return false;
+
+  Type* ctype;
+  if (this->type_ != NULL)
+    ctype = this->type_;
+  else
+    ctype = this->constant_->const_value()->type();
+  if (ctype != NULL && ctype->complex_type() == NULL)
+    return false;
+
+  this->seen_ = true;
+
+  Type *t;
+  bool r = this->constant_->const_value()->expr()->complex_constant_value(real,
+									  imag,
+									  &t);
+
+  this->seen_ = false;
+
+  if (r && ctype != NULL)
+    {
+      if (!Complex_expression::check_constant(real, imag, ctype,
+					      this->location()))
+	return false;
+      Complex_expression::constrain_complex(real, imag, ctype);
+    }
+  *ptype = ctype != NULL ? ctype : t;
+  return r;
+}
+
+// Return the type of the const reference.
+
+Type*
+Const_expression::do_type()
+{
+  if (this->type_ != NULL)
+    return this->type_;
+
+  Named_constant* nc = this->constant_->const_value();
+
+  if (this->seen_ || nc->lowering())
+    {
+      this->report_error(_("constant refers to itself"));
+      this->type_ = Type::make_error_type();
+      return this->type_;
+    }
+
+  this->seen_ = true;
+
+  Type* ret = nc->type();
+
+  if (ret != NULL)
+    {
+      this->seen_ = false;
+      return ret;
+    }
+
+  // During parsing, a named constant may have a NULL type, but we
+  // must not return a NULL type here.
+  ret = nc->expr()->type();
+
+  this->seen_ = false;
+
+  return ret;
+}
+
+// Set the type of the const reference.
+
+void
+Const_expression::do_determine_type(const Type_context* context)
+{
+  Type* ctype = this->constant_->const_value()->type();
+  Type* cetype = (ctype != NULL
+		  ? ctype
+		  : this->constant_->const_value()->expr()->type());
+  if (ctype != NULL && !ctype->is_abstract())
+    ;
+  else if (context->type != NULL
+	   && (context->type->integer_type() != NULL
+	       || context->type->float_type() != NULL
+	       || context->type->complex_type() != NULL)
+	   && (cetype->integer_type() != NULL
+	       || cetype->float_type() != NULL
+	       || cetype->complex_type() != NULL))
+    this->type_ = context->type;
+  else if (context->type != NULL
+	   && context->type->is_string_type()
+	   && cetype->is_string_type())
+    this->type_ = context->type;
+  else if (context->type != NULL
+	   && context->type->is_boolean_type()
+	   && cetype->is_boolean_type())
+    this->type_ = context->type;
+  else if (!context->may_be_abstract)
+    {
+      if (cetype->is_abstract())
+	cetype = cetype->make_non_abstract_type();
+      this->type_ = cetype;
+    }
+}
+
+// Check for a loop in which the initializer of a constant refers to
+// the constant itself.
+
+void
+Const_expression::check_for_init_loop()
+{
+  if (this->type_ != NULL && this->type_->is_error_type())
+    return;
+
+  if (this->seen_)
+    {
+      this->report_error(_("constant refers to itself"));
+      this->type_ = Type::make_error_type();
+      return;
+    }
+
+  Expression* init = this->constant_->const_value()->expr();
+  Find_named_object find_named_object(this->constant_);
+
+  this->seen_ = true;
+  Expression::traverse(&init, &find_named_object);
+  this->seen_ = false;
+
+  if (find_named_object.found())
+    {
+      if (this->type_ == NULL || !this->type_->is_error_type())
+	{
+	  this->report_error(_("constant refers to itself"));
+	  this->type_ = Type::make_error_type();
+	}
+      return;
+    }
+}
+
+// Check types of a const reference.
+
+void
+Const_expression::do_check_types(Gogo*)
+{
+  if (this->type_ != NULL && this->type_->is_error_type())
+    return;
+
+  this->check_for_init_loop();
+
+  if (this->type_ == NULL || this->type_->is_abstract())
+    return;
+
+  // Check for integer overflow.
+  if (this->type_->integer_type() != NULL)
+    {
+      mpz_t ival;
+      mpz_init(ival);
+      Type* dummy;
+      if (!this->integer_constant_value(true, ival, &dummy))
+	{
+	  mpfr_t fval;
+	  mpfr_init(fval);
+	  Expression* cexpr = this->constant_->const_value()->expr();
+	  if (cexpr->float_constant_value(fval, &dummy))
+	    {
+	      if (!mpfr_integer_p(fval))
+		this->report_error(_("floating point constant "
+				     "truncated to integer"));
+	      else
+		{
+		  mpfr_get_z(ival, fval, GMP_RNDN);
+		  Integer_expression::check_constant(ival, this->type_,
+						     this->location());
+		}
+	    }
+	  mpfr_clear(fval);
+	}
+      mpz_clear(ival);
+    }
+}
+
+// Return a tree for the const reference.
+
+tree
+Const_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  tree type_tree;
+  if (this->type_ == NULL)
+    type_tree = NULL_TREE;
+  else
+    {
+      type_tree = this->type_->get_tree(gogo);
+      if (type_tree == error_mark_node)
+	return error_mark_node;
+    }
+
+  // If the type has been set for this expression, but the underlying
+  // object is an abstract int or float, we try to get the abstract
+  // value.  Otherwise we may lose something in the conversion.
+  if (this->type_ != NULL
+      && (this->constant_->const_value()->type() == NULL
+	  || this->constant_->const_value()->type()->is_abstract()))
+    {
+      Expression* expr = this->constant_->const_value()->expr();
+      mpz_t ival;
+      mpz_init(ival);
+      Type* t;
+      if (expr->integer_constant_value(true, ival, &t))
+	{
+	  tree ret = Expression::integer_constant_tree(ival, type_tree);
+	  mpz_clear(ival);
+	  return ret;
+	}
+      mpz_clear(ival);
+
+      mpfr_t fval;
+      mpfr_init(fval);
+      if (expr->float_constant_value(fval, &t))
+	{
+	  tree ret = Expression::float_constant_tree(fval, type_tree);
+	  mpfr_clear(fval);
+	  return ret;
+	}
+
+      mpfr_t imag;
+      mpfr_init(imag);
+      if (expr->complex_constant_value(fval, imag, &t))
+	{
+	  tree ret = Expression::complex_constant_tree(fval, imag, type_tree);
+	  mpfr_clear(fval);
+	  mpfr_clear(imag);
+	  return ret;
+	}
+      mpfr_clear(imag);
+      mpfr_clear(fval);
+    }
+
+  tree const_tree = this->constant_->get_tree(gogo, context->function());
+  if (this->type_ == NULL
+      || const_tree == error_mark_node
+      || TREE_TYPE(const_tree) == error_mark_node)
+    return const_tree;
+
+  tree ret;
+  if (TYPE_MAIN_VARIANT(type_tree) == TYPE_MAIN_VARIANT(TREE_TYPE(const_tree)))
+    ret = fold_convert(type_tree, const_tree);
+  else if (TREE_CODE(type_tree) == INTEGER_TYPE)
+    ret = fold(convert_to_integer(type_tree, const_tree));
+  else if (TREE_CODE(type_tree) == REAL_TYPE)
+    ret = fold(convert_to_real(type_tree, const_tree));
+  else if (TREE_CODE(type_tree) == COMPLEX_TYPE)
+    ret = fold(convert_to_complex(type_tree, const_tree));
+  else
+    gcc_unreachable();
+  return ret;
+}
+
+// Make a reference to a constant in an expression.
+
+Expression*
+Expression::make_const_reference(Named_object* constant,
+				 source_location location)
+{
+  return new Const_expression(constant, location);
+}
+
+// Find a named object in an expression.
+
+int
+Find_named_object::expression(Expression** pexpr)
+{
+  switch ((*pexpr)->classification())
+    {
+    case Expression::EXPRESSION_CONST_REFERENCE:
+      {
+	Const_expression* ce = static_cast<Const_expression*>(*pexpr);
+	if (ce->named_object() == this->no_)
+	  break;
+
+	// We need to check a constant initializer explicitly, as
+	// loops here will not be caught by the loop checking for
+	// variable initializers.
+	ce->check_for_init_loop();
+
+	return TRAVERSE_CONTINUE;
+      }
+
+    case Expression::EXPRESSION_VAR_REFERENCE:
+      if ((*pexpr)->var_expression()->named_object() == this->no_)
+	break;
+      return TRAVERSE_CONTINUE;
+    case Expression::EXPRESSION_FUNC_REFERENCE:
+      if ((*pexpr)->func_expression()->named_object() == this->no_)
+	break;
+      return TRAVERSE_CONTINUE;
+    default:
+      return TRAVERSE_CONTINUE;
+    }
+  this->found_ = true;
+  return TRAVERSE_EXIT;
+}
+
+// The nil value.
+
+class Nil_expression : public Expression
+{
+ public:
+  Nil_expression(source_location location)
+    : Expression(EXPRESSION_NIL, location)
+  { }
+
+  static Expression*
+  do_import(Import*);
+
+ protected:
+  bool
+  do_is_constant() const
+  { return true; }
+
+  Type*
+  do_type()
+  { return Type::make_nil_type(); }
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  Expression*
+  do_copy()
+  { return this; }
+
+  tree
+  do_get_tree(Translate_context*)
+  { return null_pointer_node; }
+
+  void
+  do_export(Export* exp) const
+  { exp->write_c_string("nil"); }
+};
+
+// Import a nil expression.
+
+Expression*
+Nil_expression::do_import(Import* imp)
+{
+  imp->require_c_string("nil");
+  return Expression::make_nil(imp->location());
+}
+
+// Make a nil expression.
+
+Expression*
+Expression::make_nil(source_location location)
+{
+  return new Nil_expression(location);
+}
+
+// The value of the predeclared constant iota.  This is little more
+// than a marker.  This will be lowered to an integer in
+// Const_expression::do_lower, which is where we know the value that
+// it should have.
+
+class Iota_expression : public Parser_expression
+{
+ public:
+  Iota_expression(source_location location)
+    : Parser_expression(EXPRESSION_IOTA, location)
+  { }
+
+ protected:
+  Expression*
+  do_lower(Gogo*, Named_object*, int)
+  { gcc_unreachable(); }
+
+  // There should only ever be one of these.
+  Expression*
+  do_copy()
+  { gcc_unreachable(); }
+};
+
+// Make an iota expression.  This is only called for one case: the
+// value of the predeclared constant iota.
+
+Expression*
+Expression::make_iota()
+{
+  static Iota_expression iota_expression(UNKNOWN_LOCATION);
+  return &iota_expression;
+}
+
+// A type conversion expression.
+
+class Type_conversion_expression : public Expression
+{
+ public:
+  Type_conversion_expression(Type* type, Expression* expr,
+			     source_location location)
+    : Expression(EXPRESSION_CONVERSION, location),
+      type_(type), expr_(expr), may_convert_function_types_(false)
+  { }
+
+  // Return the type to which we are converting.
+  Type*
+  type() const
+  { return this->type_; }
+
+  // Return the expression which we are converting.
+  Expression*
+  expr() const
+  { return this->expr_; }
+
+  // Permit converting from one function type to another.  This is
+  // used internally for method expressions.
+  void
+  set_may_convert_function_types()
+  {
+    this->may_convert_function_types_ = true;
+  }
+
+  // Import a type conversion expression.
+  static Expression*
+  do_import(Import*);
+
+ protected:
+  int
+  do_traverse(Traverse* traverse);
+
+  Expression*
+  do_lower(Gogo*, Named_object*, int);
+
+  bool
+  do_is_constant() const
+  { return this->expr_->is_constant(); }
+
+  bool
+  do_integer_constant_value(bool, mpz_t, Type**) const;
+
+  bool
+  do_float_constant_value(mpfr_t, Type**) const;
+
+  bool
+  do_complex_constant_value(mpfr_t, mpfr_t, Type**) const;
+
+  bool
+  do_string_constant_value(std::string*) const;
+
+  Type*
+  do_type()
+  { return this->type_; }
+
+  void
+  do_determine_type(const Type_context*)
+  {
+    Type_context subcontext(this->type_, false);
+    this->expr_->determine_type(&subcontext);
+  }
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return new Type_conversion_expression(this->type_, this->expr_->copy(),
+					  this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context* context);
+
+  void
+  do_export(Export*) const;
+
+ private:
+  // The type to convert to.
+  Type* type_;
+  // The expression to convert.
+  Expression* expr_;
+  // True if this is permitted to convert function types.  This is
+  // used internally for method expressions.
+  bool may_convert_function_types_;
+};
+
+// Traversal.
+
+int
+Type_conversion_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->expr_, traverse) == TRAVERSE_EXIT
+      || Type::traverse(this->type_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return TRAVERSE_CONTINUE;
+}
+
+// Convert to a constant at lowering time.
+
+Expression*
+Type_conversion_expression::do_lower(Gogo*, Named_object*, int)
+{
+  Type* type = this->type_;
+  Expression* val = this->expr_;
+  source_location location = this->location();
+
+  if (type->integer_type() != NULL)
+    {
+      mpz_t ival;
+      mpz_init(ival);
+      Type* dummy;
+      if (val->integer_constant_value(false, ival, &dummy))
+	{
+	  if (!Integer_expression::check_constant(ival, type, location))
+	    mpz_set_ui(ival, 0);
+	  Expression* ret = Expression::make_integer(&ival, type, location);
+	  mpz_clear(ival);
+	  return ret;
+	}
+
+      mpfr_t fval;
+      mpfr_init(fval);
+      if (val->float_constant_value(fval, &dummy))
+	{
+	  if (!mpfr_integer_p(fval))
+	    {
+	      error_at(location,
+		       "floating point constant truncated to integer");
+	      return Expression::make_error(location);
+	    }
+	  mpfr_get_z(ival, fval, GMP_RNDN);
+	  if (!Integer_expression::check_constant(ival, type, location))
+	    mpz_set_ui(ival, 0);
+	  Expression* ret = Expression::make_integer(&ival, type, location);
+	  mpfr_clear(fval);
+	  mpz_clear(ival);
+	  return ret;
+	}
+      mpfr_clear(fval);
+      mpz_clear(ival);
+    }
+
+  if (type->float_type() != NULL)
+    {
+      mpfr_t fval;
+      mpfr_init(fval);
+      Type* dummy;
+      if (val->float_constant_value(fval, &dummy))
+	{
+	  if (!Float_expression::check_constant(fval, type, location))
+	    mpfr_set_ui(fval, 0, GMP_RNDN);
+	  Float_expression::constrain_float(fval, type);
+	  Expression *ret = Expression::make_float(&fval, type, location);
+	  mpfr_clear(fval);
+	  return ret;
+	}
+      mpfr_clear(fval);
+    }
+
+  if (type->complex_type() != NULL)
+    {
+      mpfr_t real;
+      mpfr_t imag;
+      mpfr_init(real);
+      mpfr_init(imag);
+      Type* dummy;
+      if (val->complex_constant_value(real, imag, &dummy))
+	{
+	  if (!Complex_expression::check_constant(real, imag, type, location))
+	    {
+	      mpfr_set_ui(real, 0, GMP_RNDN);
+	      mpfr_set_ui(imag, 0, GMP_RNDN);
+	    }
+	  Complex_expression::constrain_complex(real, imag, type);
+	  Expression* ret = Expression::make_complex(&real, &imag, type,
+						     location);
+	  mpfr_clear(real);
+	  mpfr_clear(imag);
+	  return ret;
+	}
+      mpfr_clear(real);
+      mpfr_clear(imag);
+    }
+
+  if (type->is_open_array_type() && type->named_type() == NULL)
+    {
+      Type* element_type = type->array_type()->element_type()->forwarded();
+      bool is_byte = element_type == Type::lookup_integer_type("uint8");
+      bool is_int = element_type == Type::lookup_integer_type("int");
+      if (is_byte || is_int)
+	{
+	  std::string s;
+	  if (val->string_constant_value(&s))
+	    {
+	      Expression_list* vals = new Expression_list();
+	      if (is_byte)
+		{
+		  for (std::string::const_iterator p = s.begin();
+		       p != s.end();
+		       p++)
+		    {
+		      mpz_t val;
+		      mpz_init_set_ui(val, static_cast<unsigned char>(*p));
+		      Expression* v = Expression::make_integer(&val,
+							       element_type,
+							       location);
+		      vals->push_back(v);
+		      mpz_clear(val);
+		    }
+		}
+	      else
+		{
+		  const char *p = s.data();
+		  const char *pend = s.data() + s.length();
+		  while (p < pend)
+		    {
+		      unsigned int c;
+		      int adv = Lex::fetch_char(p, &c);
+		      if (adv == 0)
+			{
+			  warning_at(this->location(), 0,
+				     "invalid UTF-8 encoding");
+			  adv = 1;
+			}
+		      p += adv;
+		      mpz_t val;
+		      mpz_init_set_ui(val, c);
+		      Expression* v = Expression::make_integer(&val,
+							       element_type,
+							       location);
+		      vals->push_back(v);
+		      mpz_clear(val);
+		    }
+		}
+
+	      return Expression::make_slice_composite_literal(type, vals,
+							      location);
+	    }
+	}
+    }
+
+  return this;
+}
+
+// Return the constant integer value if there is one.
+
+bool
+Type_conversion_expression::do_integer_constant_value(bool iota_is_constant,
+						      mpz_t val,
+						      Type** ptype) const
+{
+  if (this->type_->integer_type() == NULL)
+    return false;
+
+  mpz_t ival;
+  mpz_init(ival);
+  Type* dummy;
+  if (this->expr_->integer_constant_value(iota_is_constant, ival, &dummy))
+    {
+      if (!Integer_expression::check_constant(ival, this->type_,
+					      this->location()))
+	{
+	  mpz_clear(ival);
+	  return false;
+	}
+      mpz_set(val, ival);
+      mpz_clear(ival);
+      *ptype = this->type_;
+      return true;
+    }
+  mpz_clear(ival);
+
+  mpfr_t fval;
+  mpfr_init(fval);
+  if (this->expr_->float_constant_value(fval, &dummy))
+    {
+      mpfr_get_z(val, fval, GMP_RNDN);
+      mpfr_clear(fval);
+      if (!Integer_expression::check_constant(val, this->type_,
+					      this->location()))
+	return false;
+      *ptype = this->type_;
+      return true;
+    }
+  mpfr_clear(fval);
+
+  return false;
+}
+
+// Return the constant floating point value if there is one.
+
+bool
+Type_conversion_expression::do_float_constant_value(mpfr_t val,
+						    Type** ptype) const
+{
+  if (this->type_->float_type() == NULL)
+    return false;
+
+  mpfr_t fval;
+  mpfr_init(fval);
+  Type* dummy;
+  if (this->expr_->float_constant_value(fval, &dummy))
+    {
+      if (!Float_expression::check_constant(fval, this->type_,
+					    this->location()))
+	{
+	  mpfr_clear(fval);
+	  return false;
+	}
+      mpfr_set(val, fval, GMP_RNDN);
+      mpfr_clear(fval);
+      Float_expression::constrain_float(val, this->type_);
+      *ptype = this->type_;
+      return true;
+    }
+  mpfr_clear(fval);
+
+  return false;
+}
+
+// Return the constant complex value if there is one.
+
+bool
+Type_conversion_expression::do_complex_constant_value(mpfr_t real,
+						      mpfr_t imag,
+						      Type **ptype) const
+{
+  if (this->type_->complex_type() == NULL)
+    return false;
+
+  mpfr_t rval;
+  mpfr_t ival;
+  mpfr_init(rval);
+  mpfr_init(ival);
+  Type* dummy;
+  if (this->expr_->complex_constant_value(rval, ival, &dummy))
+    {
+      if (!Complex_expression::check_constant(rval, ival, this->type_,
+					      this->location()))
+	{
+	  mpfr_clear(rval);
+	  mpfr_clear(ival);
+	  return false;
+	}
+      mpfr_set(real, rval, GMP_RNDN);
+      mpfr_set(imag, ival, GMP_RNDN);
+      mpfr_clear(rval);
+      mpfr_clear(ival);
+      Complex_expression::constrain_complex(real, imag, this->type_);
+      *ptype = this->type_;
+      return true;
+    }
+  mpfr_clear(rval);
+  mpfr_clear(ival);
+
+  return false;  
+}
+
+// Return the constant string value if there is one.
+
+bool
+Type_conversion_expression::do_string_constant_value(std::string* val) const
+{
+  if (this->type_->is_string_type()
+      && this->expr_->type()->integer_type() != NULL)
+    {
+      mpz_t ival;
+      mpz_init(ival);
+      Type* dummy;
+      if (this->expr_->integer_constant_value(false, ival, &dummy))
+	{
+	  unsigned long ulval = mpz_get_ui(ival);
+	  if (mpz_cmp_ui(ival, ulval) == 0)
+	    {
+	      Lex::append_char(ulval, true, val, this->location());
+	      mpz_clear(ival);
+	      return true;
+	    }
+	}
+      mpz_clear(ival);
+    }
+
+  // FIXME: Could handle conversion from const []int here.
+
+  return false;
+}
+
+// Check that types are convertible.
+
+void
+Type_conversion_expression::do_check_types(Gogo*)
+{
+  Type* type = this->type_;
+  Type* expr_type = this->expr_->type();
+  std::string reason;
+
+  if (type->is_error_type()
+      || type->is_undefined()
+      || expr_type->is_error_type()
+      || expr_type->is_undefined())
+    {
+      // Make sure we emit an error for an undefined type.
+      type->base();
+      expr_type->base();
+      this->set_is_error();
+      return;
+    }
+
+  if (this->may_convert_function_types_
+      && type->function_type() != NULL
+      && expr_type->function_type() != NULL)
+    return;
+
+  if (Type::are_convertible(type, expr_type, &reason))
+    return;
+
+  error_at(this->location(), "%s", reason.c_str());
+  this->set_is_error();
+}
+
+// Get a tree for a type conversion.
+
+tree
+Type_conversion_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  tree type_tree = this->type_->get_tree(gogo);
+  tree expr_tree = this->expr_->get_tree(context);
+
+  if (type_tree == error_mark_node
+      || expr_tree == error_mark_node
+      || TREE_TYPE(expr_tree) == error_mark_node)
+    return error_mark_node;
+
+  if (TYPE_MAIN_VARIANT(type_tree) == TYPE_MAIN_VARIANT(TREE_TYPE(expr_tree)))
+    return fold_convert(type_tree, expr_tree);
+
+  Type* type = this->type_;
+  Type* expr_type = this->expr_->type();
+  tree ret;
+  if (type->interface_type() != NULL || expr_type->interface_type() != NULL)
+    ret = Expression::convert_for_assignment(context, type, expr_type,
+					     expr_tree, this->location());
+  else if (type->integer_type() != NULL)
+    {
+      if (expr_type->integer_type() != NULL
+	  || expr_type->float_type() != NULL
+	  || expr_type->is_unsafe_pointer_type())
+	ret = fold(convert_to_integer(type_tree, expr_tree));
+      else
+	gcc_unreachable();
+    }
+  else if (type->float_type() != NULL)
+    {
+      if (expr_type->integer_type() != NULL
+	  || expr_type->float_type() != NULL)
+	ret = fold(convert_to_real(type_tree, expr_tree));
+      else
+	gcc_unreachable();
+    }
+  else if (type->complex_type() != NULL)
+    {
+      if (expr_type->complex_type() != NULL)
+	ret = fold(convert_to_complex(type_tree, expr_tree));
+      else
+	gcc_unreachable();
+    }
+  else if (type->is_string_type()
+	   && expr_type->integer_type() != NULL)
+    {
+      expr_tree = fold_convert(integer_type_node, expr_tree);
+      if (host_integerp(expr_tree, 0))
+	{
+	  HOST_WIDE_INT intval = tree_low_cst(expr_tree, 0);
+	  std::string s;
+	  Lex::append_char(intval, true, &s, this->location());
+	  Expression* se = Expression::make_string(s, this->location());
+	  return se->get_tree(context);
+	}
+
+      static tree int_to_string_fndecl;
+      ret = Gogo::call_builtin(&int_to_string_fndecl,
+			       this->location(),
+			       "__go_int_to_string",
+			       1,
+			       type_tree,
+			       integer_type_node,
+			       fold_convert(integer_type_node, expr_tree));
+    }
+  else if (type->is_string_type()
+	   && (expr_type->array_type() != NULL
+	       || (expr_type->points_to() != NULL
+		   && expr_type->points_to()->array_type() != NULL)))
+    {
+      Type* t = expr_type;
+      if (t->points_to() != NULL)
+	{
+	  t = t->points_to();
+	  expr_tree = build_fold_indirect_ref(expr_tree);
+	}
+      if (!DECL_P(expr_tree))
+	expr_tree = save_expr(expr_tree);
+      Array_type* a = t->array_type();
+      Type* e = a->element_type()->forwarded();
+      gcc_assert(e->integer_type() != NULL);
+      tree valptr = fold_convert(const_ptr_type_node,
+				 a->value_pointer_tree(gogo, expr_tree));
+      tree len = a->length_tree(gogo, expr_tree);
+      len = fold_convert_loc(this->location(), size_type_node, len);
+      if (e->integer_type()->is_unsigned()
+	  && e->integer_type()->bits() == 8)
+	{
+	  static tree byte_array_to_string_fndecl;
+	  ret = Gogo::call_builtin(&byte_array_to_string_fndecl,
+				   this->location(),
+				   "__go_byte_array_to_string",
+				   2,
+				   type_tree,
+				   const_ptr_type_node,
+				   valptr,
+				   size_type_node,
+				   len);
+	}
+      else
+	{
+	  gcc_assert(e == Type::lookup_integer_type("int"));
+	  static tree int_array_to_string_fndecl;
+	  ret = Gogo::call_builtin(&int_array_to_string_fndecl,
+				   this->location(),
+				   "__go_int_array_to_string",
+				   2,
+				   type_tree,
+				   const_ptr_type_node,
+				   valptr,
+				   size_type_node,
+				   len);
+	}
+    }
+  else if (type->is_open_array_type() && expr_type->is_string_type())
+    {
+      Type* e = type->array_type()->element_type()->forwarded();
+      gcc_assert(e->integer_type() != NULL);
+      if (e->integer_type()->is_unsigned()
+	  && e->integer_type()->bits() == 8)
+	{
+	  static tree string_to_byte_array_fndecl;
+	  ret = Gogo::call_builtin(&string_to_byte_array_fndecl,
+				   this->location(),
+				   "__go_string_to_byte_array",
+				   1,
+				   type_tree,
+				   TREE_TYPE(expr_tree),
+				   expr_tree);
+	}
+      else
+	{
+	  gcc_assert(e == Type::lookup_integer_type("int"));
+	  static tree string_to_int_array_fndecl;
+	  ret = Gogo::call_builtin(&string_to_int_array_fndecl,
+				   this->location(),
+				   "__go_string_to_int_array",
+				   1,
+				   type_tree,
+				   TREE_TYPE(expr_tree),
+				   expr_tree);
+	}
+    }
+  else if ((type->is_unsafe_pointer_type()
+	    && expr_type->points_to() != NULL)
+	   || (expr_type->is_unsafe_pointer_type()
+	       && type->points_to() != NULL))
+    ret = fold_convert(type_tree, expr_tree);
+  else if (type->is_unsafe_pointer_type()
+	   && expr_type->integer_type() != NULL)
+    ret = convert_to_pointer(type_tree, expr_tree);
+  else if (this->may_convert_function_types_
+	   && type->function_type() != NULL
+	   && expr_type->function_type() != NULL)
+    ret = fold_convert_loc(this->location(), type_tree, expr_tree);
+  else
+    ret = Expression::convert_for_assignment(context, type, expr_type,
+					     expr_tree, this->location());
+
+  return ret;
+}
+
+// Output a type conversion in a constant expression.
+
+void
+Type_conversion_expression::do_export(Export* exp) const
+{
+  exp->write_c_string("convert(");
+  exp->write_type(this->type_);
+  exp->write_c_string(", ");
+  this->expr_->export_expression(exp);
+  exp->write_c_string(")");
+}
+
+// Import a type conversion or a struct construction.
+
+Expression*
+Type_conversion_expression::do_import(Import* imp)
+{
+  imp->require_c_string("convert(");
+  Type* type = imp->read_type();
+  imp->require_c_string(", ");
+  Expression* val = Expression::import_expression(imp);
+  imp->require_c_string(")");
+  return Expression::make_cast(type, val, imp->location());
+}
+
+// Make a type cast expression.
+
+Expression*
+Expression::make_cast(Type* type, Expression* val, source_location location)
+{
+  if (type->is_error_type() || val->is_error_expression())
+    return Expression::make_error(location);
+  return new Type_conversion_expression(type, val, location);
+}
+
+// Unary expressions.
+
+class Unary_expression : public Expression
+{
+ public:
+  Unary_expression(Operator op, Expression* expr, source_location location)
+    : Expression(EXPRESSION_UNARY, location),
+      op_(op), escapes_(true), expr_(expr)
+  { }
+
+  // Return the operator.
+  Operator
+  op() const
+  { return this->op_; }
+
+  // Return the operand.
+  Expression*
+  operand() const
+  { return this->expr_; }
+
+  // Record that an address expression does not escape.
+  void
+  set_does_not_escape()
+  {
+    gcc_assert(this->op_ == OPERATOR_AND);
+    this->escapes_ = false;
+  }
+
+  // Apply unary opcode OP to UVAL, setting VAL.  Return true if this
+  // could be done, false if not.
+  static bool
+  eval_integer(Operator op, Type* utype, mpz_t uval, mpz_t val,
+	       source_location);
+
+  // Apply unary opcode OP to UVAL, setting VAL.  Return true if this
+  // could be done, false if not.
+  static bool
+  eval_float(Operator op, mpfr_t uval, mpfr_t val);
+
+  // Apply unary opcode OP to UREAL/UIMAG, setting REAL/IMAG.  Return
+  // true if this could be done, false if not.
+  static bool
+  eval_complex(Operator op, mpfr_t ureal, mpfr_t uimag, mpfr_t real,
+	       mpfr_t imag);
+
+  static Expression*
+  do_import(Import*);
+
+ protected:
+  int
+  do_traverse(Traverse* traverse)
+  { return Expression::traverse(&this->expr_, traverse); }
+
+  Expression*
+  do_lower(Gogo*, Named_object*, int);
+
+  bool
+  do_is_constant() const;
+
+  bool
+  do_integer_constant_value(bool, mpz_t, Type**) const;
+
+  bool
+  do_float_constant_value(mpfr_t, Type**) const;
+
+  bool
+  do_complex_constant_value(mpfr_t, mpfr_t, Type**) const;
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return Expression::make_unary(this->op_, this->expr_->copy(),
+				  this->location());
+  }
+
+  bool
+  do_is_addressable() const
+  { return this->op_ == OPERATOR_MULT; }
+
+  tree
+  do_get_tree(Translate_context*);
+
+  void
+  do_export(Export*) const;
+
+ private:
+  // The unary operator to apply.
+  Operator op_;
+  // Normally true.  False if this is an address expression which does
+  // not escape the current function.
+  bool escapes_;
+  // The operand.
+  Expression* expr_;
+};
+
+// If we are taking the address of a composite literal, and the
+// contents are not constant, then we want to make a heap composite
+// instead.
+
+Expression*
+Unary_expression::do_lower(Gogo*, Named_object*, int)
+{
+  source_location loc = this->location();
+  Operator op = this->op_;
+  Expression* expr = this->expr_;
+
+  if (op == OPERATOR_MULT && expr->is_type_expression())
+    return Expression::make_type(Type::make_pointer_type(expr->type()), loc);
+
+  // *&x simplifies to x.  *(*T)(unsafe.Pointer)(&x) does not require
+  // moving x to the heap.  FIXME: Is it worth doing a real escape
+  // analysis here?  This case is found in math/unsafe.go and is
+  // therefore worth special casing.
+  if (op == OPERATOR_MULT)
+    {
+      Expression* e = expr;
+      while (e->classification() == EXPRESSION_CONVERSION)
+	{
+	  Type_conversion_expression* te
+	    = static_cast<Type_conversion_expression*>(e);
+	  e = te->expr();
+	}
+
+      if (e->classification() == EXPRESSION_UNARY)
+	{
+	  Unary_expression* ue = static_cast<Unary_expression*>(e);
+	  if (ue->op_ == OPERATOR_AND)
+	    {
+	      if (e == expr)
+		{
+		  // *&x == x.
+		  return ue->expr_;
+		}
+	      ue->set_does_not_escape();
+	    }
+	}
+    }
+
+  if (op == OPERATOR_PLUS || op == OPERATOR_MINUS
+      || op == OPERATOR_NOT || op == OPERATOR_XOR)
+    {
+      Expression* ret = NULL;
+
+      mpz_t eval;
+      mpz_init(eval);
+      Type* etype;
+      if (expr->integer_constant_value(false, eval, &etype))
+	{
+	  mpz_t val;
+	  mpz_init(val);
+	  if (Unary_expression::eval_integer(op, etype, eval, val, loc))
+	    ret = Expression::make_integer(&val, etype, loc);
+	  mpz_clear(val);
+	}
+      mpz_clear(eval);
+      if (ret != NULL)
+	return ret;
+
+      if (op == OPERATOR_PLUS || op == OPERATOR_MINUS)
+	{
+	  mpfr_t fval;
+	  mpfr_init(fval);
+	  Type* ftype;
+	  if (expr->float_constant_value(fval, &ftype))
+	    {
+	      mpfr_t val;
+	      mpfr_init(val);
+	      if (Unary_expression::eval_float(op, fval, val))
+		ret = Expression::make_float(&val, ftype, loc);
+	      mpfr_clear(val);
+	    }
+	  if (ret != NULL)
+	    {
+	      mpfr_clear(fval);
+	      return ret;
+	    }
+
+	  mpfr_t ival;
+	  mpfr_init(ival);
+	  if (expr->complex_constant_value(fval, ival, &ftype))
+	    {
+	      mpfr_t real;
+	      mpfr_t imag;
+	      mpfr_init(real);
+	      mpfr_init(imag);
+	      if (Unary_expression::eval_complex(op, fval, ival, real, imag))
+		ret = Expression::make_complex(&real, &imag, ftype, loc);
+	      mpfr_clear(real);
+	      mpfr_clear(imag);
+	    }
+	  mpfr_clear(ival);
+	  mpfr_clear(fval);
+	  if (ret != NULL)
+	    return ret;
+	}
+    }
+
+  return this;
+}
+
+// Return whether a unary expression is a constant.
+
+bool
+Unary_expression::do_is_constant() const
+{
+  if (this->op_ == OPERATOR_MULT)
+    {
+      // Indirecting through a pointer is only constant if the object
+      // to which the expression points is constant, but we currently
+      // have no way to determine that.
+      return false;
+    }
+  else if (this->op_ == OPERATOR_AND)
+    {
+      // Taking the address of a variable is constant if it is a
+      // global variable, not constant otherwise.  In other cases
+      // taking the address is probably not a constant.
+      Var_expression* ve = this->expr_->var_expression();
+      if (ve != NULL)
+	{
+	  Named_object* no = ve->named_object();
+	  return no->is_variable() && no->var_value()->is_global();
+	}
+      return false;
+    }
+  else
+    return this->expr_->is_constant();
+}
+
+// Apply unary opcode OP to UVAL, setting VAL.  UTYPE is the type of
+// UVAL, if known; it may be NULL.  Return true if this could be done,
+// false if not.
+
+bool
+Unary_expression::eval_integer(Operator op, Type* utype, mpz_t uval, mpz_t val,
+			       source_location location)
+{
+  switch (op)
+    {
+    case OPERATOR_PLUS:
+      mpz_set(val, uval);
+      return true;
+    case OPERATOR_MINUS:
+      mpz_neg(val, uval);
+      return Integer_expression::check_constant(val, utype, location);
+    case OPERATOR_NOT:
+      mpz_set_ui(val, mpz_cmp_si(uval, 0) == 0 ? 1 : 0);
+      return true;
+    case OPERATOR_XOR:
+      if (utype == NULL
+	  || utype->integer_type() == NULL
+	  || utype->integer_type()->is_abstract())
+	mpz_com(val, uval);
+      else
+	{
+	  // The number of HOST_WIDE_INTs that it takes to represent
+	  // UVAL.
+	  size_t count = ((mpz_sizeinbase(uval, 2)
+			   + HOST_BITS_PER_WIDE_INT
+			   - 1)
+			  / HOST_BITS_PER_WIDE_INT);
+
+	  unsigned HOST_WIDE_INT* phwi = new unsigned HOST_WIDE_INT[count];
+	  memset(phwi, 0, count * sizeof(HOST_WIDE_INT));
+
+	  size_t ecount;
+	  mpz_export(phwi, &ecount, -1, sizeof(HOST_WIDE_INT), 0, 0, uval);
+	  gcc_assert(ecount <= count);
+
+	  // Trim down to the number of words required by the type.
+	  size_t obits = utype->integer_type()->bits();
+	  if (!utype->integer_type()->is_unsigned())
+	    ++obits;
+	  size_t ocount = ((obits + HOST_BITS_PER_WIDE_INT - 1)
+			   / HOST_BITS_PER_WIDE_INT);
+	  gcc_assert(ocount <= ocount);
+
+	  for (size_t i = 0; i < ocount; ++i)
+	    phwi[i] = ~phwi[i];
+
+	  size_t clearbits = ocount * HOST_BITS_PER_WIDE_INT - obits;
+	  if (clearbits != 0)
+	    phwi[ocount - 1] &= (((unsigned HOST_WIDE_INT) (HOST_WIDE_INT) -1)
+				 >> clearbits);
+
+	  mpz_import(val, ocount, -1, sizeof(HOST_WIDE_INT), 0, 0, phwi);
+
+	  delete[] phwi;
+	}
+      return Integer_expression::check_constant(val, utype, location);
+    case OPERATOR_AND:
+    case OPERATOR_MULT:
+      return false;
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Apply unary opcode OP to UVAL, setting VAL.  Return true if this
+// could be done, false if not.
+
+bool
+Unary_expression::eval_float(Operator op, mpfr_t uval, mpfr_t val)
+{
+  switch (op)
+    {
+    case OPERATOR_PLUS:
+      mpfr_set(val, uval, GMP_RNDN);
+      return true;
+    case OPERATOR_MINUS:
+      mpfr_neg(val, uval, GMP_RNDN);
+      return true;
+    case OPERATOR_NOT:
+    case OPERATOR_XOR:
+    case OPERATOR_AND:
+    case OPERATOR_MULT:
+      return false;
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Apply unary opcode OP to RVAL/IVAL, setting REAL/IMAG.  Return true
+// if this could be done, false if not.
+
+bool
+Unary_expression::eval_complex(Operator op, mpfr_t rval, mpfr_t ival,
+			       mpfr_t real, mpfr_t imag)
+{
+  switch (op)
+    {
+    case OPERATOR_PLUS:
+      mpfr_set(real, rval, GMP_RNDN);
+      mpfr_set(imag, ival, GMP_RNDN);
+      return true;
+    case OPERATOR_MINUS:
+      mpfr_neg(real, rval, GMP_RNDN);
+      mpfr_neg(imag, ival, GMP_RNDN);
+      return true;
+    case OPERATOR_NOT:
+    case OPERATOR_XOR:
+    case OPERATOR_AND:
+    case OPERATOR_MULT:
+      return false;
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Return the integral constant value of a unary expression, if it has one.
+
+bool
+Unary_expression::do_integer_constant_value(bool iota_is_constant, mpz_t val,
+					    Type** ptype) const
+{
+  mpz_t uval;
+  mpz_init(uval);
+  bool ret;
+  if (!this->expr_->integer_constant_value(iota_is_constant, uval, ptype))
+    ret = false;
+  else
+    ret = Unary_expression::eval_integer(this->op_, *ptype, uval, val,
+					 this->location());
+  mpz_clear(uval);
+  return ret;
+}
+
+// Return the floating point constant value of a unary expression, if
+// it has one.
+
+bool
+Unary_expression::do_float_constant_value(mpfr_t val, Type** ptype) const
+{
+  mpfr_t uval;
+  mpfr_init(uval);
+  bool ret;
+  if (!this->expr_->float_constant_value(uval, ptype))
+    ret = false;
+  else
+    ret = Unary_expression::eval_float(this->op_, uval, val);
+  mpfr_clear(uval);
+  return ret;
+}
+
+// Return the complex constant value of a unary expression, if it has
+// one.
+
+bool
+Unary_expression::do_complex_constant_value(mpfr_t real, mpfr_t imag,
+					    Type** ptype) const
+{
+  mpfr_t rval;
+  mpfr_t ival;
+  mpfr_init(rval);
+  mpfr_init(ival);
+  bool ret;
+  if (!this->expr_->complex_constant_value(rval, ival, ptype))
+    ret = false;
+  else
+    ret = Unary_expression::eval_complex(this->op_, rval, ival, real, imag);
+  mpfr_clear(rval);
+  mpfr_clear(ival);
+  return ret;
+}
+
+// Return the type of a unary expression.
+
+Type*
+Unary_expression::do_type()
+{
+  switch (this->op_)
+    {
+    case OPERATOR_PLUS:
+    case OPERATOR_MINUS:
+    case OPERATOR_NOT:
+    case OPERATOR_XOR:
+      return this->expr_->type();
+
+    case OPERATOR_AND:
+      return Type::make_pointer_type(this->expr_->type());
+
+    case OPERATOR_MULT:
+      {
+	Type* subtype = this->expr_->type();
+	Type* points_to = subtype->points_to();
+	if (points_to == NULL)
+	  return Type::make_error_type();
+	return points_to;
+      }
+
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Determine abstract types for a unary expression.
+
+void
+Unary_expression::do_determine_type(const Type_context* context)
+{
+  switch (this->op_)
+    {
+    case OPERATOR_PLUS:
+    case OPERATOR_MINUS:
+    case OPERATOR_NOT:
+    case OPERATOR_XOR:
+      this->expr_->determine_type(context);
+      break;
+
+    case OPERATOR_AND:
+      // Taking the address of something.
+      {
+	Type* subtype = (context->type == NULL
+			 ? NULL
+			 : context->type->points_to());
+	Type_context subcontext(subtype, false);
+	this->expr_->determine_type(&subcontext);
+      }
+      break;
+
+    case OPERATOR_MULT:
+      // Indirecting through a pointer.
+      {
+	Type* subtype = (context->type == NULL
+			 ? NULL
+			 : Type::make_pointer_type(context->type));
+	Type_context subcontext(subtype, false);
+	this->expr_->determine_type(&subcontext);
+      }
+      break;
+
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Check types for a unary expression.
+
+void
+Unary_expression::do_check_types(Gogo*)
+{
+  Type* type = this->expr_->type();
+  if (type->is_error_type())
+    {
+      this->set_is_error();
+      return;
+    }
+
+  switch (this->op_)
+    {
+    case OPERATOR_PLUS:
+    case OPERATOR_MINUS:
+      if (type->integer_type() == NULL
+	  && type->float_type() == NULL
+	  && type->complex_type() == NULL)
+	this->report_error(_("expected numeric type"));
+      break;
+
+    case OPERATOR_NOT:
+    case OPERATOR_XOR:
+      if (type->integer_type() == NULL
+	  && !type->is_boolean_type())
+	this->report_error(_("expected integer or boolean type"));
+      break;
+
+    case OPERATOR_AND:
+      if (!this->expr_->is_addressable())
+	this->report_error(_("invalid operand for unary %<&%>"));
+      else
+	this->expr_->address_taken(this->escapes_);
+      break;
+
+    case OPERATOR_MULT:
+      // Indirecting through a pointer.
+      if (type->points_to() == NULL)
+	this->report_error(_("expected pointer"));
+      break;
+
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Get a tree for a unary expression.
+
+tree
+Unary_expression::do_get_tree(Translate_context* context)
+{
+  tree expr = this->expr_->get_tree(context);
+  if (expr == error_mark_node)
+    return error_mark_node;
+
+  source_location loc = this->location();
+  switch (this->op_)
+    {
+    case OPERATOR_PLUS:
+      return expr;
+
+    case OPERATOR_MINUS:
+      {
+	tree type = TREE_TYPE(expr);
+	tree compute_type = excess_precision_type(type);
+	if (compute_type != NULL_TREE)
+	  expr = ::convert(compute_type, expr);
+	tree ret = fold_build1_loc(loc, NEGATE_EXPR,
+				   (compute_type != NULL_TREE
+				    ? compute_type
+				    : type),
+				   expr);
+	if (compute_type != NULL_TREE)
+	  ret = ::convert(type, ret);
+	return ret;
+      }
+
+    case OPERATOR_NOT:
+      if (TREE_CODE(TREE_TYPE(expr)) == BOOLEAN_TYPE)
+	return fold_build1_loc(loc, TRUTH_NOT_EXPR, TREE_TYPE(expr), expr);
+      else
+	return fold_build2_loc(loc, NE_EXPR, boolean_type_node, expr,
+			       build_int_cst(TREE_TYPE(expr), 0));
+
+    case OPERATOR_XOR:
+      return fold_build1_loc(loc, BIT_NOT_EXPR, TREE_TYPE(expr), expr);
+
+    case OPERATOR_AND:
+      // We should not see a non-constant constructor here; cases
+      // where we would see one should have been moved onto the heap
+      // at parse time.  Taking the address of a nonconstant
+      // constructor will not do what the programmer expects.
+      gcc_assert(TREE_CODE(expr) != CONSTRUCTOR || TREE_CONSTANT(expr));
+      gcc_assert(TREE_CODE(expr) != ADDR_EXPR);
+
+      // Build a decl for a constant constructor.
+      if (TREE_CODE(expr) == CONSTRUCTOR && TREE_CONSTANT(expr))
+	{
+	  tree decl = build_decl(this->location(), VAR_DECL,
+				 create_tmp_var_name("C"), TREE_TYPE(expr));
+	  DECL_EXTERNAL(decl) = 0;
+	  TREE_PUBLIC(decl) = 0;
+	  TREE_READONLY(decl) = 1;
+	  TREE_CONSTANT(decl) = 1;
+	  TREE_STATIC(decl) = 1;
+	  TREE_ADDRESSABLE(decl) = 1;
+	  DECL_ARTIFICIAL(decl) = 1;
+	  DECL_INITIAL(decl) = expr;
+	  rest_of_decl_compilation(decl, 1, 0);
+	  expr = decl;
+	}
+
+      return build_fold_addr_expr_loc(loc, expr);
+
+    case OPERATOR_MULT:
+      {
+	gcc_assert(POINTER_TYPE_P(TREE_TYPE(expr)));
+
+	// If we are dereferencing the pointer to a large struct, we
+	// need to check for nil.  We don't bother to check for small
+	// structs because we expect the system to crash on a nil
+	// pointer dereference.
+	HOST_WIDE_INT s = int_size_in_bytes(TREE_TYPE(TREE_TYPE(expr)));
+	if (s == -1 || s >= 4096)
+	  {
+	    if (!DECL_P(expr))
+	      expr = save_expr(expr);
+	    tree compare = fold_build2_loc(loc, EQ_EXPR, boolean_type_node,
+					   expr,
+					   fold_convert(TREE_TYPE(expr),
+							null_pointer_node));
+	    tree crash = Gogo::runtime_error(RUNTIME_ERROR_NIL_DEREFERENCE,
+					     loc);
+	    expr = fold_build2_loc(loc, COMPOUND_EXPR, TREE_TYPE(expr),
+				   build3(COND_EXPR, void_type_node,
+					  compare, crash, NULL_TREE),
+				   expr);
+	  }
+
+	// If the type of EXPR is a recursive pointer type, then we
+	// need to insert a cast before indirecting.
+	if (TREE_TYPE(TREE_TYPE(expr)) == ptr_type_node)
+	  {
+	    Type* pt = this->expr_->type()->points_to();
+	    tree ind = pt->get_tree(context->gogo());
+	    expr = fold_convert_loc(loc, build_pointer_type(ind), expr);
+	  }
+
+	return build_fold_indirect_ref_loc(loc, expr);
+      }
+
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Export a unary expression.
+
+void
+Unary_expression::do_export(Export* exp) const
+{
+  switch (this->op_)
+    {
+    case OPERATOR_PLUS:
+      exp->write_c_string("+ ");
+      break;
+    case OPERATOR_MINUS:
+      exp->write_c_string("- ");
+      break;
+    case OPERATOR_NOT:
+      exp->write_c_string("! ");
+      break;
+    case OPERATOR_XOR:
+      exp->write_c_string("^ ");
+      break;
+    case OPERATOR_AND:
+    case OPERATOR_MULT:
+    default:
+      gcc_unreachable();
+    }
+  this->expr_->export_expression(exp);
+}
+
+// Import a unary expression.
+
+Expression*
+Unary_expression::do_import(Import* imp)
+{
+  Operator op;
+  switch (imp->get_char())
+    {
+    case '+':
+      op = OPERATOR_PLUS;
+      break;
+    case '-':
+      op = OPERATOR_MINUS;
+      break;
+    case '!':
+      op = OPERATOR_NOT;
+      break;
+    case '^':
+      op = OPERATOR_XOR;
+      break;
+    default:
+      gcc_unreachable();
+    }
+  imp->require_c_string(" ");
+  Expression* expr = Expression::import_expression(imp);
+  return Expression::make_unary(op, expr, imp->location());
+}
+
+// Make a unary expression.
+
+Expression*
+Expression::make_unary(Operator op, Expression* expr, source_location location)
+{
+  return new Unary_expression(op, expr, location);
+}
+
+// If this is an indirection through a pointer, return the expression
+// being pointed through.  Otherwise return this.
+
+Expression*
+Expression::deref()
+{
+  if (this->classification_ == EXPRESSION_UNARY)
+    {
+      Unary_expression* ue = static_cast<Unary_expression*>(this);
+      if (ue->op() == OPERATOR_MULT)
+	return ue->operand();
+    }
+  return this;
+}
+
+// Class Binary_expression.
+
+// Traversal.
+
+int
+Binary_expression::do_traverse(Traverse* traverse)
+{
+  int t = Expression::traverse(&this->left_, traverse);
+  if (t == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return Expression::traverse(&this->right_, traverse);
+}
+
+// Compare integer constants according to OP.
+
+bool
+Binary_expression::compare_integer(Operator op, mpz_t left_val,
+				   mpz_t right_val)
+{
+  int i = mpz_cmp(left_val, right_val);
+  switch (op)
+    {
+    case OPERATOR_EQEQ:
+      return i == 0;
+    case OPERATOR_NOTEQ:
+      return i != 0;
+    case OPERATOR_LT:
+      return i < 0;
+    case OPERATOR_LE:
+      return i <= 0;
+    case OPERATOR_GT:
+      return i > 0;
+    case OPERATOR_GE:
+      return i >= 0;
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Compare floating point constants according to OP.
+
+bool
+Binary_expression::compare_float(Operator op, Type* type, mpfr_t left_val,
+				 mpfr_t right_val)
+{
+  int i;
+  if (type == NULL)
+    i = mpfr_cmp(left_val, right_val);
+  else
+    {
+      mpfr_t lv;
+      mpfr_init_set(lv, left_val, GMP_RNDN);
+      mpfr_t rv;
+      mpfr_init_set(rv, right_val, GMP_RNDN);
+      Float_expression::constrain_float(lv, type);
+      Float_expression::constrain_float(rv, type);
+      i = mpfr_cmp(lv, rv);
+      mpfr_clear(lv);
+      mpfr_clear(rv);
+    }
+  switch (op)
+    {
+    case OPERATOR_EQEQ:
+      return i == 0;
+    case OPERATOR_NOTEQ:
+      return i != 0;
+    case OPERATOR_LT:
+      return i < 0;
+    case OPERATOR_LE:
+      return i <= 0;
+    case OPERATOR_GT:
+      return i > 0;
+    case OPERATOR_GE:
+      return i >= 0;
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Compare complex constants according to OP.  Complex numbers may
+// only be compared for equality.
+
+bool
+Binary_expression::compare_complex(Operator op, Type* type,
+				   mpfr_t left_real, mpfr_t left_imag,
+				   mpfr_t right_real, mpfr_t right_imag)
+{
+  bool is_equal;
+  if (type == NULL)
+    is_equal = (mpfr_cmp(left_real, right_real) == 0
+		&& mpfr_cmp(left_imag, right_imag) == 0);
+  else
+    {
+      mpfr_t lr;
+      mpfr_t li;
+      mpfr_init_set(lr, left_real, GMP_RNDN);
+      mpfr_init_set(li, left_imag, GMP_RNDN);
+      mpfr_t rr;
+      mpfr_t ri;
+      mpfr_init_set(rr, right_real, GMP_RNDN);
+      mpfr_init_set(ri, right_imag, GMP_RNDN);
+      Complex_expression::constrain_complex(lr, li, type);
+      Complex_expression::constrain_complex(rr, ri, type);
+      is_equal = mpfr_cmp(lr, rr) == 0 && mpfr_cmp(li, ri) == 0;
+      mpfr_clear(lr);
+      mpfr_clear(li);
+      mpfr_clear(rr);
+      mpfr_clear(ri);
+    }
+  switch (op)
+    {
+    case OPERATOR_EQEQ:
+      return is_equal;
+    case OPERATOR_NOTEQ:
+      return !is_equal;
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Apply binary opcode OP to LEFT_VAL and RIGHT_VAL, setting VAL.
+// LEFT_TYPE is the type of LEFT_VAL, RIGHT_TYPE is the type of
+// RIGHT_VAL; LEFT_TYPE and/or RIGHT_TYPE may be NULL.  Return true if
+// this could be done, false if not.
+
+bool
+Binary_expression::eval_integer(Operator op, Type* left_type, mpz_t left_val,
+				Type* right_type, mpz_t right_val,
+				source_location location, mpz_t val)
+{
+  bool is_shift_op = false;
+  switch (op)
+    {
+    case OPERATOR_OROR:
+    case OPERATOR_ANDAND:
+    case OPERATOR_EQEQ:
+    case OPERATOR_NOTEQ:
+    case OPERATOR_LT:
+    case OPERATOR_LE:
+    case OPERATOR_GT:
+    case OPERATOR_GE:
+      // These return boolean values.  We should probably handle them
+      // anyhow in case a type conversion is used on the result.
+      return false;
+    case OPERATOR_PLUS:
+      mpz_add(val, left_val, right_val);
+      break;
+    case OPERATOR_MINUS:
+      mpz_sub(val, left_val, right_val);
+      break;
+    case OPERATOR_OR:
+      mpz_ior(val, left_val, right_val);
+      break;
+    case OPERATOR_XOR:
+      mpz_xor(val, left_val, right_val);
+      break;
+    case OPERATOR_MULT:
+      mpz_mul(val, left_val, right_val);
+      break;
+    case OPERATOR_DIV:
+      if (mpz_sgn(right_val) != 0)
+	mpz_tdiv_q(val, left_val, right_val);
+      else
+	{
+	  error_at(location, "division by zero");
+	  mpz_set_ui(val, 0);
+	  return true;
+	}
+      break;
+    case OPERATOR_MOD:
+      if (mpz_sgn(right_val) != 0)
+	mpz_tdiv_r(val, left_val, right_val);
+      else
+	{
+	  error_at(location, "division by zero");
+	  mpz_set_ui(val, 0);
+	  return true;
+	}
+      break;
+    case OPERATOR_LSHIFT:
+      {
+	unsigned long shift = mpz_get_ui(right_val);
+	if (mpz_cmp_ui(right_val, shift) != 0 || shift > 0x100000)
+	  {
+	    error_at(location, "shift count overflow");
+	    mpz_set_ui(val, 0);
+	    return true;
+	  }
+	mpz_mul_2exp(val, left_val, shift);
+	is_shift_op = true;
+	break;
+      }
+      break;
+    case OPERATOR_RSHIFT:
+      {
+	unsigned long shift = mpz_get_ui(right_val);
+	if (mpz_cmp_ui(right_val, shift) != 0)
+	  {
+	    error_at(location, "shift count overflow");
+	    mpz_set_ui(val, 0);
+	    return true;
+	  }
+	if (mpz_cmp_ui(left_val, 0) >= 0)
+	  mpz_tdiv_q_2exp(val, left_val, shift);
+	else
+	  mpz_fdiv_q_2exp(val, left_val, shift);
+	is_shift_op = true;
+	break;
+      }
+      break;
+    case OPERATOR_AND:
+      mpz_and(val, left_val, right_val);
+      break;
+    case OPERATOR_BITCLEAR:
+      {
+	mpz_t tval;
+	mpz_init(tval);
+	mpz_com(tval, right_val);
+	mpz_and(val, left_val, tval);
+	mpz_clear(tval);
+      }
+      break;
+    default:
+      gcc_unreachable();
+    }
+
+  Type* type = left_type;
+  if (!is_shift_op)
+    {
+      if (type == NULL)
+	type = right_type;
+      else if (type != right_type && right_type != NULL)
+	{
+	  if (type->is_abstract())
+	    type = right_type;
+	  else if (!right_type->is_abstract())
+	    {
+	      // This look like a type error which should be diagnosed
+	      // elsewhere.  Don't do anything here, to avoid an
+	      // unhelpful chain of error messages.
+	      return true;
+	    }
+	}
+    }
+
+  if (type != NULL && !type->is_abstract())
+    {
+      // We have to check the operands too, as we have implicitly
+      // coerced them to TYPE.
+      if ((type != left_type
+	   && !Integer_expression::check_constant(left_val, type, location))
+	  || (!is_shift_op
+	      && type != right_type
+	      && !Integer_expression::check_constant(right_val, type,
+						     location))
+	  || !Integer_expression::check_constant(val, type, location))
+	mpz_set_ui(val, 0);
+    }
+
+  return true;
+}
+
+// Apply binary opcode OP to LEFT_VAL and RIGHT_VAL, setting VAL.
+// Return true if this could be done, false if not.
+
+bool
+Binary_expression::eval_float(Operator op, Type* left_type, mpfr_t left_val,
+			      Type* right_type, mpfr_t right_val,
+			      mpfr_t val, source_location location)
+{
+  switch (op)
+    {
+    case OPERATOR_OROR:
+    case OPERATOR_ANDAND:
+    case OPERATOR_EQEQ:
+    case OPERATOR_NOTEQ:
+    case OPERATOR_LT:
+    case OPERATOR_LE:
+    case OPERATOR_GT:
+    case OPERATOR_GE:
+      // These return boolean values.  We should probably handle them
+      // anyhow in case a type conversion is used on the result.
+      return false;
+    case OPERATOR_PLUS:
+      mpfr_add(val, left_val, right_val, GMP_RNDN);
+      break;
+    case OPERATOR_MINUS:
+      mpfr_sub(val, left_val, right_val, GMP_RNDN);
+      break;
+    case OPERATOR_OR:
+    case OPERATOR_XOR:
+    case OPERATOR_AND:
+    case OPERATOR_BITCLEAR:
+      return false;
+    case OPERATOR_MULT:
+      mpfr_mul(val, left_val, right_val, GMP_RNDN);
+      break;
+    case OPERATOR_DIV:
+      if (mpfr_zero_p(right_val))
+	error_at(location, "division by zero");
+      mpfr_div(val, left_val, right_val, GMP_RNDN);
+      break;
+    case OPERATOR_MOD:
+      return false;
+    case OPERATOR_LSHIFT:
+    case OPERATOR_RSHIFT:
+      return false;
+    default:
+      gcc_unreachable();
+    }
+
+  Type* type = left_type;
+  if (type == NULL)
+    type = right_type;
+  else if (type != right_type && right_type != NULL)
+    {
+      if (type->is_abstract())
+	type = right_type;
+      else if (!right_type->is_abstract())
+	{
+	  // This looks like a type error which should be diagnosed
+	  // elsewhere.  Don't do anything here, to avoid an unhelpful
+	  // chain of error messages.
+	  return true;
+	}
+    }
+
+  if (type != NULL && !type->is_abstract())
+    {
+      if ((type != left_type
+	   && !Float_expression::check_constant(left_val, type, location))
+	  || (type != right_type
+	      && !Float_expression::check_constant(right_val, type,
+						   location))
+	  || !Float_expression::check_constant(val, type, location))
+	mpfr_set_ui(val, 0, GMP_RNDN);
+    }
+
+  return true;
+}
+
+// Apply binary opcode OP to LEFT_REAL/LEFT_IMAG and
+// RIGHT_REAL/RIGHT_IMAG, setting REAL/IMAG.  Return true if this
+// could be done, false if not.
+
+bool
+Binary_expression::eval_complex(Operator op, Type* left_type,
+				mpfr_t left_real, mpfr_t left_imag,
+				Type *right_type,
+				mpfr_t right_real, mpfr_t right_imag,
+				mpfr_t real, mpfr_t imag,
+				source_location location)
+{
+  switch (op)
+    {
+    case OPERATOR_OROR:
+    case OPERATOR_ANDAND:
+    case OPERATOR_EQEQ:
+    case OPERATOR_NOTEQ:
+    case OPERATOR_LT:
+    case OPERATOR_LE:
+    case OPERATOR_GT:
+    case OPERATOR_GE:
+      // These return boolean values and must be handled differently.
+      return false;
+    case OPERATOR_PLUS:
+      mpfr_add(real, left_real, right_real, GMP_RNDN);
+      mpfr_add(imag, left_imag, right_imag, GMP_RNDN);
+      break;
+    case OPERATOR_MINUS:
+      mpfr_sub(real, left_real, right_real, GMP_RNDN);
+      mpfr_sub(imag, left_imag, right_imag, GMP_RNDN);
+      break;
+    case OPERATOR_OR:
+    case OPERATOR_XOR:
+    case OPERATOR_AND:
+    case OPERATOR_BITCLEAR:
+      return false;
+    case OPERATOR_MULT:
+      {
+	// You might think that multiplying two complex numbers would
+	// be simple, and you would be right, until you start to think
+	// about getting the right answer for infinity.  If one
+	// operand here is infinity and the other is anything other
+	// than zero or NaN, then we are going to wind up subtracting
+	// two infinity values.  That will give us a NaN, but the
+	// correct answer is infinity.
+
+	mpfr_t lrrr;
+	mpfr_init(lrrr);
+	mpfr_mul(lrrr, left_real, right_real, GMP_RNDN);
+
+	mpfr_t lrri;
+	mpfr_init(lrri);
+	mpfr_mul(lrri, left_real, right_imag, GMP_RNDN);
+
+	mpfr_t lirr;
+	mpfr_init(lirr);
+	mpfr_mul(lirr, left_imag, right_real, GMP_RNDN);
+
+	mpfr_t liri;
+	mpfr_init(liri);
+	mpfr_mul(liri, left_imag, right_imag, GMP_RNDN);
+
+	mpfr_sub(real, lrrr, liri, GMP_RNDN);
+	mpfr_add(imag, lrri, lirr, GMP_RNDN);
+
+	// If we get NaN on both sides, check whether it should really
+	// be infinity.  The rule is that if either side of the
+	// complex number is infinity, then the whole value is
+	// infinity, even if the other side is NaN.  So the only case
+	// we have to fix is the one in which both sides are NaN.
+	if (mpfr_nan_p(real) && mpfr_nan_p(imag)
+	    && (!mpfr_nan_p(left_real) || !mpfr_nan_p(left_imag))
+	    && (!mpfr_nan_p(right_real) || !mpfr_nan_p(right_imag)))
+	  {
+	    bool is_infinity = false;
+
+	    mpfr_t lr;
+	    mpfr_t li;
+	    mpfr_init_set(lr, left_real, GMP_RNDN);
+	    mpfr_init_set(li, left_imag, GMP_RNDN);
+
+	    mpfr_t rr;
+	    mpfr_t ri;
+	    mpfr_init_set(rr, right_real, GMP_RNDN);
+	    mpfr_init_set(ri, right_imag, GMP_RNDN);
+
+	    // If the left side is infinity, then the result is
+	    // infinity.
+	    if (mpfr_inf_p(lr) || mpfr_inf_p(li))
+	      {
+		mpfr_set_ui(lr, mpfr_inf_p(lr) ? 1 : 0, GMP_RNDN);
+		mpfr_copysign(lr, lr, left_real, GMP_RNDN);
+		mpfr_set_ui(li, mpfr_inf_p(li) ? 1 : 0, GMP_RNDN);
+		mpfr_copysign(li, li, left_imag, GMP_RNDN);
+		if (mpfr_nan_p(rr))
+		  {
+		    mpfr_set_ui(rr, 0, GMP_RNDN);
+		    mpfr_copysign(rr, rr, right_real, GMP_RNDN);
+		  }
+		if (mpfr_nan_p(ri))
+		  {
+		    mpfr_set_ui(ri, 0, GMP_RNDN);
+		    mpfr_copysign(ri, ri, right_imag, GMP_RNDN);
+		  }
+		is_infinity = true;
+	      }
+
+	    // If the right side is infinity, then the result is
+	    // infinity.
+	    if (mpfr_inf_p(rr) || mpfr_inf_p(ri))
+	      {
+		mpfr_set_ui(rr, mpfr_inf_p(rr) ? 1 : 0, GMP_RNDN);
+		mpfr_copysign(rr, rr, right_real, GMP_RNDN);
+		mpfr_set_ui(ri, mpfr_inf_p(ri) ? 1 : 0, GMP_RNDN);
+		mpfr_copysign(ri, ri, right_imag, GMP_RNDN);
+		if (mpfr_nan_p(lr))
+		  {
+		    mpfr_set_ui(lr, 0, GMP_RNDN);
+		    mpfr_copysign(lr, lr, left_real, GMP_RNDN);
+		  }
+		if (mpfr_nan_p(li))
+		  {
+		    mpfr_set_ui(li, 0, GMP_RNDN);
+		    mpfr_copysign(li, li, left_imag, GMP_RNDN);
+		  }
+		is_infinity = true;
+	      }
+
+	    // If we got an overflow in the intermediate computations,
+	    // then the result is infinity.
+	    if (!is_infinity
+		&& (mpfr_inf_p(lrrr) || mpfr_inf_p(lrri)
+		    || mpfr_inf_p(lirr) || mpfr_inf_p(liri)))
+	      {
+		if (mpfr_nan_p(lr))
+		  {
+		    mpfr_set_ui(lr, 0, GMP_RNDN);
+		    mpfr_copysign(lr, lr, left_real, GMP_RNDN);
+		  }
+		if (mpfr_nan_p(li))
+		  {
+		    mpfr_set_ui(li, 0, GMP_RNDN);
+		    mpfr_copysign(li, li, left_imag, GMP_RNDN);
+		  }
+		if (mpfr_nan_p(rr))
+		  {
+		    mpfr_set_ui(rr, 0, GMP_RNDN);
+		    mpfr_copysign(rr, rr, right_real, GMP_RNDN);
+		  }
+		if (mpfr_nan_p(ri))
+		  {
+		    mpfr_set_ui(ri, 0, GMP_RNDN);
+		    mpfr_copysign(ri, ri, right_imag, GMP_RNDN);
+		  }
+		is_infinity = true;
+	      }
+
+	    if (is_infinity)
+	      {
+		mpfr_mul(lrrr, lr, rr, GMP_RNDN);
+		mpfr_mul(lrri, lr, ri, GMP_RNDN);
+		mpfr_mul(lirr, li, rr, GMP_RNDN);
+		mpfr_mul(liri, li, ri, GMP_RNDN);
+		mpfr_sub(real, lrrr, liri, GMP_RNDN);
+		mpfr_add(imag, lrri, lirr, GMP_RNDN);
+		mpfr_set_inf(real, mpfr_sgn(real));
+		mpfr_set_inf(imag, mpfr_sgn(imag));
+	      }
+
+	    mpfr_clear(lr);
+	    mpfr_clear(li);
+	    mpfr_clear(rr);
+	    mpfr_clear(ri);
+	  }
+
+	mpfr_clear(lrrr);
+	mpfr_clear(lrri);
+	mpfr_clear(lirr);
+	mpfr_clear(liri);				  
+      }
+      break;
+    case OPERATOR_DIV:
+      {
+	// For complex division we want to avoid having an
+	// intermediate overflow turn the whole result in a NaN.  We
+	// scale the values to try to avoid this.
+
+	if (mpfr_zero_p(right_real) && mpfr_zero_p(right_imag))
+	  error_at(location, "division by zero");
+
+	mpfr_t rra;
+	mpfr_t ria;
+	mpfr_init(rra);
+	mpfr_init(ria);
+	mpfr_abs(rra, right_real, GMP_RNDN);
+	mpfr_abs(ria, right_imag, GMP_RNDN);
+	mpfr_t t;
+	mpfr_init(t);
+	mpfr_max(t, rra, ria, GMP_RNDN);
+
+	mpfr_t rr;
+	mpfr_t ri;
+	mpfr_init_set(rr, right_real, GMP_RNDN);
+	mpfr_init_set(ri, right_imag, GMP_RNDN);
+	long ilogbw = 0;
+	if (!mpfr_inf_p(t) && !mpfr_nan_p(t) && !mpfr_zero_p(t))
+	  {
+	    ilogbw = mpfr_get_exp(t);
+	    mpfr_mul_2si(rr, rr, - ilogbw, GMP_RNDN);
+	    mpfr_mul_2si(ri, ri, - ilogbw, GMP_RNDN);
+	  }
+
+	mpfr_t denom;
+	mpfr_init(denom);
+	mpfr_mul(denom, rr, rr, GMP_RNDN);
+	mpfr_mul(t, ri, ri, GMP_RNDN);
+	mpfr_add(denom, denom, t, GMP_RNDN);
+
+	mpfr_mul(real, left_real, rr, GMP_RNDN);
+	mpfr_mul(t, left_imag, ri, GMP_RNDN);
+	mpfr_add(real, real, t, GMP_RNDN);
+	mpfr_div(real, real, denom, GMP_RNDN);
+	mpfr_mul_2si(real, real, - ilogbw, GMP_RNDN);
+
+	mpfr_mul(imag, left_imag, rr, GMP_RNDN);
+	mpfr_mul(t, left_real, ri, GMP_RNDN);
+	mpfr_sub(imag, imag, t, GMP_RNDN);
+	mpfr_div(imag, imag, denom, GMP_RNDN);
+	mpfr_mul_2si(imag, imag, - ilogbw, GMP_RNDN);
+
+	// If we wind up with NaN on both sides, check whether we
+	// should really have infinity.  The rule is that if either
+	// side of the complex number is infinity, then the whole
+	// value is infinity, even if the other side is NaN.  So the
+	// only case we have to fix is the one in which both sides are
+	// NaN.
+	if (mpfr_nan_p(real) && mpfr_nan_p(imag)
+	    && (!mpfr_nan_p(left_real) || !mpfr_nan_p(left_imag))
+	    && (!mpfr_nan_p(right_real) || !mpfr_nan_p(right_imag)))
+	  {
+	    if (mpfr_zero_p(denom))
+	      {
+		mpfr_set_inf(real, mpfr_sgn(rr));
+		mpfr_mul(real, real, left_real, GMP_RNDN);
+		mpfr_set_inf(imag, mpfr_sgn(rr));
+		mpfr_mul(imag, imag, left_imag, GMP_RNDN);
+	      }
+	    else if ((mpfr_inf_p(left_real) || mpfr_inf_p(left_imag))
+		     && mpfr_number_p(rr) && mpfr_number_p(ri))
+	      {
+		mpfr_set_ui(t, mpfr_inf_p(left_real) ? 1 : 0, GMP_RNDN);
+		mpfr_copysign(t, t, left_real, GMP_RNDN);
+
+		mpfr_t t2;
+		mpfr_init_set_ui(t2, mpfr_inf_p(left_imag) ? 1 : 0, GMP_RNDN);
+		mpfr_copysign(t2, t2, left_imag, GMP_RNDN);
+
+		mpfr_t t3;
+		mpfr_init(t3);
+		mpfr_mul(t3, t, rr, GMP_RNDN);
+
+		mpfr_t t4;
+		mpfr_init(t4);
+		mpfr_mul(t4, t2, ri, GMP_RNDN);
+
+		mpfr_add(t3, t3, t4, GMP_RNDN);
+		mpfr_set_inf(real, mpfr_sgn(t3));
+
+		mpfr_mul(t3, t2, rr, GMP_RNDN);
+		mpfr_mul(t4, t, ri, GMP_RNDN);
+		mpfr_sub(t3, t3, t4, GMP_RNDN);
+		mpfr_set_inf(imag, mpfr_sgn(t3));
+
+		mpfr_clear(t2);
+		mpfr_clear(t3);
+		mpfr_clear(t4);
+	      }
+	    else if ((mpfr_inf_p(right_real) || mpfr_inf_p(right_imag))
+		     && mpfr_number_p(left_real) && mpfr_number_p(left_imag))
+	      {
+		mpfr_set_ui(t, mpfr_inf_p(rr) ? 1 : 0, GMP_RNDN);
+		mpfr_copysign(t, t, rr, GMP_RNDN);
+
+		mpfr_t t2;
+		mpfr_init_set_ui(t2, mpfr_inf_p(ri) ? 1 : 0, GMP_RNDN);
+		mpfr_copysign(t2, t2, ri, GMP_RNDN);
+
+		mpfr_t t3;
+		mpfr_init(t3);
+		mpfr_mul(t3, left_real, t, GMP_RNDN);
+
+		mpfr_t t4;
+		mpfr_init(t4);
+		mpfr_mul(t4, left_imag, t2, GMP_RNDN);
+
+		mpfr_add(t3, t3, t4, GMP_RNDN);
+		mpfr_set_ui(real, 0, GMP_RNDN);
+		mpfr_mul(real, real, t3, GMP_RNDN);
+
+		mpfr_mul(t3, left_imag, t, GMP_RNDN);
+		mpfr_mul(t4, left_real, t2, GMP_RNDN);
+		mpfr_sub(t3, t3, t4, GMP_RNDN);
+		mpfr_set_ui(imag, 0, GMP_RNDN);
+		mpfr_mul(imag, imag, t3, GMP_RNDN);
+
+		mpfr_clear(t2);
+		mpfr_clear(t3);
+		mpfr_clear(t4);
+	      }
+	  }
+
+	mpfr_clear(denom);
+	mpfr_clear(rr);
+	mpfr_clear(ri);
+	mpfr_clear(t);
+	mpfr_clear(rra);
+	mpfr_clear(ria);
+      }
+      break;
+    case OPERATOR_MOD:
+      return false;
+    case OPERATOR_LSHIFT:
+    case OPERATOR_RSHIFT:
+      return false;
+    default:
+      gcc_unreachable();
+    }
+
+  Type* type = left_type;
+  if (type == NULL)
+    type = right_type;
+  else if (type != right_type && right_type != NULL)
+    {
+      if (type->is_abstract())
+	type = right_type;
+      else if (!right_type->is_abstract())
+	{
+	  // This looks like a type error which should be diagnosed
+	  // elsewhere.  Don't do anything here, to avoid an unhelpful
+	  // chain of error messages.
+	  return true;
+	}
+    }
+
+  if (type != NULL && !type->is_abstract())
+    {
+      if ((type != left_type
+	   && !Complex_expression::check_constant(left_real, left_imag,
+						  type, location))
+	  || (type != right_type
+	      && !Complex_expression::check_constant(right_real, right_imag,
+						     type, location))
+	  || !Complex_expression::check_constant(real, imag, type,
+						 location))
+	{
+	  mpfr_set_ui(real, 0, GMP_RNDN);
+	  mpfr_set_ui(imag, 0, GMP_RNDN);
+	}
+    }
+
+  return true;
+}
+
+// Lower a binary expression.  We have to evaluate constant
+// expressions now, in order to implement Go's unlimited precision
+// constants.
+
+Expression*
+Binary_expression::do_lower(Gogo*, Named_object*, int)
+{
+  source_location location = this->location();
+  Operator op = this->op_;
+  Expression* left = this->left_;
+  Expression* right = this->right_;
+
+  const bool is_comparison = (op == OPERATOR_EQEQ
+			      || op == OPERATOR_NOTEQ
+			      || op == OPERATOR_LT
+			      || op == OPERATOR_LE
+			      || op == OPERATOR_GT
+			      || op == OPERATOR_GE);
+
+  // Integer constant expressions.
+  {
+    mpz_t left_val;
+    mpz_init(left_val);
+    Type* left_type;
+    mpz_t right_val;
+    mpz_init(right_val);
+    Type* right_type;
+    if (left->integer_constant_value(false, left_val, &left_type)
+	&& right->integer_constant_value(false, right_val, &right_type))
+      {
+	Expression* ret = NULL;
+	if (left_type != right_type
+	    && left_type != NULL
+	    && right_type != NULL
+	    && left_type->base() != right_type->base()
+	    && op != OPERATOR_LSHIFT
+	    && op != OPERATOR_RSHIFT)
+	  {
+	    // May be a type error--let it be diagnosed later.
+	  }
+	else if (is_comparison)
+	  {
+	    bool b = Binary_expression::compare_integer(op, left_val,
+							right_val);
+	    ret = Expression::make_cast(Type::lookup_bool_type(),
+					Expression::make_boolean(b, location),
+					location);
+	  }
+	else
+	  {
+	    mpz_t val;
+	    mpz_init(val);
+
+	    if (Binary_expression::eval_integer(op, left_type, left_val,
+						right_type, right_val,
+						location, val))
+	      {
+		gcc_assert(op != OPERATOR_OROR && op != OPERATOR_ANDAND);
+		Type* type;
+		if (op == OPERATOR_LSHIFT || op == OPERATOR_RSHIFT)
+		  type = left_type;
+		else if (left_type == NULL)
+		  type = right_type;
+		else if (right_type == NULL)
+		  type = left_type;
+		else if (!left_type->is_abstract()
+			 && left_type->named_type() != NULL)
+		  type = left_type;
+		else if (!right_type->is_abstract()
+			 && right_type->named_type() != NULL)
+		  type = right_type;
+		else if (!left_type->is_abstract())
+		  type = left_type;
+		else if (!right_type->is_abstract())
+		  type = right_type;
+		else if (left_type->float_type() != NULL)
+		  type = left_type;
+		else if (right_type->float_type() != NULL)
+		  type = right_type;
+		else if (left_type->complex_type() != NULL)
+		  type = left_type;
+		else if (right_type->complex_type() != NULL)
+		  type = right_type;
+		else
+		  type = left_type;
+		ret = Expression::make_integer(&val, type, location);
+	      }
+
+	    mpz_clear(val);
+	  }
+
+	if (ret != NULL)
+	  {
+	    mpz_clear(right_val);
+	    mpz_clear(left_val);
+	    return ret;
+	  }
+      }
+    mpz_clear(right_val);
+    mpz_clear(left_val);
+  }
+
+  // Floating point constant expressions.
+  {
+    mpfr_t left_val;
+    mpfr_init(left_val);
+    Type* left_type;
+    mpfr_t right_val;
+    mpfr_init(right_val);
+    Type* right_type;
+    if (left->float_constant_value(left_val, &left_type)
+	&& right->float_constant_value(right_val, &right_type))
+      {
+	Expression* ret = NULL;
+	if (left_type != right_type
+	    && left_type != NULL
+	    && right_type != NULL
+	    && left_type->base() != right_type->base()
+	    && op != OPERATOR_LSHIFT
+	    && op != OPERATOR_RSHIFT)
+	  {
+	    // May be a type error--let it be diagnosed later.
+	  }
+	else if (is_comparison)
+	  {
+	    bool b = Binary_expression::compare_float(op,
+						      (left_type != NULL
+						       ? left_type
+						       : right_type),
+						      left_val, right_val);
+	    ret = Expression::make_boolean(b, location);
+	  }
+	else
+	  {
+	    mpfr_t val;
+	    mpfr_init(val);
+
+	    if (Binary_expression::eval_float(op, left_type, left_val,
+					      right_type, right_val, val,
+					      location))
+	      {
+		gcc_assert(op != OPERATOR_OROR && op != OPERATOR_ANDAND
+			   && op != OPERATOR_LSHIFT && op != OPERATOR_RSHIFT);
+		Type* type;
+		if (left_type == NULL)
+		  type = right_type;
+		else if (right_type == NULL)
+		  type = left_type;
+		else if (!left_type->is_abstract()
+			 && left_type->named_type() != NULL)
+		  type = left_type;
+		else if (!right_type->is_abstract()
+			 && right_type->named_type() != NULL)
+		  type = right_type;
+		else if (!left_type->is_abstract())
+		  type = left_type;
+		else if (!right_type->is_abstract())
+		  type = right_type;
+		else if (left_type->float_type() != NULL)
+		  type = left_type;
+		else if (right_type->float_type() != NULL)
+		  type = right_type;
+		else
+		  type = left_type;
+		ret = Expression::make_float(&val, type, location);
+	      }
+
+	    mpfr_clear(val);
+	  }
+
+	if (ret != NULL)
+	  {
+	    mpfr_clear(right_val);
+	    mpfr_clear(left_val);
+	    return ret;
+	  }
+      }
+    mpfr_clear(right_val);
+    mpfr_clear(left_val);
+  }
+
+  // Complex constant expressions.
+  {
+    mpfr_t left_real;
+    mpfr_t left_imag;
+    mpfr_init(left_real);
+    mpfr_init(left_imag);
+    Type* left_type;
+
+    mpfr_t right_real;
+    mpfr_t right_imag;
+    mpfr_init(right_real);
+    mpfr_init(right_imag);
+    Type* right_type;
+
+    if (left->complex_constant_value(left_real, left_imag, &left_type)
+	&& right->complex_constant_value(right_real, right_imag, &right_type))
+      {
+	Expression* ret = NULL;
+	if (left_type != right_type
+	    && left_type != NULL
+	    && right_type != NULL
+	    && left_type->base() != right_type->base())
+	  {
+	    // May be a type error--let it be diagnosed later.
+	  }
+	else if (op == OPERATOR_EQEQ || op == OPERATOR_NOTEQ)
+	  {
+	    bool b = Binary_expression::compare_complex(op,
+							(left_type != NULL
+							 ? left_type
+							 : right_type),
+							left_real,
+							left_imag,
+							right_real,
+							right_imag);
+	    ret = Expression::make_boolean(b, location);
+	  }
+	else
+	  {
+	    mpfr_t real;
+	    mpfr_t imag;
+	    mpfr_init(real);
+	    mpfr_init(imag);
+
+	    if (Binary_expression::eval_complex(op, left_type,
+						left_real, left_imag,
+						right_type,
+						right_real, right_imag,
+						real, imag,
+						location))
+	      {
+		gcc_assert(op != OPERATOR_OROR && op != OPERATOR_ANDAND
+			   && op != OPERATOR_LSHIFT && op != OPERATOR_RSHIFT);
+		Type* type;
+		if (left_type == NULL)
+		  type = right_type;
+		else if (right_type == NULL)
+		  type = left_type;
+		else if (!left_type->is_abstract()
+			 && left_type->named_type() != NULL)
+		  type = left_type;
+		else if (!right_type->is_abstract()
+			 && right_type->named_type() != NULL)
+		  type = right_type;
+		else if (!left_type->is_abstract())
+		  type = left_type;
+		else if (!right_type->is_abstract())
+		  type = right_type;
+		else if (left_type->complex_type() != NULL)
+		  type = left_type;
+		else if (right_type->complex_type() != NULL)
+		  type = right_type;
+		else
+		  type = left_type;
+		ret = Expression::make_complex(&real, &imag, type,
+					       location);
+	      }
+	    mpfr_clear(real);
+	    mpfr_clear(imag);
+	  }
+
+	if (ret != NULL)
+	  {
+	    mpfr_clear(left_real);
+	    mpfr_clear(left_imag);
+	    mpfr_clear(right_real);
+	    mpfr_clear(right_imag);
+	    return ret;
+	  }
+      }
+
+    mpfr_clear(left_real);
+    mpfr_clear(left_imag);
+    mpfr_clear(right_real);
+    mpfr_clear(right_imag);
+  }
+
+  // String constant expressions.
+  if (op == OPERATOR_PLUS
+      && left->type()->is_string_type()
+      && right->type()->is_string_type())
+    {
+      std::string left_string;
+      std::string right_string;
+      if (left->string_constant_value(&left_string)
+	  && right->string_constant_value(&right_string))
+	return Expression::make_string(left_string + right_string, location);
+    }
+
+  return this;
+}
+
+// Return the integer constant value, if it has one.
+
+bool
+Binary_expression::do_integer_constant_value(bool iota_is_constant, mpz_t val,
+					     Type** ptype) const
+{
+  mpz_t left_val;
+  mpz_init(left_val);
+  Type* left_type;
+  if (!this->left_->integer_constant_value(iota_is_constant, left_val,
+					   &left_type))
+    {
+      mpz_clear(left_val);
+      return false;
+    }
+
+  mpz_t right_val;
+  mpz_init(right_val);
+  Type* right_type;
+  if (!this->right_->integer_constant_value(iota_is_constant, right_val,
+					    &right_type))
+    {
+      mpz_clear(right_val);
+      mpz_clear(left_val);
+      return false;
+    }
+
+  bool ret;
+  if (left_type != right_type
+      && left_type != NULL
+      && right_type != NULL
+      && left_type->base() != right_type->base()
+      && this->op_ != OPERATOR_RSHIFT
+      && this->op_ != OPERATOR_LSHIFT)
+    ret = false;
+  else
+    ret = Binary_expression::eval_integer(this->op_, left_type, left_val,
+					  right_type, right_val,
+					  this->location(), val);
+
+  mpz_clear(right_val);
+  mpz_clear(left_val);
+
+  if (ret)
+    *ptype = left_type;
+
+  return ret;
+}
+
+// Return the floating point constant value, if it has one.
+
+bool
+Binary_expression::do_float_constant_value(mpfr_t val, Type** ptype) const
+{
+  mpfr_t left_val;
+  mpfr_init(left_val);
+  Type* left_type;
+  if (!this->left_->float_constant_value(left_val, &left_type))
+    {
+      mpfr_clear(left_val);
+      return false;
+    }
+
+  mpfr_t right_val;
+  mpfr_init(right_val);
+  Type* right_type;
+  if (!this->right_->float_constant_value(right_val, &right_type))
+    {
+      mpfr_clear(right_val);
+      mpfr_clear(left_val);
+      return false;
+    }
+
+  bool ret;
+  if (left_type != right_type
+      && left_type != NULL
+      && right_type != NULL
+      && left_type->base() != right_type->base())
+    ret = false;
+  else
+    ret = Binary_expression::eval_float(this->op_, left_type, left_val,
+					right_type, right_val,
+					val, this->location());
+
+  mpfr_clear(left_val);
+  mpfr_clear(right_val);
+
+  if (ret)
+    *ptype = left_type;
+
+  return ret;
+}
+
+// Return the complex constant value, if it has one.
+
+bool
+Binary_expression::do_complex_constant_value(mpfr_t real, mpfr_t imag,
+					     Type** ptype) const
+{
+  mpfr_t left_real;
+  mpfr_t left_imag;
+  mpfr_init(left_real);
+  mpfr_init(left_imag);
+  Type* left_type;
+  if (!this->left_->complex_constant_value(left_real, left_imag, &left_type))
+    {
+      mpfr_clear(left_real);
+      mpfr_clear(left_imag);
+      return false;
+    }
+
+  mpfr_t right_real;
+  mpfr_t right_imag;
+  mpfr_init(right_real);
+  mpfr_init(right_imag);
+  Type* right_type;
+  if (!this->right_->complex_constant_value(right_real, right_imag,
+					    &right_type))
+    {
+      mpfr_clear(left_real);
+      mpfr_clear(left_imag);
+      mpfr_clear(right_real);
+      mpfr_clear(right_imag);
+      return false;
+    }
+
+  bool ret;
+  if (left_type != right_type
+      && left_type != NULL
+      && right_type != NULL
+      && left_type->base() != right_type->base())
+    ret = false;
+  else
+    ret = Binary_expression::eval_complex(this->op_, left_type,
+					  left_real, left_imag,
+					  right_type,
+					  right_real, right_imag,
+					  real, imag,
+					  this->location());
+  mpfr_clear(left_real);
+  mpfr_clear(left_imag);
+  mpfr_clear(right_real);
+  mpfr_clear(right_imag);
+
+  if (ret)
+    *ptype = left_type;
+
+  return ret;
+}
+
+// Note that the value is being discarded.
+
+void
+Binary_expression::do_discarding_value()
+{
+  if (this->op_ == OPERATOR_OROR || this->op_ == OPERATOR_ANDAND)
+    this->right_->discarding_value();
+  else
+    this->warn_about_unused_value();
+}
+
+// Get type.
+
+Type*
+Binary_expression::do_type()
+{
+  if (this->classification() == EXPRESSION_ERROR)
+    return Type::make_error_type();
+
+  switch (this->op_)
+    {
+    case OPERATOR_OROR:
+    case OPERATOR_ANDAND:
+    case OPERATOR_EQEQ:
+    case OPERATOR_NOTEQ:
+    case OPERATOR_LT:
+    case OPERATOR_LE:
+    case OPERATOR_GT:
+    case OPERATOR_GE:
+      return Type::lookup_bool_type();
+
+    case OPERATOR_PLUS:
+    case OPERATOR_MINUS:
+    case OPERATOR_OR:
+    case OPERATOR_XOR:
+    case OPERATOR_MULT:
+    case OPERATOR_DIV:
+    case OPERATOR_MOD:
+    case OPERATOR_AND:
+    case OPERATOR_BITCLEAR:
+      {
+	Type* left_type = this->left_->type();
+	Type* right_type = this->right_->type();
+	if (left_type->is_error_type())
+	  return left_type;
+	else if (right_type->is_error_type())
+	  return right_type;
+	else if (!Type::are_compatible_for_binop(left_type, right_type))
+	  {
+	    this->report_error(_("incompatible types in binary expression"));
+	    return Type::make_error_type();
+	  }
+	else if (!left_type->is_abstract() && left_type->named_type() != NULL)
+	  return left_type;
+	else if (!right_type->is_abstract() && right_type->named_type() != NULL)
+	  return right_type;
+	else if (!left_type->is_abstract())
+	  return left_type;
+	else if (!right_type->is_abstract())
+	  return right_type;
+	else if (left_type->complex_type() != NULL)
+	  return left_type;
+	else if (right_type->complex_type() != NULL)
+	  return right_type;
+	else if (left_type->float_type() != NULL)
+	  return left_type;
+	else if (right_type->float_type() != NULL)
+	  return right_type;
+	else
+	  return left_type;
+      }
+
+    case OPERATOR_LSHIFT:
+    case OPERATOR_RSHIFT:
+      return this->left_->type();
+
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Set type for a binary expression.
+
+void
+Binary_expression::do_determine_type(const Type_context* context)
+{
+  Type* tleft = this->left_->type();
+  Type* tright = this->right_->type();
+
+  // Both sides should have the same type, except for the shift
+  // operations.  For a comparison, we should ignore the incoming
+  // type.
+
+  bool is_shift_op = (this->op_ == OPERATOR_LSHIFT
+		      || this->op_ == OPERATOR_RSHIFT);
+
+  bool is_comparison = (this->op_ == OPERATOR_EQEQ
+			|| this->op_ == OPERATOR_NOTEQ
+			|| this->op_ == OPERATOR_LT
+			|| this->op_ == OPERATOR_LE
+			|| this->op_ == OPERATOR_GT
+			|| this->op_ == OPERATOR_GE);
+
+  Type_context subcontext(*context);
+
+  if (is_comparison)
+    {
+      // In a comparison, the context does not determine the types of
+      // the operands.
+      subcontext.type = NULL;
+    }
+
+  // Set the context for the left hand operand.
+  if (is_shift_op)
+    {
+      // The right hand operand plays no role in determining the type
+      // of the left hand operand.  A shift of an abstract integer in
+      // a string context gets special treatment, which may be a
+      // language bug.
+      if (subcontext.type != NULL
+	  && subcontext.type->is_string_type()
+	  && tleft->is_abstract())
+	error_at(this->location(), "shift of non-integer operand");
+    }
+  else if (!tleft->is_abstract())
+    subcontext.type = tleft;
+  else if (!tright->is_abstract())
+    subcontext.type = tright;
+  else if (subcontext.type == NULL)
+    {
+      if ((tleft->integer_type() != NULL && tright->integer_type() != NULL)
+	  || (tleft->float_type() != NULL && tright->float_type() != NULL)
+	  || (tleft->complex_type() != NULL && tright->complex_type() != NULL))
+	{
+	  // Both sides have an abstract integer, abstract float, or
+	  // abstract complex type.  Just let CONTEXT determine
+	  // whether they may remain abstract or not.
+	}
+      else if (tleft->complex_type() != NULL)
+	subcontext.type = tleft;
+      else if (tright->complex_type() != NULL)
+	subcontext.type = tright;
+      else if (tleft->float_type() != NULL)
+	subcontext.type = tleft;
+      else if (tright->float_type() != NULL)
+	subcontext.type = tright;
+      else
+	subcontext.type = tleft;
+
+      if (subcontext.type != NULL && !context->may_be_abstract)
+	subcontext.type = subcontext.type->make_non_abstract_type();
+    }
+
+  this->left_->determine_type(&subcontext);
+
+  // The context for the right hand operand is the same as for the
+  // left hand operand, except for a shift operator.
+  if (is_shift_op)
+    {
+      subcontext.type = Type::lookup_integer_type("uint");
+      subcontext.may_be_abstract = false;
+    }
+
+  this->right_->determine_type(&subcontext);
+}
+
+// Report an error if the binary operator OP does not support TYPE.
+// Return whether the operation is OK.  This should not be used for
+// shift.
+
+bool
+Binary_expression::check_operator_type(Operator op, Type* type,
+				       source_location location)
+{
+  switch (op)
+    {
+    case OPERATOR_OROR:
+    case OPERATOR_ANDAND:
+      if (!type->is_boolean_type())
+	{
+	  error_at(location, "expected boolean type");
+	  return false;
+	}
+      break;
+
+    case OPERATOR_EQEQ:
+    case OPERATOR_NOTEQ:
+      if (type->integer_type() == NULL
+	  && type->float_type() == NULL
+	  && type->complex_type() == NULL
+	  && !type->is_string_type()
+	  && type->points_to() == NULL
+	  && !type->is_nil_type()
+	  && !type->is_boolean_type()
+	  && type->interface_type() == NULL
+	  && (type->array_type() == NULL
+	      || type->array_type()->length() != NULL)
+	  && type->map_type() == NULL
+	  && type->channel_type() == NULL
+	  && type->function_type() == NULL)
+	{
+	  error_at(location,
+		   ("expected integer, floating, complex, string, pointer, "
+		    "boolean, interface, slice, map, channel, "
+		    "or function type"));
+	  return false;
+	}
+      break;
+
+    case OPERATOR_LT:
+    case OPERATOR_LE:
+    case OPERATOR_GT:
+    case OPERATOR_GE:
+      if (type->integer_type() == NULL
+	  && type->float_type() == NULL
+	  && !type->is_string_type())
+	{
+	  error_at(location, "expected integer, floating, or string type");
+	  return false;
+	}
+      break;
+
+    case OPERATOR_PLUS:
+    case OPERATOR_PLUSEQ:
+      if (type->integer_type() == NULL
+	  && type->float_type() == NULL
+	  && type->complex_type() == NULL
+	  && !type->is_string_type())
+	{
+	  error_at(location,
+		   "expected integer, floating, complex, or string type");
+	  return false;
+	}
+      break;
+
+    case OPERATOR_MINUS:
+    case OPERATOR_MINUSEQ:
+    case OPERATOR_MULT:
+    case OPERATOR_MULTEQ:
+    case OPERATOR_DIV:
+    case OPERATOR_DIVEQ:
+      if (type->integer_type() == NULL
+	  && type->float_type() == NULL
+	  && type->complex_type() == NULL)
+	{
+	  error_at(location, "expected integer, floating, or complex type");
+	  return false;
+	}
+      break;
+
+    case OPERATOR_MOD:
+    case OPERATOR_MODEQ:
+    case OPERATOR_OR:
+    case OPERATOR_OREQ:
+    case OPERATOR_AND:
+    case OPERATOR_ANDEQ:
+    case OPERATOR_XOR:
+    case OPERATOR_XOREQ:
+    case OPERATOR_BITCLEAR:
+    case OPERATOR_BITCLEAREQ:
+      if (type->integer_type() == NULL)
+	{
+	  error_at(location, "expected integer type");
+	  return false;
+	}
+      break;
+
+    default:
+      gcc_unreachable();
+    }
+
+  return true;
+}
+
+// Check types.
+
+void
+Binary_expression::do_check_types(Gogo*)
+{
+  if (this->classification() == EXPRESSION_ERROR)
+    return;
+
+  Type* left_type = this->left_->type();
+  Type* right_type = this->right_->type();
+  if (left_type->is_error_type() || right_type->is_error_type())
+    {
+      this->set_is_error();
+      return;
+    }
+
+  if (this->op_ == OPERATOR_EQEQ
+      || this->op_ == OPERATOR_NOTEQ
+      || this->op_ == OPERATOR_LT
+      || this->op_ == OPERATOR_LE
+      || this->op_ == OPERATOR_GT
+      || this->op_ == OPERATOR_GE)
+    {
+      if (!Type::are_assignable(left_type, right_type, NULL)
+	  && !Type::are_assignable(right_type, left_type, NULL))
+	{
+	  this->report_error(_("incompatible types in binary expression"));
+	  return;
+	}
+      if (!Binary_expression::check_operator_type(this->op_, left_type,
+						  this->location())
+	  || !Binary_expression::check_operator_type(this->op_, right_type,
+						     this->location()))
+	{
+	  this->set_is_error();
+	  return;
+	}
+    }
+  else if (this->op_ != OPERATOR_LSHIFT && this->op_ != OPERATOR_RSHIFT)
+    {
+      if (!Type::are_compatible_for_binop(left_type, right_type))
+	{
+	  this->report_error(_("incompatible types in binary expression"));
+	  return;
+	}
+      if (!Binary_expression::check_operator_type(this->op_, left_type,
+						  this->location()))
+	{
+	  this->set_is_error();
+	  return;
+	}
+    }
+  else
+    {
+      if (left_type->integer_type() == NULL)
+	this->report_error(_("shift of non-integer operand"));
+
+      if (!right_type->is_abstract()
+	  && (right_type->integer_type() == NULL
+	      || !right_type->integer_type()->is_unsigned()))
+	this->report_error(_("shift count not unsigned integer"));
+      else
+	{
+	  mpz_t val;
+	  mpz_init(val);
+	  Type* type;
+	  if (this->right_->integer_constant_value(true, val, &type))
+	    {
+	      if (mpz_sgn(val) < 0)
+		this->report_error(_("negative shift count"));
+	    }
+	  mpz_clear(val);
+	}
+    }
+}
+
+// Get a tree for a binary expression.
+
+tree
+Binary_expression::do_get_tree(Translate_context* context)
+{
+  tree left = this->left_->get_tree(context);
+  tree right = this->right_->get_tree(context);
+
+  if (left == error_mark_node || right == error_mark_node)
+    return error_mark_node;
+
+  enum tree_code code;
+  bool use_left_type = true;
+  bool is_shift_op = false;
+  switch (this->op_)
+    {
+    case OPERATOR_EQEQ:
+    case OPERATOR_NOTEQ:
+    case OPERATOR_LT:
+    case OPERATOR_LE:
+    case OPERATOR_GT:
+    case OPERATOR_GE:
+      return Expression::comparison_tree(context, this->op_,
+					 this->left_->type(), left,
+					 this->right_->type(), right,
+					 this->location());
+
+    case OPERATOR_OROR:
+      code = TRUTH_ORIF_EXPR;
+      use_left_type = false;
+      break;
+    case OPERATOR_ANDAND:
+      code = TRUTH_ANDIF_EXPR;
+      use_left_type = false;
+      break;
+    case OPERATOR_PLUS:
+      code = PLUS_EXPR;
+      break;
+    case OPERATOR_MINUS:
+      code = MINUS_EXPR;
+      break;
+    case OPERATOR_OR:
+      code = BIT_IOR_EXPR;
+      break;
+    case OPERATOR_XOR:
+      code = BIT_XOR_EXPR;
+      break;
+    case OPERATOR_MULT:
+      code = MULT_EXPR;
+      break;
+    case OPERATOR_DIV:
+      {
+	Type *t = this->left_->type();
+	if (t->float_type() != NULL || t->complex_type() != NULL)
+	  code = RDIV_EXPR;
+	else
+	  code = TRUNC_DIV_EXPR;
+      }
+      break;
+    case OPERATOR_MOD:
+      code = TRUNC_MOD_EXPR;
+      break;
+    case OPERATOR_LSHIFT:
+      code = LSHIFT_EXPR;
+      is_shift_op = true;
+      break;
+    case OPERATOR_RSHIFT:
+      code = RSHIFT_EXPR;
+      is_shift_op = true;
+      break;
+    case OPERATOR_AND:
+      code = BIT_AND_EXPR;
+      break;
+    case OPERATOR_BITCLEAR:
+      right = fold_build1(BIT_NOT_EXPR, TREE_TYPE(right), right);
+      code = BIT_AND_EXPR;
+      break;
+    default:
+      gcc_unreachable();
+    }
+
+  tree type = use_left_type ? TREE_TYPE(left) : TREE_TYPE(right);
+
+  if (this->left_->type()->is_string_type())
+    {
+      gcc_assert(this->op_ == OPERATOR_PLUS);
+      tree string_type = Type::make_string_type()->get_tree(context->gogo());
+      static tree string_plus_decl;
+      return Gogo::call_builtin(&string_plus_decl,
+				this->location(),
+				"__go_string_plus",
+				2,
+				string_type,
+				string_type,
+				left,
+				string_type,
+				right);
+    }
+
+  tree compute_type = excess_precision_type(type);
+  if (compute_type != NULL_TREE)
+    {
+      left = ::convert(compute_type, left);
+      right = ::convert(compute_type, right);
+    }
+
+  tree eval_saved = NULL_TREE;
+  if (is_shift_op)
+    {
+      // Make sure the values are evaluated.
+      if (!DECL_P(left) && TREE_SIDE_EFFECTS(left))
+	{
+	  left = save_expr(left);
+	  eval_saved = left;
+	}
+      if (!DECL_P(right) && TREE_SIDE_EFFECTS(right))
+	{
+	  right = save_expr(right);
+	  if (eval_saved == NULL_TREE)
+	    eval_saved = right;
+	  else
+	    eval_saved = fold_build2_loc(this->location(), COMPOUND_EXPR,
+					 void_type_node, eval_saved, right);
+	}
+    }
+
+  tree ret = fold_build2_loc(this->location(),
+			     code,
+			     compute_type != NULL_TREE ? compute_type : type,
+			     left, right);
+
+  if (compute_type != NULL_TREE)
+    ret = ::convert(type, ret);
+
+  // In Go, a shift larger than the size of the type is well-defined.
+  // This is not true in GENERIC, so we need to insert a conditional.
+  if (is_shift_op)
+    {
+      gcc_assert(INTEGRAL_TYPE_P(TREE_TYPE(left)));
+      gcc_assert(this->left_->type()->integer_type() != NULL);
+      int bits = TYPE_PRECISION(TREE_TYPE(left));
+
+      tree compare = fold_build2(LT_EXPR, boolean_type_node, right,
+				 build_int_cst_type(TREE_TYPE(right), bits));
+
+      tree overflow_result = fold_convert_loc(this->location(),
+					      TREE_TYPE(left),
+					      integer_zero_node);
+      if (this->op_ == OPERATOR_RSHIFT
+	  && !this->left_->type()->integer_type()->is_unsigned())
+	{
+	  tree neg = fold_build2_loc(this->location(), LT_EXPR,
+				     boolean_type_node, left,
+				     fold_convert_loc(this->location(),
+						      TREE_TYPE(left),
+						      integer_zero_node));
+	  tree neg_one = fold_build2_loc(this->location(),
+					 MINUS_EXPR, TREE_TYPE(left),
+					 fold_convert_loc(this->location(),
+							  TREE_TYPE(left),
+							  integer_zero_node),
+					 fold_convert_loc(this->location(),
+							  TREE_TYPE(left),
+							  integer_one_node));
+	  overflow_result = fold_build3_loc(this->location(), COND_EXPR,
+					    TREE_TYPE(left), neg, neg_one,
+					    overflow_result);
+	}
+
+      ret = fold_build3_loc(this->location(), COND_EXPR, TREE_TYPE(left),
+			    compare, ret, overflow_result);
+
+      if (eval_saved != NULL_TREE)
+	ret = fold_build2_loc(this->location(), COMPOUND_EXPR,
+			      TREE_TYPE(ret), eval_saved, ret);
+    }
+
+  return ret;
+}
+
+// Export a binary expression.
+
+void
+Binary_expression::do_export(Export* exp) const
+{
+  exp->write_c_string("(");
+  this->left_->export_expression(exp);
+  switch (this->op_)
+    {
+    case OPERATOR_OROR:
+      exp->write_c_string(" || ");
+      break;
+    case OPERATOR_ANDAND:
+      exp->write_c_string(" && ");
+      break;
+    case OPERATOR_EQEQ:
+      exp->write_c_string(" == ");
+      break;
+    case OPERATOR_NOTEQ:
+      exp->write_c_string(" != ");
+      break;
+    case OPERATOR_LT:
+      exp->write_c_string(" < ");
+      break;
+    case OPERATOR_LE:
+      exp->write_c_string(" <= ");
+      break;
+    case OPERATOR_GT:
+      exp->write_c_string(" > ");
+      break;
+    case OPERATOR_GE:
+      exp->write_c_string(" >= ");
+      break;
+    case OPERATOR_PLUS:
+      exp->write_c_string(" + ");
+      break;
+    case OPERATOR_MINUS:
+      exp->write_c_string(" - ");
+      break;
+    case OPERATOR_OR:
+      exp->write_c_string(" | ");
+      break;
+    case OPERATOR_XOR:
+      exp->write_c_string(" ^ ");
+      break;
+    case OPERATOR_MULT:
+      exp->write_c_string(" * ");
+      break;
+    case OPERATOR_DIV:
+      exp->write_c_string(" / ");
+      break;
+    case OPERATOR_MOD:
+      exp->write_c_string(" % ");
+      break;
+    case OPERATOR_LSHIFT:
+      exp->write_c_string(" << ");
+      break;
+    case OPERATOR_RSHIFT:
+      exp->write_c_string(" >> ");
+      break;
+    case OPERATOR_AND:
+      exp->write_c_string(" & ");
+      break;
+    case OPERATOR_BITCLEAR:
+      exp->write_c_string(" &^ ");
+      break;
+    default:
+      gcc_unreachable();
+    }
+  this->right_->export_expression(exp);
+  exp->write_c_string(")");
+}
+
+// Import a binary expression.
+
+Expression*
+Binary_expression::do_import(Import* imp)
+{
+  imp->require_c_string("(");
+
+  Expression* left = Expression::import_expression(imp);
+
+  Operator op;
+  if (imp->match_c_string(" || "))
+    {
+      op = OPERATOR_OROR;
+      imp->advance(4);
+    }
+  else if (imp->match_c_string(" && "))
+    {
+      op = OPERATOR_ANDAND;
+      imp->advance(4);
+    }
+  else if (imp->match_c_string(" == "))
+    {
+      op = OPERATOR_EQEQ;
+      imp->advance(4);
+    }
+  else if (imp->match_c_string(" != "))
+    {
+      op = OPERATOR_NOTEQ;
+      imp->advance(4);
+    }
+  else if (imp->match_c_string(" < "))
+    {
+      op = OPERATOR_LT;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" <= "))
+    {
+      op = OPERATOR_LE;
+      imp->advance(4);
+    }
+  else if (imp->match_c_string(" > "))
+    {
+      op = OPERATOR_GT;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" >= "))
+    {
+      op = OPERATOR_GE;
+      imp->advance(4);
+    }
+  else if (imp->match_c_string(" + "))
+    {
+      op = OPERATOR_PLUS;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" - "))
+    {
+      op = OPERATOR_MINUS;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" | "))
+    {
+      op = OPERATOR_OR;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" ^ "))
+    {
+      op = OPERATOR_XOR;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" * "))
+    {
+      op = OPERATOR_MULT;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" / "))
+    {
+      op = OPERATOR_DIV;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" % "))
+    {
+      op = OPERATOR_MOD;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" << "))
+    {
+      op = OPERATOR_LSHIFT;
+      imp->advance(4);
+    }
+  else if (imp->match_c_string(" >> "))
+    {
+      op = OPERATOR_RSHIFT;
+      imp->advance(4);
+    }
+  else if (imp->match_c_string(" & "))
+    {
+      op = OPERATOR_AND;
+      imp->advance(3);
+    }
+  else if (imp->match_c_string(" &^ "))
+    {
+      op = OPERATOR_BITCLEAR;
+      imp->advance(4);
+    }
+  else
+    {
+      error_at(imp->location(), "unrecognized binary operator");
+      return Expression::make_error(imp->location());
+    }
+
+  Expression* right = Expression::import_expression(imp);
+
+  imp->require_c_string(")");
+
+  return Expression::make_binary(op, left, right, imp->location());
+}
+
+// Make a binary expression.
+
+Expression*
+Expression::make_binary(Operator op, Expression* left, Expression* right,
+			source_location location)
+{
+  return new Binary_expression(op, left, right, location);
+}
+
+// Implement a comparison.
+
+tree
+Expression::comparison_tree(Translate_context* context, Operator op,
+			    Type* left_type, tree left_tree,
+			    Type* right_type, tree right_tree,
+			    source_location location)
+{
+  enum tree_code code;
+  switch (op)
+    {
+    case OPERATOR_EQEQ:
+      code = EQ_EXPR;
+      break;
+    case OPERATOR_NOTEQ:
+      code = NE_EXPR;
+      break;
+    case OPERATOR_LT:
+      code = LT_EXPR;
+      break;
+    case OPERATOR_LE:
+      code = LE_EXPR;
+      break;
+    case OPERATOR_GT:
+      code = GT_EXPR;
+      break;
+    case OPERATOR_GE:
+      code = GE_EXPR;
+      break;
+    default:
+      gcc_unreachable();
+    }
+
+  if (left_type->is_string_type() && right_type->is_string_type())
+    {
+      tree string_type = Type::make_string_type()->get_tree(context->gogo());
+      static tree string_compare_decl;
+      left_tree = Gogo::call_builtin(&string_compare_decl,
+				     location,
+				     "__go_strcmp",
+				     2,
+				     integer_type_node,
+				     string_type,
+				     left_tree,
+				     string_type,
+				     right_tree);
+      right_tree = build_int_cst_type(integer_type_node, 0);
+    }
+  else if ((left_type->interface_type() != NULL
+	    && right_type->interface_type() == NULL
+	    && !right_type->is_nil_type())
+	   || (left_type->interface_type() == NULL
+	       && !left_type->is_nil_type()
+	       && right_type->interface_type() != NULL))
+    {
+      // Comparing an interface value to a non-interface value.
+      if (left_type->interface_type() == NULL)
+	{
+	  std::swap(left_type, right_type);
+	  std::swap(left_tree, right_tree);
+	}
+
+      // The right operand is not an interface.  We need to take its
+      // address if it is not a pointer.
+      tree make_tmp;
+      tree arg;
+      if (right_type->points_to() != NULL)
+	{
+	  make_tmp = NULL_TREE;
+	  arg = right_tree;
+	}
+      else if (TREE_ADDRESSABLE(TREE_TYPE(right_tree)) || DECL_P(right_tree))
+	{
+	  make_tmp = NULL_TREE;
+	  arg = build_fold_addr_expr_loc(location, right_tree);
+	  if (DECL_P(right_tree))
+	    TREE_ADDRESSABLE(right_tree) = 1;
+	}
+      else
+	{
+	  tree tmp = create_tmp_var(TREE_TYPE(right_tree),
+				    get_name(right_tree));
+	  DECL_IGNORED_P(tmp) = 0;
+	  DECL_INITIAL(tmp) = right_tree;
+	  TREE_ADDRESSABLE(tmp) = 1;
+	  make_tmp = build1(DECL_EXPR, void_type_node, tmp);
+	  SET_EXPR_LOCATION(make_tmp, location);
+	  arg = build_fold_addr_expr_loc(location, tmp);
+	}
+      arg = fold_convert_loc(location, ptr_type_node, arg);
+
+      tree descriptor = right_type->type_descriptor_pointer(context->gogo());
+
+      if (left_type->interface_type()->is_empty())
+	{
+	  static tree empty_interface_value_compare_decl;
+	  left_tree = Gogo::call_builtin(&empty_interface_value_compare_decl,
+					 location,
+					 "__go_empty_interface_value_compare",
+					 3,
+					 integer_type_node,
+					 TREE_TYPE(left_tree),
+					 left_tree,
+					 TREE_TYPE(descriptor),
+					 descriptor,
+					 ptr_type_node,
+					 arg);
+	  if (left_tree == error_mark_node)
+	    return error_mark_node;
+	  // This can panic if the type is not comparable.
+	  TREE_NOTHROW(empty_interface_value_compare_decl) = 0;
+	}
+      else
+	{
+	  static tree interface_value_compare_decl;
+	  left_tree = Gogo::call_builtin(&interface_value_compare_decl,
+					 location,
+					 "__go_interface_value_compare",
+					 3,
+					 integer_type_node,
+					 TREE_TYPE(left_tree),
+					 left_tree,
+					 TREE_TYPE(descriptor),
+					 descriptor,
+					 ptr_type_node,
+					 arg);
+	  if (left_tree == error_mark_node)
+	    return error_mark_node;
+	  // This can panic if the type is not comparable.
+	  TREE_NOTHROW(interface_value_compare_decl) = 0;
+	}
+      right_tree = build_int_cst_type(integer_type_node, 0);
+
+      if (make_tmp != NULL_TREE)
+	left_tree = build2(COMPOUND_EXPR, TREE_TYPE(left_tree), make_tmp,
+			   left_tree);
+    }
+  else if (left_type->interface_type() != NULL
+	   && right_type->interface_type() != NULL)
+    {
+      if (left_type->interface_type()->is_empty()
+	  && right_type->interface_type()->is_empty())
+	{
+	  static tree empty_interface_compare_decl;
+	  left_tree = Gogo::call_builtin(&empty_interface_compare_decl,
+					 location,
+					 "__go_empty_interface_compare",
+					 2,
+					 integer_type_node,
+					 TREE_TYPE(left_tree),
+					 left_tree,
+					 TREE_TYPE(right_tree),
+					 right_tree);
+	  if (left_tree == error_mark_node)
+	    return error_mark_node;
+	  // This can panic if the type is uncomparable.
+	  TREE_NOTHROW(empty_interface_compare_decl) = 0;
+	}
+      else if (!left_type->interface_type()->is_empty()
+	       && !right_type->interface_type()->is_empty())
+	{
+	  static tree interface_compare_decl;
+	  left_tree = Gogo::call_builtin(&interface_compare_decl,
+					 location,
+					 "__go_interface_compare",
+					 2,
+					 integer_type_node,
+					 TREE_TYPE(left_tree),
+					 left_tree,
+					 TREE_TYPE(right_tree),
+					 right_tree);
+	  if (left_tree == error_mark_node)
+	    return error_mark_node;
+	  // This can panic if the type is uncomparable.
+	  TREE_NOTHROW(interface_compare_decl) = 0;
+	}
+      else
+	{
+	  if (left_type->interface_type()->is_empty())
+	    {
+	      gcc_assert(op == OPERATOR_EQEQ || op == OPERATOR_NOTEQ);
+	      std::swap(left_type, right_type);
+	      std::swap(left_tree, right_tree);
+	    }
+	  gcc_assert(!left_type->interface_type()->is_empty());
+	  gcc_assert(right_type->interface_type()->is_empty());
+	  static tree interface_empty_compare_decl;
+	  left_tree = Gogo::call_builtin(&interface_empty_compare_decl,
+					 location,
+					 "__go_interface_empty_compare",
+					 2,
+					 integer_type_node,
+					 TREE_TYPE(left_tree),
+					 left_tree,
+					 TREE_TYPE(right_tree),
+					 right_tree);
+	  if (left_tree == error_mark_node)
+	    return error_mark_node;
+	  // This can panic if the type is uncomparable.
+	  TREE_NOTHROW(interface_empty_compare_decl) = 0;
+	}
+
+      right_tree = build_int_cst_type(integer_type_node, 0);
+    }
+
+  if (left_type->is_nil_type()
+      && (op == OPERATOR_EQEQ || op == OPERATOR_NOTEQ))
+    {
+      std::swap(left_type, right_type);
+      std::swap(left_tree, right_tree);
+    }
+
+  if (right_type->is_nil_type())
+    {
+      if (left_type->array_type() != NULL
+	  && left_type->array_type()->length() == NULL)
+	{
+	  Array_type* at = left_type->array_type();
+	  left_tree = at->value_pointer_tree(context->gogo(), left_tree);
+	  right_tree = fold_convert(TREE_TYPE(left_tree), null_pointer_node);
+	}
+      else if (left_type->interface_type() != NULL)
+	{
+	  // An interface is nil if the first field is nil.
+	  tree left_type_tree = TREE_TYPE(left_tree);
+	  gcc_assert(TREE_CODE(left_type_tree) == RECORD_TYPE);
+	  tree field = TYPE_FIELDS(left_type_tree);
+	  left_tree = build3(COMPONENT_REF, TREE_TYPE(field), left_tree,
+			     field, NULL_TREE);
+	  right_tree = fold_convert(TREE_TYPE(left_tree), null_pointer_node);
+	}
+      else
+	{
+	  gcc_assert(POINTER_TYPE_P(TREE_TYPE(left_tree)));
+	  right_tree = fold_convert(TREE_TYPE(left_tree), null_pointer_node);
+	}
+    }
+
+  if (left_tree == error_mark_node || right_tree == error_mark_node)
+    return error_mark_node;
+
+  tree ret = fold_build2(code, boolean_type_node, left_tree, right_tree);
+  if (CAN_HAVE_LOCATION_P(ret))
+    SET_EXPR_LOCATION(ret, location);
+  return ret;
+}
+
+// Class Bound_method_expression.
+
+// Traversal.
+
+int
+Bound_method_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->expr_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return Expression::traverse(&this->method_, traverse);
+}
+
+// Return the type of a bound method expression.  The type of this
+// object is really the type of the method with no receiver.  We
+// should be able to get away with just returning the type of the
+// method.
+
+Type*
+Bound_method_expression::do_type()
+{
+  return this->method_->type();
+}
+
+// Determine the types of a method expression.
+
+void
+Bound_method_expression::do_determine_type(const Type_context*)
+{
+  this->method_->determine_type_no_context();
+  Type* mtype = this->method_->type();
+  Function_type* fntype = mtype == NULL ? NULL : mtype->function_type();
+  if (fntype == NULL || !fntype->is_method())
+    this->expr_->determine_type_no_context();
+  else
+    {
+      Type_context subcontext(fntype->receiver()->type(), false);
+      this->expr_->determine_type(&subcontext);
+    }
+}
+
+// Check the types of a method expression.
+
+void
+Bound_method_expression::do_check_types(Gogo*)
+{
+  Type* type = this->method_->type()->deref();
+  if (type == NULL
+      || type->function_type() == NULL
+      || !type->function_type()->is_method())
+    this->report_error(_("object is not a method"));
+  else
+    {
+      Type* rtype = type->function_type()->receiver()->type()->deref();
+      Type* etype = (this->expr_type_ != NULL
+		     ? this->expr_type_
+		     : this->expr_->type());
+      etype = etype->deref();
+      if (!Type::are_identical(rtype, etype, true, NULL))
+	this->report_error(_("method type does not match object type"));
+    }
+}
+
+// Get the tree for a method expression.  There is no standard tree
+// representation for this.  The only places it may currently be used
+// are in a Call_expression or a Go_statement, which will take it
+// apart directly.  So this has nothing to do at present.
+
+tree
+Bound_method_expression::do_get_tree(Translate_context*)
+{
+  error_at(this->location(), "reference to method other than calling it");
+  return error_mark_node;
+}
+
+// Make a method expression.
+
+Bound_method_expression*
+Expression::make_bound_method(Expression* expr, Expression* method,
+			      source_location location)
+{
+  return new Bound_method_expression(expr, method, location);
+}
+
+// Class Builtin_call_expression.  This is used for a call to a
+// builtin function.
+
+class Builtin_call_expression : public Call_expression
+{
+ public:
+  Builtin_call_expression(Gogo* gogo, Expression* fn, Expression_list* args,
+			  bool is_varargs, source_location location);
+
+ protected:
+  // This overrides Call_expression::do_lower.
+  Expression*
+  do_lower(Gogo*, Named_object*, int);
+
+  bool
+  do_is_constant() const;
+
+  bool
+  do_integer_constant_value(bool, mpz_t, Type**) const;
+
+  bool
+  do_float_constant_value(mpfr_t, Type**) const;
+
+  bool
+  do_complex_constant_value(mpfr_t, mpfr_t, Type**) const;
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return new Builtin_call_expression(this->gogo_, this->fn()->copy(),
+				       this->args()->copy(),
+				       this->is_varargs(),
+				       this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context*);
+
+  void
+  do_export(Export*) const;
+
+  virtual bool
+  do_is_recover_call() const;
+
+  virtual void
+  do_set_recover_arg(Expression*);
+
+ private:
+  // The builtin functions.
+  enum Builtin_function_code
+    {
+      BUILTIN_INVALID,
+
+      // Predeclared builtin functions.
+      BUILTIN_APPEND,
+      BUILTIN_CAP,
+      BUILTIN_CLOSE,
+      BUILTIN_CLOSED,
+      BUILTIN_COMPLEX,
+      BUILTIN_COPY,
+      BUILTIN_IMAG,
+      BUILTIN_LEN,
+      BUILTIN_MAKE,
+      BUILTIN_NEW,
+      BUILTIN_PANIC,
+      BUILTIN_PRINT,
+      BUILTIN_PRINTLN,
+      BUILTIN_REAL,
+      BUILTIN_RECOVER,
+
+      // Builtin functions from the unsafe package.
+      BUILTIN_ALIGNOF,
+      BUILTIN_OFFSETOF,
+      BUILTIN_SIZEOF
+    };
+
+  Expression*
+  one_arg() const;
+
+  bool
+  check_one_arg();
+
+  static Type*
+  real_imag_type(Type*);
+
+  static Type*
+  complex_type(Type*);
+
+  // A pointer back to the general IR structure.  This avoids a global
+  // variable, or passing it around everywhere.
+  Gogo* gogo_;
+  // The builtin function being called.
+  Builtin_function_code code_;
+  // Used to stop endless loops when the length of an array uses len
+  // or cap of the array itself.
+  mutable bool seen_;
+};
+
+Builtin_call_expression::Builtin_call_expression(Gogo* gogo,
+						 Expression* fn,
+						 Expression_list* args,
+						 bool is_varargs,
+						 source_location location)
+  : Call_expression(fn, args, is_varargs, location),
+    gogo_(gogo), code_(BUILTIN_INVALID), seen_(false)
+{
+  Func_expression* fnexp = this->fn()->func_expression();
+  gcc_assert(fnexp != NULL);
+  const std::string& name(fnexp->named_object()->name());
+  if (name == "append")
+    this->code_ = BUILTIN_APPEND;
+  else if (name == "cap")
+    this->code_ = BUILTIN_CAP;
+  else if (name == "close")
+    this->code_ = BUILTIN_CLOSE;
+  else if (name == "closed")
+    this->code_ = BUILTIN_CLOSED;
+  else if (name == "complex")
+    this->code_ = BUILTIN_COMPLEX;
+  else if (name == "copy")
+    this->code_ = BUILTIN_COPY;
+  else if (name == "imag")
+    this->code_ = BUILTIN_IMAG;
+  else if (name == "len")
+    this->code_ = BUILTIN_LEN;
+  else if (name == "make")
+    this->code_ = BUILTIN_MAKE;
+  else if (name == "new")
+    this->code_ = BUILTIN_NEW;
+  else if (name == "panic")
+    this->code_ = BUILTIN_PANIC;
+  else if (name == "print")
+    this->code_ = BUILTIN_PRINT;
+  else if (name == "println")
+    this->code_ = BUILTIN_PRINTLN;
+  else if (name == "real")
+    this->code_ = BUILTIN_REAL;
+  else if (name == "recover")
+    this->code_ = BUILTIN_RECOVER;
+  else if (name == "Alignof")
+    this->code_ = BUILTIN_ALIGNOF;
+  else if (name == "Offsetof")
+    this->code_ = BUILTIN_OFFSETOF;
+  else if (name == "Sizeof")
+    this->code_ = BUILTIN_SIZEOF;
+  else
+    gcc_unreachable();
+}
+
+// Return whether this is a call to recover.  This is a virtual
+// function called from the parent class.
+
+bool
+Builtin_call_expression::do_is_recover_call() const
+{
+  if (this->classification() == EXPRESSION_ERROR)
+    return false;
+  return this->code_ == BUILTIN_RECOVER;
+}
+
+// Set the argument for a call to recover.
+
+void
+Builtin_call_expression::do_set_recover_arg(Expression* arg)
+{
+  const Expression_list* args = this->args();
+  gcc_assert(args == NULL || args->empty());
+  Expression_list* new_args = new Expression_list();
+  new_args->push_back(arg);
+  this->set_args(new_args);
+}
+
+// A traversal class which looks for a call expression.
+
+class Find_call_expression : public Traverse
+{
+ public:
+  Find_call_expression()
+    : Traverse(traverse_expressions),
+      found_(false)
+  { }
+
+  int
+  expression(Expression**);
+
+  bool
+  found()
+  { return this->found_; }
+
+ private:
+  bool found_;
+};
+
+int
+Find_call_expression::expression(Expression** pexpr)
+{
+  if ((*pexpr)->call_expression() != NULL)
+    {
+      this->found_ = true;
+      return TRAVERSE_EXIT;
+    }
+  return TRAVERSE_CONTINUE;
+}
+
+// Lower a builtin call expression.  This turns new and make into
+// specific expressions.  We also convert to a constant if we can.
+
+Expression*
+Builtin_call_expression::do_lower(Gogo* gogo, Named_object* function, int)
+{
+  if (this->code_ == BUILTIN_NEW)
+    {
+      const Expression_list* args = this->args();
+      if (args == NULL || args->size() < 1)
+	this->report_error(_("not enough arguments"));
+      else if (args->size() > 1)
+	this->report_error(_("too many arguments"));
+      else
+	{
+	  Expression* arg = args->front();
+	  if (!arg->is_type_expression())
+	    {
+	      error_at(arg->location(), "expected type");
+	      this->set_is_error();
+	    }
+	  else
+	    return Expression::make_allocation(arg->type(), this->location());
+	}
+    }
+  else if (this->code_ == BUILTIN_MAKE)
+    {
+      const Expression_list* args = this->args();
+      if (args == NULL || args->size() < 1)
+	this->report_error(_("not enough arguments"));
+      else
+	{
+	  Expression* arg = args->front();
+	  if (!arg->is_type_expression())
+	    {
+	      error_at(arg->location(), "expected type");
+	      this->set_is_error();
+	    }
+	  else
+	    {
+	      Expression_list* newargs;
+	      if (args->size() == 1)
+		newargs = NULL;
+	      else
+		{
+		  newargs = new Expression_list();
+		  Expression_list::const_iterator p = args->begin();
+		  ++p;
+		  for (; p != args->end(); ++p)
+		    newargs->push_back(*p);
+		}
+	      return Expression::make_make(arg->type(), newargs,
+					   this->location());
+	    }
+	}
+    }
+  else if (this->is_constant())
+    {
+      // We can only lower len and cap if there are no function calls
+      // in the arguments.  Otherwise we have to make the call.
+      if (this->code_ == BUILTIN_LEN || this->code_ == BUILTIN_CAP)
+	{
+	  Expression* arg = this->one_arg();
+	  if (!arg->is_constant())
+	    {
+	      Find_call_expression find_call;
+	      Expression::traverse(&arg, &find_call);
+	      if (find_call.found())
+		return this;
+	    }
+	}
+
+      mpz_t ival;
+      mpz_init(ival);
+      Type* type;
+      if (this->integer_constant_value(true, ival, &type))
+	{
+	  Expression* ret = Expression::make_integer(&ival, type,
+						     this->location());
+	  mpz_clear(ival);
+	  return ret;
+	}
+      mpz_clear(ival);
+
+      mpfr_t rval;
+      mpfr_init(rval);
+      if (this->float_constant_value(rval, &type))
+	{
+	  Expression* ret = Expression::make_float(&rval, type,
+						   this->location());
+	  mpfr_clear(rval);
+	  return ret;
+	}
+
+      mpfr_t imag;
+      mpfr_init(imag);
+      if (this->complex_constant_value(rval, imag, &type))
+	{
+	  Expression* ret = Expression::make_complex(&rval, &imag, type,
+						     this->location());
+	  mpfr_clear(rval);
+	  mpfr_clear(imag);
+	  return ret;
+	}
+      mpfr_clear(rval);
+      mpfr_clear(imag);
+    }
+  else if (this->code_ == BUILTIN_RECOVER)
+    {
+      if (function != NULL)
+	function->func_value()->set_calls_recover();
+      else
+	{
+	  // Calling recover outside of a function always returns the
+	  // nil empty interface.
+	  Type* eface = Type::make_interface_type(NULL, this->location());
+	  return Expression::make_cast(eface,
+				       Expression::make_nil(this->location()),
+				       this->location());
+	}
+    }
+  else if (this->code_ == BUILTIN_APPEND)
+    {
+      // Lower the varargs.
+      const Expression_list* args = this->args();
+      if (args == NULL || args->empty())
+	return this;
+      Type* slice_type = args->front()->type();
+      if (!slice_type->is_open_array_type())
+	{
+	  error_at(args->front()->location(), "argument 1 must be a slice");
+	  this->set_is_error();
+	  return this;
+	}
+      return this->lower_varargs(gogo, function, slice_type, 2);
+    }
+
+  return this;
+}
+
+// Return the type of the real or imag functions, given the type of
+// the argument.  We need to map complex to float, complex64 to
+// float32, and complex128 to float64, so it has to be done by name.
+// This returns NULL if it can't figure out the type.
+
+Type*
+Builtin_call_expression::real_imag_type(Type* arg_type)
+{
+  if (arg_type == NULL || arg_type->is_abstract())
+    return NULL;
+  Named_type* nt = arg_type->named_type();
+  if (nt == NULL)
+    return NULL;
+  while (nt->real_type()->named_type() != NULL)
+    nt = nt->real_type()->named_type();
+  if (nt->name() == "complex64")
+    return Type::lookup_float_type("float32");
+  else if (nt->name() == "complex128")
+    return Type::lookup_float_type("float64");
+  else
+    return NULL;
+}
+
+// Return the type of the complex function, given the type of one of the
+// argments.  Like real_imag_type, we have to map by name.
+
+Type*
+Builtin_call_expression::complex_type(Type* arg_type)
+{
+  if (arg_type == NULL || arg_type->is_abstract())
+    return NULL;
+  Named_type* nt = arg_type->named_type();
+  if (nt == NULL)
+    return NULL;
+  while (nt->real_type()->named_type() != NULL)
+    nt = nt->real_type()->named_type();
+  if (nt->name() == "float32")
+    return Type::lookup_complex_type("complex64");
+  else if (nt->name() == "float64")
+    return Type::lookup_complex_type("complex128");
+  else
+    return NULL;
+}
+
+// Return a single argument, or NULL if there isn't one.
+
+Expression*
+Builtin_call_expression::one_arg() const
+{
+  const Expression_list* args = this->args();
+  if (args->size() != 1)
+    return NULL;
+  return args->front();
+}
+
+// Return whether this is constant: len of a string, or len or cap of
+// a fixed array, or unsafe.Sizeof, unsafe.Offsetof, unsafe.Alignof.
+
+bool
+Builtin_call_expression::do_is_constant() const
+{
+  switch (this->code_)
+    {
+    case BUILTIN_LEN:
+    case BUILTIN_CAP:
+      {
+	if (this->seen_)
+	  return false;
+
+	Expression* arg = this->one_arg();
+	if (arg == NULL)
+	  return false;
+	Type* arg_type = arg->type();
+
+	if (arg_type->points_to() != NULL
+	    && arg_type->points_to()->array_type() != NULL
+	    && !arg_type->points_to()->is_open_array_type())
+	  arg_type = arg_type->points_to();
+
+	if (arg_type->array_type() != NULL
+	    && arg_type->array_type()->length() != NULL)
+	  return true;
+
+	if (this->code_ == BUILTIN_LEN && arg_type->is_string_type())
+	  {
+	    this->seen_ = true;
+	    bool ret = arg->is_constant();
+	    this->seen_ = false;
+	    return ret;
+	  }
+      }
+      break;
+
+    case BUILTIN_SIZEOF:
+    case BUILTIN_ALIGNOF:
+      return this->one_arg() != NULL;
+
+    case BUILTIN_OFFSETOF:
+      {
+	Expression* arg = this->one_arg();
+	if (arg == NULL)
+	  return false;
+	return arg->field_reference_expression() != NULL;
+      }
+
+    case BUILTIN_COMPLEX:
+      {
+	const Expression_list* args = this->args();
+	if (args != NULL && args->size() == 2)
+	  return args->front()->is_constant() && args->back()->is_constant();
+      }
+      break;
+
+    case BUILTIN_REAL:
+    case BUILTIN_IMAG:
+      {
+	Expression* arg = this->one_arg();
+	return arg != NULL && arg->is_constant();
+      }
+
+    default:
+      break;
+    }
+
+  return false;
+}
+
+// Return an integer constant value if possible.
+
+bool
+Builtin_call_expression::do_integer_constant_value(bool iota_is_constant,
+						   mpz_t val,
+						   Type** ptype) const
+{
+  if (this->code_ == BUILTIN_LEN
+      || this->code_ == BUILTIN_CAP)
+    {
+      Expression* arg = this->one_arg();
+      if (arg == NULL)
+	return false;
+      Type* arg_type = arg->type();
+
+      if (this->code_ == BUILTIN_LEN && arg_type->is_string_type())
+	{
+	  std::string sval;
+	  if (arg->string_constant_value(&sval))
+	    {
+	      mpz_set_ui(val, sval.length());
+	      *ptype = Type::lookup_integer_type("int");
+	      return true;
+	    }
+	}
+
+      if (arg_type->points_to() != NULL
+	  && arg_type->points_to()->array_type() != NULL
+	  && !arg_type->points_to()->is_open_array_type())
+	arg_type = arg_type->points_to();
+
+      if (arg_type->array_type() != NULL
+	  && arg_type->array_type()->length() != NULL)
+	{
+	  if (this->seen_)
+	    return false;
+	  Expression* e = arg_type->array_type()->length();
+	  this->seen_ = true;
+	  bool r = e->integer_constant_value(iota_is_constant, val, ptype);
+	  this->seen_ = false;
+	  if (r)
+	    {
+	      *ptype = Type::lookup_integer_type("int");
+	      return true;
+	    }
+	}
+    }
+  else if (this->code_ == BUILTIN_SIZEOF
+	   || this->code_ == BUILTIN_ALIGNOF)
+    {
+      Expression* arg = this->one_arg();
+      if (arg == NULL)
+	return false;
+      Type* arg_type = arg->type();
+      if (arg_type->is_error_type() || arg_type->is_undefined())
+	return false;
+      if (arg_type->is_abstract())
+	return false;
+      if (arg_type->named_type() != NULL)
+	arg_type->named_type()->convert(this->gogo_);
+      tree arg_type_tree = arg_type->get_tree(this->gogo_);
+      if (arg_type_tree == error_mark_node)
+	return false;
+      unsigned long val_long;
+      if (this->code_ == BUILTIN_SIZEOF)
+	{
+	  tree type_size = TYPE_SIZE_UNIT(arg_type_tree);
+	  gcc_assert(TREE_CODE(type_size) == INTEGER_CST);
+	  if (TREE_INT_CST_HIGH(type_size) != 0)
+	    return false;
+	  unsigned HOST_WIDE_INT val_wide = TREE_INT_CST_LOW(type_size);
+	  val_long = static_cast<unsigned long>(val_wide);
+	  if (val_long != val_wide)
+	    return false;
+	}
+      else if (this->code_ == BUILTIN_ALIGNOF)
+	{
+	  if (arg->field_reference_expression() == NULL)
+	    val_long = go_type_alignment(arg_type_tree);
+	  else
+	    {
+	      // Calling unsafe.Alignof(s.f) returns the alignment of
+	      // the type of f when it is used as a field in a struct.
+	      val_long = go_field_alignment(arg_type_tree);
+	    }
+	}
+      else
+	gcc_unreachable();
+      mpz_set_ui(val, val_long);
+      *ptype = NULL;
+      return true;
+    }
+  else if (this->code_ == BUILTIN_OFFSETOF)
+    {
+      Expression* arg = this->one_arg();
+      if (arg == NULL)
+	return false;
+      Field_reference_expression* farg = arg->field_reference_expression();
+      if (farg == NULL)
+	return false;
+      Expression* struct_expr = farg->expr();
+      Type* st = struct_expr->type();
+      if (st->struct_type() == NULL)
+	return false;
+      if (st->named_type() != NULL)
+	st->named_type()->convert(this->gogo_);
+      tree struct_tree = st->get_tree(this->gogo_);
+      gcc_assert(TREE_CODE(struct_tree) == RECORD_TYPE);
+      tree field = TYPE_FIELDS(struct_tree);
+      for (unsigned int index = farg->field_index(); index > 0; --index)
+	{
+	  field = DECL_CHAIN(field);
+	  gcc_assert(field != NULL_TREE);
+	}
+      HOST_WIDE_INT offset_wide = int_byte_position (field);
+      if (offset_wide < 0)
+	return false;
+      unsigned long offset_long = static_cast<unsigned long>(offset_wide);
+      if (offset_long != static_cast<unsigned HOST_WIDE_INT>(offset_wide))
+	return false;
+      mpz_set_ui(val, offset_long);
+      return true;
+    }
+  return false;
+}
+
+// Return a floating point constant value if possible.
+
+bool
+Builtin_call_expression::do_float_constant_value(mpfr_t val,
+						 Type** ptype) const
+{
+  if (this->code_ == BUILTIN_REAL || this->code_ == BUILTIN_IMAG)
+    {
+      Expression* arg = this->one_arg();
+      if (arg == NULL)
+	return false;
+
+      mpfr_t real;
+      mpfr_t imag;
+      mpfr_init(real);
+      mpfr_init(imag);
+
+      bool ret = false;
+      Type* type;
+      if (arg->complex_constant_value(real, imag, &type))
+	{
+	  if (this->code_ == BUILTIN_REAL)
+	    mpfr_set(val, real, GMP_RNDN);
+	  else
+	    mpfr_set(val, imag, GMP_RNDN);
+	  *ptype = Builtin_call_expression::real_imag_type(type);
+	  ret = true;
+	}
+
+      mpfr_clear(real);
+      mpfr_clear(imag);
+      return ret;
+    }
+
+  return false;
+}
+
+// Return a complex constant value if possible.
+
+bool
+Builtin_call_expression::do_complex_constant_value(mpfr_t real, mpfr_t imag,
+						   Type** ptype) const
+{
+  if (this->code_ == BUILTIN_COMPLEX)
+    {
+      const Expression_list* args = this->args();
+      if (args == NULL || args->size() != 2)
+	return false;
+
+      mpfr_t r;
+      mpfr_init(r);
+      Type* rtype;
+      if (!args->front()->float_constant_value(r, &rtype))
+	{
+	  mpfr_clear(r);
+	  return false;
+	}
+
+      mpfr_t i;
+      mpfr_init(i);
+
+      bool ret = false;
+      Type* itype;
+      if (args->back()->float_constant_value(i, &itype)
+	  && Type::are_identical(rtype, itype, false, NULL))
+	{
+	  mpfr_set(real, r, GMP_RNDN);
+	  mpfr_set(imag, i, GMP_RNDN);
+	  *ptype = Builtin_call_expression::complex_type(rtype);
+	  ret = true;
+	}
+
+      mpfr_clear(r);
+      mpfr_clear(i);
+
+      return ret;
+    }
+
+  return false;
+}
+
+// Return the type.
+
+Type*
+Builtin_call_expression::do_type()
+{
+  switch (this->code_)
+    {
+    case BUILTIN_INVALID:
+    default:
+      gcc_unreachable();
+
+    case BUILTIN_NEW:
+    case BUILTIN_MAKE:
+      {
+	const Expression_list* args = this->args();
+	if (args == NULL || args->empty())
+	  return Type::make_error_type();
+	return Type::make_pointer_type(args->front()->type());
+      }
+
+    case BUILTIN_CAP:
+    case BUILTIN_COPY:
+    case BUILTIN_LEN:
+    case BUILTIN_ALIGNOF:
+    case BUILTIN_OFFSETOF:
+    case BUILTIN_SIZEOF:
+      return Type::lookup_integer_type("int");
+
+    case BUILTIN_CLOSE:
+    case BUILTIN_PANIC:
+    case BUILTIN_PRINT:
+    case BUILTIN_PRINTLN:
+      return Type::make_void_type();
+
+    case BUILTIN_CLOSED:
+      return Type::lookup_bool_type();
+
+    case BUILTIN_RECOVER:
+      return Type::make_interface_type(NULL, BUILTINS_LOCATION);
+
+    case BUILTIN_APPEND:
+      {
+	const Expression_list* args = this->args();
+	if (args == NULL || args->empty())
+	  return Type::make_error_type();
+	return args->front()->type();
+      }
+
+    case BUILTIN_REAL:
+    case BUILTIN_IMAG:
+      {
+	Expression* arg = this->one_arg();
+	if (arg == NULL)
+	  return Type::make_error_type();
+	Type* t = arg->type();
+	if (t->is_abstract())
+	  t = t->make_non_abstract_type();
+	t = Builtin_call_expression::real_imag_type(t);
+	if (t == NULL)
+	  t = Type::make_error_type();
+	return t;
+      }
+
+    case BUILTIN_COMPLEX:
+      {
+	const Expression_list* args = this->args();
+	if (args == NULL || args->size() != 2)
+	  return Type::make_error_type();
+	Type* t = args->front()->type();
+	if (t->is_abstract())
+	  {
+	    t = args->back()->type();
+	    if (t->is_abstract())
+	      t = t->make_non_abstract_type();
+	  }
+	t = Builtin_call_expression::complex_type(t);
+	if (t == NULL)
+	  t = Type::make_error_type();
+	return t;
+      }
+    }
+}
+
+// Determine the type.
+
+void
+Builtin_call_expression::do_determine_type(const Type_context* context)
+{
+  if (!this->determining_types())
+    return;
+
+  this->fn()->determine_type_no_context();
+
+  const Expression_list* args = this->args();
+
+  bool is_print;
+  Type* arg_type = NULL;
+  switch (this->code_)
+    {
+    case BUILTIN_PRINT:
+    case BUILTIN_PRINTLN:
+      // Do not force a large integer constant to "int".
+      is_print = true;
+      break;
+
+    case BUILTIN_REAL:
+    case BUILTIN_IMAG:
+      arg_type = Builtin_call_expression::complex_type(context->type);
+      is_print = false;
+      break;
+
+    case BUILTIN_COMPLEX:
+      {
+	// For the complex function the type of one operand can
+	// determine the type of the other, as in a binary expression.
+	arg_type = Builtin_call_expression::real_imag_type(context->type);
+	if (args != NULL && args->size() == 2)
+	  {
+	    Type* t1 = args->front()->type();
+	    Type* t2 = args->front()->type();
+	    if (!t1->is_abstract())
+	      arg_type = t1;
+	    else if (!t2->is_abstract())
+	      arg_type = t2;
+	  }
+	is_print = false;
+      }
+      break;
+
+    default:
+      is_print = false;
+      break;
+    }
+
+  if (args != NULL)
+    {
+      for (Expression_list::const_iterator pa = args->begin();
+	   pa != args->end();
+	   ++pa)
+	{
+	  Type_context subcontext;
+	  subcontext.type = arg_type;
+
+	  if (is_print)
+	    {
+	      // We want to print large constants, we so can't just
+	      // use the appropriate nonabstract type.  Use uint64 for
+	      // an integer if we know it is nonnegative, otherwise
+	      // use int64 for a integer, otherwise use float64 for a
+	      // float or complex128 for a complex.
+	      Type* want_type = NULL;
+	      Type* atype = (*pa)->type();
+	      if (atype->is_abstract())
+		{
+		  if (atype->integer_type() != NULL)
+		    {
+		      mpz_t val;
+		      mpz_init(val);
+		      Type* dummy;
+		      if (this->integer_constant_value(true, val, &dummy)
+			  && mpz_sgn(val) >= 0)
+			want_type = Type::lookup_integer_type("uint64");
+		      else
+			want_type = Type::lookup_integer_type("int64");
+		      mpz_clear(val);
+		    }
+		  else if (atype->float_type() != NULL)
+		    want_type = Type::lookup_float_type("float64");
+		  else if (atype->complex_type() != NULL)
+		    want_type = Type::lookup_complex_type("complex128");
+		  else if (atype->is_abstract_string_type())
+		    want_type = Type::lookup_string_type();
+		  else if (atype->is_abstract_boolean_type())
+		    want_type = Type::lookup_bool_type();
+		  else
+		    gcc_unreachable();
+		  subcontext.type = want_type;
+		}
+	    }
+
+	  (*pa)->determine_type(&subcontext);
+	}
+    }
+}
+
+// If there is exactly one argument, return true.  Otherwise give an
+// error message and return false.
+
+bool
+Builtin_call_expression::check_one_arg()
+{
+  const Expression_list* args = this->args();
+  if (args == NULL || args->size() < 1)
+    {
+      this->report_error(_("not enough arguments"));
+      return false;
+    }
+  else if (args->size() > 1)
+    {
+      this->report_error(_("too many arguments"));
+      return false;
+    }
+  if (args->front()->is_error_expression()
+      || args->front()->type()->is_error_type()
+      || args->front()->type()->is_undefined())
+    {
+      this->set_is_error();
+      return false;
+    }
+  return true;
+}
+
+// Check argument types for a builtin function.
+
+void
+Builtin_call_expression::do_check_types(Gogo*)
+{
+  switch (this->code_)
+    {
+    case BUILTIN_INVALID:
+    case BUILTIN_NEW:
+    case BUILTIN_MAKE:
+      return;
+
+    case BUILTIN_LEN:
+    case BUILTIN_CAP:
+      {
+	// The single argument may be either a string or an array or a
+	// map or a channel, or a pointer to a closed array.
+	if (this->check_one_arg())
+	  {
+	    Type* arg_type = this->one_arg()->type();
+	    if (arg_type->points_to() != NULL
+		&& arg_type->points_to()->array_type() != NULL
+		&& !arg_type->points_to()->is_open_array_type())
+	      arg_type = arg_type->points_to();
+	    if (this->code_ == BUILTIN_CAP)
+	      {
+		if (!arg_type->is_error_type()
+		    && arg_type->array_type() == NULL
+		    && arg_type->channel_type() == NULL)
+		  this->report_error(_("argument must be array or slice "
+				       "or channel"));
+	      }
+	    else
+	      {
+		if (!arg_type->is_error_type()
+		    && !arg_type->is_string_type()
+		    && arg_type->array_type() == NULL
+		    && arg_type->map_type() == NULL
+		    && arg_type->channel_type() == NULL)
+		  this->report_error(_("argument must be string or "
+				       "array or slice or map or channel"));
+	      }
+	  }
+      }
+      break;
+
+    case BUILTIN_PRINT:
+    case BUILTIN_PRINTLN:
+      {
+	const Expression_list* args = this->args();
+	if (args == NULL)
+	  {
+	    if (this->code_ == BUILTIN_PRINT)
+	      warning_at(this->location(), 0,
+			 "no arguments for builtin function %<%s%>",
+			 (this->code_ == BUILTIN_PRINT
+			  ? "print"
+			  : "println"));
+	  }
+	else
+	  {
+	    for (Expression_list::const_iterator p = args->begin();
+		 p != args->end();
+		 ++p)
+	      {
+		Type* type = (*p)->type();
+		if (type->is_error_type()
+		    || type->is_string_type()
+		    || type->integer_type() != NULL
+		    || type->float_type() != NULL
+		    || type->complex_type() != NULL
+		    || type->is_boolean_type()
+		    || type->points_to() != NULL
+		    || type->interface_type() != NULL
+		    || type->channel_type() != NULL
+		    || type->map_type() != NULL
+		    || type->function_type() != NULL
+		    || type->is_open_array_type())
+		  ;
+		else
+		  this->report_error(_("unsupported argument type to "
+				       "builtin function"));
+	      }
+	  }
+      }
+      break;
+
+    case BUILTIN_CLOSE:
+    case BUILTIN_CLOSED:
+      if (this->check_one_arg())
+	{
+	  if (this->one_arg()->type()->channel_type() == NULL)
+	    this->report_error(_("argument must be channel"));
+	}
+      break;
+
+    case BUILTIN_PANIC:
+    case BUILTIN_SIZEOF:
+    case BUILTIN_ALIGNOF:
+      this->check_one_arg();
+      break;
+
+    case BUILTIN_RECOVER:
+      if (this->args() != NULL && !this->args()->empty())
+	this->report_error(_("too many arguments"));
+      break;
+
+    case BUILTIN_OFFSETOF:
+      if (this->check_one_arg())
+	{
+	  Expression* arg = this->one_arg();
+	  if (arg->field_reference_expression() == NULL)
+	    this->report_error(_("argument must be a field reference"));
+	}
+      break;
+
+    case BUILTIN_COPY:
+      {
+	const Expression_list* args = this->args();
+	if (args == NULL || args->size() < 2)
+	  {
+	    this->report_error(_("not enough arguments"));
+	    break;
+	  }
+	else if (args->size() > 2)
+	  {
+	    this->report_error(_("too many arguments"));
+	    break;
+	  }
+	Type* arg1_type = args->front()->type();
+	Type* arg2_type = args->back()->type();
+	if (arg1_type->is_error_type() || arg2_type->is_error_type())
+	  break;
+
+	Type* e1;
+	if (arg1_type->is_open_array_type())
+	  e1 = arg1_type->array_type()->element_type();
+	else
+	  {
+	    this->report_error(_("left argument must be a slice"));
+	    break;
+	  }
+
+	Type* e2;
+	if (arg2_type->is_open_array_type())
+	  e2 = arg2_type->array_type()->element_type();
+	else if (arg2_type->is_string_type())
+	  e2 = Type::lookup_integer_type("uint8");
+	else
+	  {
+	    this->report_error(_("right argument must be a slice or a string"));
+	    break;
+	  }
+
+	if (!Type::are_identical(e1, e2, true, NULL))
+	  this->report_error(_("element types must be the same"));
+      }
+      break;
+
+    case BUILTIN_APPEND:
+      {
+	const Expression_list* args = this->args();
+	if (args == NULL || args->size() < 2)
+	  {
+	    this->report_error(_("not enough arguments"));
+	    break;
+	  }
+	if (args->size() > 2)
+	  {
+	    this->report_error(_("too many arguments"));
+	    break;
+	  }
+	std::string reason;
+	if (!Type::are_assignable(args->front()->type(), args->back()->type(),
+				  &reason))
+	  {
+	    if (reason.empty())
+	      this->report_error(_("arguments 1 and 2 have different types"));
+	    else
+	      {
+		error_at(this->location(),
+			 "arguments 1 and 2 have different types (%s)",
+			 reason.c_str());
+		this->set_is_error();
+	      }
+	  }
+	break;
+      }
+
+    case BUILTIN_REAL:
+    case BUILTIN_IMAG:
+      if (this->check_one_arg())
+	{
+	  if (this->one_arg()->type()->complex_type() == NULL)
+	    this->report_error(_("argument must have complex type"));
+	}
+      break;
+
+    case BUILTIN_COMPLEX:
+      {
+	const Expression_list* args = this->args();
+	if (args == NULL || args->size() < 2)
+	  this->report_error(_("not enough arguments"));
+	else if (args->size() > 2)
+	  this->report_error(_("too many arguments"));
+	else if (args->front()->is_error_expression()
+		 || args->front()->type()->is_error_type()
+		 || args->back()->is_error_expression()
+		 || args->back()->type()->is_error_type())
+	  this->set_is_error();
+	else if (!Type::are_identical(args->front()->type(),
+				      args->back()->type(), true, NULL))
+	  this->report_error(_("complex arguments must have identical types"));
+	else if (args->front()->type()->float_type() == NULL)
+	  this->report_error(_("complex arguments must have "
+			       "floating-point type"));
+      }
+      break;
+
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Return the tree for a builtin function.
+
+tree
+Builtin_call_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  source_location location = this->location();
+  switch (this->code_)
+    {
+    case BUILTIN_INVALID:
+    case BUILTIN_NEW:
+    case BUILTIN_MAKE:
+      gcc_unreachable();
+
+    case BUILTIN_LEN:
+    case BUILTIN_CAP:
+      {
+	const Expression_list* args = this->args();
+	gcc_assert(args != NULL && args->size() == 1);
+	Expression* arg = *args->begin();
+	Type* arg_type = arg->type();
+
+	if (this->seen_)
+	  {
+	    gcc_assert(saw_errors());
+	    return error_mark_node;
+	  }
+	this->seen_ = true;
+
+	tree arg_tree = arg->get_tree(context);
+
+	this->seen_ = false;
+
+	if (arg_tree == error_mark_node)
+	  return error_mark_node;
+
+	if (arg_type->points_to() != NULL)
+	  {
+	    arg_type = arg_type->points_to();
+	    gcc_assert(arg_type->array_type() != NULL
+		       && !arg_type->is_open_array_type());
+	    gcc_assert(POINTER_TYPE_P(TREE_TYPE(arg_tree)));
+	    arg_tree = build_fold_indirect_ref(arg_tree);
+	  }
+
+	tree val_tree;
+	if (this->code_ == BUILTIN_LEN)
+	  {
+	    if (arg_type->is_string_type())
+	      val_tree = String_type::length_tree(gogo, arg_tree);
+	    else if (arg_type->array_type() != NULL)
+	      {
+		if (this->seen_)
+		  {
+		    gcc_assert(saw_errors());
+		    return error_mark_node;
+		  }
+		this->seen_ = true;
+		val_tree = arg_type->array_type()->length_tree(gogo, arg_tree);
+		this->seen_ = false;
+	      }
+	    else if (arg_type->map_type() != NULL)
+	      {
+		static tree map_len_fndecl;
+		val_tree = Gogo::call_builtin(&map_len_fndecl,
+					      location,
+					      "__go_map_len",
+					      1,
+					      sizetype,
+					      arg_type->get_tree(gogo),
+					      arg_tree);
+	      }
+	    else if (arg_type->channel_type() != NULL)
+	      {
+		static tree chan_len_fndecl;
+		val_tree = Gogo::call_builtin(&chan_len_fndecl,
+					      location,
+					      "__go_chan_len",
+					      1,
+					      sizetype,
+					      arg_type->get_tree(gogo),
+					      arg_tree);
+	      }
+	    else
+	      gcc_unreachable();
+	  }
+	else
+	  {
+	    if (arg_type->array_type() != NULL)
+	      {
+		if (this->seen_)
+		  {
+		    gcc_assert(saw_errors());
+		    return error_mark_node;
+		  }
+		this->seen_ = true;
+		val_tree = arg_type->array_type()->capacity_tree(gogo,
+								 arg_tree);
+		this->seen_ = false;
+	      }
+	    else if (arg_type->channel_type() != NULL)
+	      {
+		static tree chan_cap_fndecl;
+		val_tree = Gogo::call_builtin(&chan_cap_fndecl,
+					      location,
+					      "__go_chan_cap",
+					      1,
+					      sizetype,
+					      arg_type->get_tree(gogo),
+					      arg_tree);
+	      }
+	    else
+	      gcc_unreachable();
+	  }
+
+	if (val_tree == error_mark_node)
+	  return error_mark_node;
+
+	tree type_tree = Type::lookup_integer_type("int")->get_tree(gogo);
+	if (type_tree == TREE_TYPE(val_tree))
+	  return val_tree;
+	else
+	  return fold(convert_to_integer(type_tree, val_tree));
+      }
+
+    case BUILTIN_PRINT:
+    case BUILTIN_PRINTLN:
+      {
+	const bool is_ln = this->code_ == BUILTIN_PRINTLN;
+	tree stmt_list = NULL_TREE;
+
+	const Expression_list* call_args = this->args();
+	if (call_args != NULL)
+	  {
+	    for (Expression_list::const_iterator p = call_args->begin();
+		 p != call_args->end();
+		 ++p)
+	      {
+		if (is_ln && p != call_args->begin())
+		  {
+		    static tree print_space_fndecl;
+		    tree call = Gogo::call_builtin(&print_space_fndecl,
+						   location,
+						   "__go_print_space",
+						   0,
+						   void_type_node);
+		    if (call == error_mark_node)
+		      return error_mark_node;
+		    append_to_statement_list(call, &stmt_list);
+		  }
+
+		Type* type = (*p)->type();
+
+		tree arg = (*p)->get_tree(context);
+		if (arg == error_mark_node)
+		  return error_mark_node;
+
+		tree* pfndecl;
+		const char* fnname;
+		if (type->is_string_type())
+		  {
+		    static tree print_string_fndecl;
+		    pfndecl = &print_string_fndecl;
+		    fnname = "__go_print_string";
+		  }
+		else if (type->integer_type() != NULL
+			 && type->integer_type()->is_unsigned())
+		  {
+		    static tree print_uint64_fndecl;
+		    pfndecl = &print_uint64_fndecl;
+		    fnname = "__go_print_uint64";
+		    Type* itype = Type::lookup_integer_type("uint64");
+		    arg = fold_convert_loc(location, itype->get_tree(gogo),
+					   arg);
+		  }
+		else if (type->integer_type() != NULL)
+		  {
+		    static tree print_int64_fndecl;
+		    pfndecl = &print_int64_fndecl;
+		    fnname = "__go_print_int64";
+		    Type* itype = Type::lookup_integer_type("int64");
+		    arg = fold_convert_loc(location, itype->get_tree(gogo),
+					   arg);
+		  }
+		else if (type->float_type() != NULL)
+		  {
+		    static tree print_double_fndecl;
+		    pfndecl = &print_double_fndecl;
+		    fnname = "__go_print_double";
+		    arg = fold_convert_loc(location, double_type_node, arg);
+		  }
+		else if (type->complex_type() != NULL)
+		  {
+		    static tree print_complex_fndecl;
+		    pfndecl = &print_complex_fndecl;
+		    fnname = "__go_print_complex";
+		    arg = fold_convert_loc(location, complex_double_type_node,
+					   arg);
+		  }
+		else if (type->is_boolean_type())
+		  {
+		    static tree print_bool_fndecl;
+		    pfndecl = &print_bool_fndecl;
+		    fnname = "__go_print_bool";
+		  }
+		else if (type->points_to() != NULL
+			 || type->channel_type() != NULL
+			 || type->map_type() != NULL
+			 || type->function_type() != NULL)
+		  {
+		    static tree print_pointer_fndecl;
+		    pfndecl = &print_pointer_fndecl;
+		    fnname = "__go_print_pointer";
+		    arg = fold_convert_loc(location, ptr_type_node, arg);
+		  }
+		else if (type->interface_type() != NULL)
+		  {
+		    if (type->interface_type()->is_empty())
+		      {
+			static tree print_empty_interface_fndecl;
+			pfndecl = &print_empty_interface_fndecl;
+			fnname = "__go_print_empty_interface";
+		      }
+		    else
+		      {
+			static tree print_interface_fndecl;
+			pfndecl = &print_interface_fndecl;
+			fnname = "__go_print_interface";
+		      }
+		  }
+		else if (type->is_open_array_type())
+		  {
+		    static tree print_slice_fndecl;
+		    pfndecl = &print_slice_fndecl;
+		    fnname = "__go_print_slice";
+		  }
+		else
+		  gcc_unreachable();
+
+		tree call = Gogo::call_builtin(pfndecl,
+					       location,
+					       fnname,
+					       1,
+					       void_type_node,
+					       TREE_TYPE(arg),
+					       arg);
+		if (call == error_mark_node)
+		  return error_mark_node;
+		append_to_statement_list(call, &stmt_list);
+	      }
+	  }
+
+	if (is_ln)
+	  {
+	    static tree print_nl_fndecl;
+	    tree call = Gogo::call_builtin(&print_nl_fndecl,
+					   location,
+					   "__go_print_nl",
+					   0,
+					   void_type_node);
+	    if (call == error_mark_node)
+	      return error_mark_node;
+	    append_to_statement_list(call, &stmt_list);
+	  }
+
+	return stmt_list;
+      }
+
+    case BUILTIN_PANIC:
+      {
+	const Expression_list* args = this->args();
+	gcc_assert(args != NULL && args->size() == 1);
+	Expression* arg = args->front();
+	tree arg_tree = arg->get_tree(context);
+	if (arg_tree == error_mark_node)
+	  return error_mark_node;
+	Type *empty = Type::make_interface_type(NULL, BUILTINS_LOCATION);
+	arg_tree = Expression::convert_for_assignment(context, empty,
+						      arg->type(),
+						      arg_tree, location);
+	static tree panic_fndecl;
+	tree call = Gogo::call_builtin(&panic_fndecl,
+				       location,
+				       "__go_panic",
+				       1,
+				       void_type_node,
+				       TREE_TYPE(arg_tree),
+				       arg_tree);
+	if (call == error_mark_node)
+	  return error_mark_node;
+	// This function will throw an exception.
+	TREE_NOTHROW(panic_fndecl) = 0;
+	// This function will not return.
+	TREE_THIS_VOLATILE(panic_fndecl) = 1;
+	return call;
+      }
+
+    case BUILTIN_RECOVER:
+      {
+	// The argument is set when building recover thunks.  It's a
+	// boolean value which is true if we can recover a value now.
+	const Expression_list* args = this->args();
+	gcc_assert(args != NULL && args->size() == 1);
+	Expression* arg = args->front();
+	tree arg_tree = arg->get_tree(context);
+	if (arg_tree == error_mark_node)
+	  return error_mark_node;
+
+	Type *empty = Type::make_interface_type(NULL, BUILTINS_LOCATION);
+	tree empty_tree = empty->get_tree(context->gogo());
+
+	Type* nil_type = Type::make_nil_type();
+	Expression* nil = Expression::make_nil(location);
+	tree nil_tree = nil->get_tree(context);
+	tree empty_nil_tree = Expression::convert_for_assignment(context,
+								 empty,
+								 nil_type,
+								 nil_tree,
+								 location);
+
+	// We need to handle a deferred call to recover specially,
+	// because it changes whether it can recover a panic or not.
+	// See test7 in test/recover1.go.
+	tree call;
+	if (this->is_deferred())
+	  {
+	    static tree deferred_recover_fndecl;
+	    call = Gogo::call_builtin(&deferred_recover_fndecl,
+				      location,
+				      "__go_deferred_recover",
+				      0,
+				      empty_tree);
+	  }
+	else
+	  {
+	    static tree recover_fndecl;
+	    call = Gogo::call_builtin(&recover_fndecl,
+				      location,
+				      "__go_recover",
+				      0,
+				      empty_tree);
+	  }
+	if (call == error_mark_node)
+	  return error_mark_node;
+	return fold_build3_loc(location, COND_EXPR, empty_tree, arg_tree,
+			       call, empty_nil_tree);
+      }
+
+    case BUILTIN_CLOSE:
+    case BUILTIN_CLOSED:
+      {
+	const Expression_list* args = this->args();
+	gcc_assert(args != NULL && args->size() == 1);
+	Expression* arg = args->front();
+	tree arg_tree = arg->get_tree(context);
+	if (arg_tree == error_mark_node)
+	  return error_mark_node;
+	if (this->code_ == BUILTIN_CLOSE)
+	  {
+	    static tree close_fndecl;
+	    return Gogo::call_builtin(&close_fndecl,
+				      location,
+				      "__go_builtin_close",
+				      1,
+				      void_type_node,
+				      TREE_TYPE(arg_tree),
+				      arg_tree);
+	  }
+	else
+	  {
+	    static tree closed_fndecl;
+	    return Gogo::call_builtin(&closed_fndecl,
+				      location,
+				      "__go_builtin_closed",
+				      1,
+				      boolean_type_node,
+				      TREE_TYPE(arg_tree),
+				      arg_tree);
+	  }
+      }
+
+    case BUILTIN_SIZEOF:
+    case BUILTIN_OFFSETOF:
+    case BUILTIN_ALIGNOF:
+      {
+	mpz_t val;
+	mpz_init(val);
+	Type* dummy;
+	bool b = this->integer_constant_value(true, val, &dummy);
+	if (!b)
+	  {
+	    gcc_assert(saw_errors());
+	    return error_mark_node;
+	  }
+	tree type = Type::lookup_integer_type("int")->get_tree(gogo);
+	tree ret = Expression::integer_constant_tree(val, type);
+	mpz_clear(val);
+	return ret;
+      }
+
+    case BUILTIN_COPY:
+      {
+	const Expression_list* args = this->args();
+	gcc_assert(args != NULL && args->size() == 2);
+	Expression* arg1 = args->front();
+	Expression* arg2 = args->back();
+
+	tree arg1_tree = arg1->get_tree(context);
+	tree arg2_tree = arg2->get_tree(context);
+	if (arg1_tree == error_mark_node || arg2_tree == error_mark_node)
+	  return error_mark_node;
+
+	Type* arg1_type = arg1->type();
+	Array_type* at = arg1_type->array_type();
+	arg1_tree = save_expr(arg1_tree);
+	tree arg1_val = at->value_pointer_tree(gogo, arg1_tree);
+	tree arg1_len = at->length_tree(gogo, arg1_tree);
+	if (arg1_val == error_mark_node || arg1_len == error_mark_node)
+	  return error_mark_node;
+
+	Type* arg2_type = arg2->type();
+	tree arg2_val;
+	tree arg2_len;
+	if (arg2_type->is_open_array_type())
+	  {
+	    at = arg2_type->array_type();
+	    arg2_tree = save_expr(arg2_tree);
+	    arg2_val = at->value_pointer_tree(gogo, arg2_tree);
+	    arg2_len = at->length_tree(gogo, arg2_tree);
+	  }
+	else
+	  {
+	    arg2_tree = save_expr(arg2_tree);
+	    arg2_val = String_type::bytes_tree(gogo, arg2_tree);
+	    arg2_len = String_type::length_tree(gogo, arg2_tree);
+	  }
+	if (arg2_val == error_mark_node || arg2_len == error_mark_node)
+	  return error_mark_node;
+
+	arg1_len = save_expr(arg1_len);
+	arg2_len = save_expr(arg2_len);
+	tree len = fold_build3_loc(location, COND_EXPR, TREE_TYPE(arg1_len),
+				   fold_build2_loc(location, LT_EXPR,
+						   boolean_type_node,
+						   arg1_len, arg2_len),
+				   arg1_len, arg2_len);
+	len = save_expr(len);
+
+	Type* element_type = at->element_type();
+	tree element_type_tree = element_type->get_tree(gogo);
+	if (element_type_tree == error_mark_node)
+	  return error_mark_node;
+	tree element_size = TYPE_SIZE_UNIT(element_type_tree);
+	tree bytecount = fold_convert_loc(location, TREE_TYPE(element_size),
+					  len);
+	bytecount = fold_build2_loc(location, MULT_EXPR,
+				    TREE_TYPE(element_size),
+				    bytecount, element_size);
+	bytecount = fold_convert_loc(location, size_type_node, bytecount);
+
+	arg1_val = fold_convert_loc(location, ptr_type_node, arg1_val);
+	arg2_val = fold_convert_loc(location, ptr_type_node, arg2_val);
+
+	static tree copy_fndecl;
+	tree call = Gogo::call_builtin(&copy_fndecl,
+				       location,
+				       "__go_copy",
+				       3,
+				       void_type_node,
+				       ptr_type_node,
+				       arg1_val,
+				       ptr_type_node,
+				       arg2_val,
+				       size_type_node,
+				       bytecount);
+	if (call == error_mark_node)
+	  return error_mark_node;
+
+	return fold_build2_loc(location, COMPOUND_EXPR, TREE_TYPE(len),
+			       call, len);
+      }
+
+    case BUILTIN_APPEND:
+      {
+	const Expression_list* args = this->args();
+	gcc_assert(args != NULL && args->size() == 2);
+	Expression* arg1 = args->front();
+	Expression* arg2 = args->back();
+
+	tree arg1_tree = arg1->get_tree(context);
+	tree arg2_tree = arg2->get_tree(context);
+	if (arg1_tree == error_mark_node || arg2_tree == error_mark_node)
+	  return error_mark_node;
+
+	Array_type* at = arg1->type()->array_type();
+	Type* element_type = at->element_type();
+
+	arg2_tree = Expression::convert_for_assignment(context, at,
+						       arg2->type(),
+						       arg2_tree,
+						       location);
+	if (arg2_tree == error_mark_node)
+	  return error_mark_node;
+
+	arg2_tree = save_expr(arg2_tree);
+	tree arg2_val = at->value_pointer_tree(gogo, arg2_tree);
+	tree arg2_len = at->length_tree(gogo, arg2_tree);
+	if (arg2_val == error_mark_node || arg2_len == error_mark_node)
+	  return error_mark_node;
+	arg2_val = fold_convert_loc(location, ptr_type_node, arg2_val);
+	arg2_len = fold_convert_loc(location, size_type_node, arg2_len);
+
+	tree element_type_tree = element_type->get_tree(gogo);
+	if (element_type_tree == error_mark_node)
+	  return error_mark_node;
+	tree element_size = TYPE_SIZE_UNIT(element_type_tree);
+	element_size = fold_convert_loc(location, size_type_node,
+					element_size);
+
+	// We rebuild the decl each time since the slice types may
+	// change.
+	tree append_fndecl = NULL_TREE;
+	return Gogo::call_builtin(&append_fndecl,
+				  location,
+				  "__go_append",
+				  4,
+				  TREE_TYPE(arg1_tree),
+				  TREE_TYPE(arg1_tree),
+				  arg1_tree,
+				  ptr_type_node,
+				  arg2_val,
+				  size_type_node,
+				  arg2_len,
+				  size_type_node,
+				  element_size);
+      }
+
+    case BUILTIN_REAL:
+    case BUILTIN_IMAG:
+      {
+	const Expression_list* args = this->args();
+	gcc_assert(args != NULL && args->size() == 1);
+	Expression* arg = args->front();
+	tree arg_tree = arg->get_tree(context);
+	if (arg_tree == error_mark_node)
+	  return error_mark_node;
+	gcc_assert(COMPLEX_FLOAT_TYPE_P(TREE_TYPE(arg_tree)));
+	if (this->code_ == BUILTIN_REAL)
+	  return fold_build1_loc(location, REALPART_EXPR,
+				 TREE_TYPE(TREE_TYPE(arg_tree)),
+				 arg_tree);
+	else
+	  return fold_build1_loc(location, IMAGPART_EXPR,
+				 TREE_TYPE(TREE_TYPE(arg_tree)),
+				 arg_tree);
+      }
+
+    case BUILTIN_COMPLEX:
+      {
+	const Expression_list* args = this->args();
+	gcc_assert(args != NULL && args->size() == 2);
+	tree r = args->front()->get_tree(context);
+	tree i = args->back()->get_tree(context);
+	if (r == error_mark_node || i == error_mark_node)
+	  return error_mark_node;
+	gcc_assert(TYPE_MAIN_VARIANT(TREE_TYPE(r))
+		   == TYPE_MAIN_VARIANT(TREE_TYPE(i)));
+	gcc_assert(SCALAR_FLOAT_TYPE_P(TREE_TYPE(r)));
+	return fold_build2_loc(location, COMPLEX_EXPR,
+			       build_complex_type(TREE_TYPE(r)),
+			       r, i);
+      }
+
+    default:
+      gcc_unreachable();
+    }
+}
+
+// We have to support exporting a builtin call expression, because
+// code can set a constant to the result of a builtin expression.
+
+void
+Builtin_call_expression::do_export(Export* exp) const
+{
+  bool ok = false;
+
+  mpz_t val;
+  mpz_init(val);
+  Type* dummy;
+  if (this->integer_constant_value(true, val, &dummy))
+    {
+      Integer_expression::export_integer(exp, val);
+      ok = true;
+    }
+  mpz_clear(val);
+
+  if (!ok)
+    {
+      mpfr_t fval;
+      mpfr_init(fval);
+      if (this->float_constant_value(fval, &dummy))
+	{
+	  Float_expression::export_float(exp, fval);
+	  ok = true;
+	}
+      mpfr_clear(fval);
+    }
+
+  if (!ok)
+    {
+      mpfr_t real;
+      mpfr_t imag;
+      mpfr_init(real);
+      mpfr_init(imag);
+      if (this->complex_constant_value(real, imag, &dummy))
+	{
+	  Complex_expression::export_complex(exp, real, imag);
+	  ok = true;
+	}
+      mpfr_clear(real);
+      mpfr_clear(imag);
+    }
+
+  if (!ok)
+    {
+      error_at(this->location(), "value is not constant");
+      return;
+    }
+
+  // A trailing space lets us reliably identify the end of the number.
+  exp->write_c_string(" ");
+}
+
+// Class Call_expression.
+
+// Traversal.
+
+int
+Call_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->fn_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (this->args_ != NULL)
+    {
+      if (this->args_->traverse(traverse) == TRAVERSE_EXIT)
+	return TRAVERSE_EXIT;
+    }
+  return TRAVERSE_CONTINUE;
+}
+
+// Lower a call statement.
+
+Expression*
+Call_expression::do_lower(Gogo* gogo, Named_object* function, int)
+{
+  // A type case can look like a function call.
+  if (this->fn_->is_type_expression()
+      && this->args_ != NULL
+      && this->args_->size() == 1)
+    return Expression::make_cast(this->fn_->type(), this->args_->front(),
+				 this->location());
+
+  // Recognize a call to a builtin function.
+  Func_expression* fne = this->fn_->func_expression();
+  if (fne != NULL
+      && fne->named_object()->is_function_declaration()
+      && fne->named_object()->func_declaration_value()->type()->is_builtin())
+    return new Builtin_call_expression(gogo, this->fn_, this->args_,
+				       this->is_varargs_, this->location());
+
+  // Handle an argument which is a call to a function which returns
+  // multiple results.
+  if (this->args_ != NULL
+      && this->args_->size() == 1
+      && this->args_->front()->call_expression() != NULL
+      && this->fn_->type()->function_type() != NULL)
+    {
+      Function_type* fntype = this->fn_->type()->function_type();
+      size_t rc = this->args_->front()->call_expression()->result_count();
+      if (rc > 1
+	  && fntype->parameters() != NULL
+	  && (fntype->parameters()->size() == rc
+	      || (fntype->is_varargs()
+		  && fntype->parameters()->size() - 1 <= rc)))
+	{
+	  Call_expression* call = this->args_->front()->call_expression();
+	  Expression_list* args = new Expression_list;
+	  for (size_t i = 0; i < rc; ++i)
+	    args->push_back(Expression::make_call_result(call, i));
+	  // We can't return a new call expression here, because this
+	  // one may be referenced by Call_result expressions.  We
+	  // also can't delete the old arguments, because we may still
+	  // traverse them somewhere up the call stack.  FIXME.
+	  this->args_ = args;
+	}
+    }
+
+  // Handle a call to a varargs function by packaging up the extra
+  // parameters.
+  if (this->fn_->type()->function_type() != NULL
+      && this->fn_->type()->function_type()->is_varargs())
+    {
+      Function_type* fntype = this->fn_->type()->function_type();
+      const Typed_identifier_list* parameters = fntype->parameters();
+      gcc_assert(parameters != NULL && !parameters->empty());
+      Type* varargs_type = parameters->back().type();
+      return this->lower_varargs(gogo, function, varargs_type,
+				 parameters->size());
+    }
+
+  return this;
+}
+
+// Lower a call to a varargs function.  FUNCTION is the function in
+// which the call occurs--it's not the function we are calling.
+// VARARGS_TYPE is the type of the varargs parameter, a slice type.
+// PARAM_COUNT is the number of parameters of the function we are
+// calling; the last of these parameters will be the varargs
+// parameter.
+
+Expression*
+Call_expression::lower_varargs(Gogo* gogo, Named_object* function,
+			       Type* varargs_type, size_t param_count)
+{
+  if (this->varargs_are_lowered_)
+    return this;
+
+  source_location loc = this->location();
+
+  gcc_assert(param_count > 0);
+  gcc_assert(varargs_type->is_open_array_type());
+
+  size_t arg_count = this->args_ == NULL ? 0 : this->args_->size();
+  if (arg_count < param_count - 1)
+    {
+      // Not enough arguments; will be caught in check_types.
+      return this;
+    }
+
+  Expression_list* old_args = this->args_;
+  Expression_list* new_args = new Expression_list();
+  bool push_empty_arg = false;
+  if (old_args == NULL || old_args->empty())
+    {
+      gcc_assert(param_count == 1);
+      push_empty_arg = true;
+    }
+  else
+    {
+      Expression_list::const_iterator pa;
+      int i = 1;
+      for (pa = old_args->begin(); pa != old_args->end(); ++pa, ++i)
+	{
+	  if (static_cast<size_t>(i) == param_count)
+	    break;
+	  new_args->push_back(*pa);
+	}
+
+      // We have reached the varargs parameter.
+
+      bool issued_error = false;
+      if (pa == old_args->end())
+	push_empty_arg = true;
+      else if (pa + 1 == old_args->end() && this->is_varargs_)
+	new_args->push_back(*pa);
+      else if (this->is_varargs_)
+	{
+	  this->report_error(_("too many arguments"));
+	  return this;
+	}
+      else
+	{
+	  Type* element_type = varargs_type->array_type()->element_type();
+	  Expression_list* vals = new Expression_list;
+	  for (; pa != old_args->end(); ++pa, ++i)
+	    {
+	      // Check types here so that we get a better message.
+	      Type* patype = (*pa)->type();
+	      source_location paloc = (*pa)->location();
+	      if (!this->check_argument_type(i, element_type, patype,
+					     paloc, issued_error))
+		continue;
+	      vals->push_back(*pa);
+	    }
+	  Expression* val =
+	    Expression::make_slice_composite_literal(varargs_type, vals, loc);
+	  new_args->push_back(val);
+	}
+    }
+
+  if (push_empty_arg)
+    new_args->push_back(Expression::make_nil(loc));
+
+  // We can't return a new call expression here, because this one may
+  // be referenced by Call_result expressions.  FIXME.
+  if (old_args != NULL)
+    delete old_args;
+  this->args_ = new_args;
+  this->varargs_are_lowered_ = true;
+
+  // Lower all the new subexpressions.
+  Expression* ret = this;
+  gogo->lower_expression(function, &ret);
+  gcc_assert(ret == this);
+  return ret;
+}
+
+// Get the function type.  Returns NULL if we don't know the type.  If
+// this returns NULL, and if_ERROR is true, issues an error.
+
+Function_type*
+Call_expression::get_function_type() const
+{
+  return this->fn_->type()->function_type();
+}
+
+// Return the number of values which this call will return.
+
+size_t
+Call_expression::result_count() const
+{
+  const Function_type* fntype = this->get_function_type();
+  if (fntype == NULL)
+    return 0;
+  if (fntype->results() == NULL)
+    return 0;
+  return fntype->results()->size();
+}
+
+// Return whether this is a call to the predeclared function recover.
+
+bool
+Call_expression::is_recover_call() const
+{
+  return this->do_is_recover_call();
+}
+
+// Set the argument to the recover function.
+
+void
+Call_expression::set_recover_arg(Expression* arg)
+{
+  this->do_set_recover_arg(arg);
+}
+
+// Virtual functions also implemented by Builtin_call_expression.
+
+bool
+Call_expression::do_is_recover_call() const
+{
+  return false;
+}
+
+void
+Call_expression::do_set_recover_arg(Expression*)
+{
+  gcc_unreachable();
+}
+
+// Get the type.
+
+Type*
+Call_expression::do_type()
+{
+  if (this->type_ != NULL)
+    return this->type_;
+
+  Type* ret;
+  Function_type* fntype = this->get_function_type();
+  if (fntype == NULL)
+    return Type::make_error_type();
+
+  const Typed_identifier_list* results = fntype->results();
+  if (results == NULL)
+    ret = Type::make_void_type();
+  else if (results->size() == 1)
+    ret = results->begin()->type();
+  else
+    ret = Type::make_call_multiple_result_type(this);
+
+  this->type_ = ret;
+
+  return this->type_;
+}
+
+// Determine types for a call expression.  We can use the function
+// parameter types to set the types of the arguments.
+
+void
+Call_expression::do_determine_type(const Type_context*)
+{
+  if (!this->determining_types())
+    return;
+
+  this->fn_->determine_type_no_context();
+  Function_type* fntype = this->get_function_type();
+  const Typed_identifier_list* parameters = NULL;
+  if (fntype != NULL)
+    parameters = fntype->parameters();
+  if (this->args_ != NULL)
+    {
+      Typed_identifier_list::const_iterator pt;
+      if (parameters != NULL)
+	pt = parameters->begin();
+      for (Expression_list::const_iterator pa = this->args_->begin();
+	   pa != this->args_->end();
+	   ++pa)
+	{
+	  if (parameters != NULL && pt != parameters->end())
+	    {
+	      Type_context subcontext(pt->type(), false);
+	      (*pa)->determine_type(&subcontext);
+	      ++pt;
+	    }
+	  else
+	    (*pa)->determine_type_no_context();
+	}
+    }
+}
+
+// Called when determining types for a Call_expression.  Return true
+// if we should go ahead, false if they have already been determined.
+
+bool
+Call_expression::determining_types()
+{
+  if (this->types_are_determined_)
+    return false;
+  else
+    {
+      this->types_are_determined_ = true;
+      return true;
+    }
+}
+
+// Check types for parameter I.
+
+bool
+Call_expression::check_argument_type(int i, const Type* parameter_type,
+				     const Type* argument_type,
+				     source_location argument_location,
+				     bool issued_error)
+{
+  std::string reason;
+  if (!Type::are_assignable(parameter_type, argument_type, &reason))
+    {
+      if (!issued_error)
+	{
+	  if (reason.empty())
+	    error_at(argument_location, "argument %d has incompatible type", i);
+	  else
+	    error_at(argument_location,
+		     "argument %d has incompatible type (%s)",
+		     i, reason.c_str());
+	}
+      this->set_is_error();
+      return false;
+    }
+  return true;
+}
+
+// Check types.
+
+void
+Call_expression::do_check_types(Gogo*)
+{
+  Function_type* fntype = this->get_function_type();
+  if (fntype == NULL)
+    {
+      if (!this->fn_->type()->is_error_type())
+	this->report_error(_("expected function"));
+      return;
+    }
+
+  if (fntype->is_method())
+    {
+      // We don't support pointers to methods, so the function has to
+      // be a bound method expression.
+      Bound_method_expression* bme = this->fn_->bound_method_expression();
+      if (bme == NULL)
+	{
+	  this->report_error(_("method call without object"));
+	  return;
+	}
+      Type* first_arg_type = bme->first_argument()->type();
+      if (first_arg_type->points_to() == NULL)
+	{
+	  // When passing a value, we need to check that we are
+	  // permitted to copy it.
+	  std::string reason;
+	  if (!Type::are_assignable(fntype->receiver()->type(),
+				    first_arg_type, &reason))
+	    {
+	      if (reason.empty())
+		this->report_error(_("incompatible type for receiver"));
+	      else
+		{
+		  error_at(this->location(),
+			   "incompatible type for receiver (%s)",
+			   reason.c_str());
+		  this->set_is_error();
+		}
+	    }
+	}
+    }
+
+  // Note that varargs was handled by the lower_varargs() method, so
+  // we don't have to worry about it here.
+
+  const Typed_identifier_list* parameters = fntype->parameters();
+  if (this->args_ == NULL)
+    {
+      if (parameters != NULL && !parameters->empty())
+	this->report_error(_("not enough arguments"));
+    }
+  else if (parameters == NULL)
+    this->report_error(_("too many arguments"));
+  else
+    {
+      int i = 0;
+      Typed_identifier_list::const_iterator pt = parameters->begin();
+      for (Expression_list::const_iterator pa = this->args_->begin();
+	   pa != this->args_->end();
+	   ++pa, ++pt, ++i)
+	{
+	  if (pt == parameters->end())
+	    {
+	      this->report_error(_("too many arguments"));
+	      return;
+	    }
+	  this->check_argument_type(i + 1, pt->type(), (*pa)->type(),
+				    (*pa)->location(), false);
+	}
+      if (pt != parameters->end())
+	this->report_error(_("not enough arguments"));
+    }
+}
+
+// Return whether we have to use a temporary variable to ensure that
+// we evaluate this call expression in order.  If the call returns no
+// results then it will inevitably be executed last.  If the call
+// returns more than one result then it will be used with Call_result
+// expressions.  So we only have to use a temporary variable if the
+// call returns exactly one result.
+
+bool
+Call_expression::do_must_eval_in_order() const
+{
+  return this->result_count() == 1;
+}
+
+// Get the function and the first argument to use when calling a bound
+// method.
+
+tree
+Call_expression::bound_method_function(Translate_context* context,
+				       Bound_method_expression* bound_method,
+				       tree* first_arg_ptr)
+{
+  Expression* first_argument = bound_method->first_argument();
+  tree first_arg = first_argument->get_tree(context);
+  if (first_arg == error_mark_node)
+    return error_mark_node;
+
+  // We always pass a pointer to the first argument when calling a
+  // method.
+  if (first_argument->type()->points_to() == NULL)
+    {
+      tree pointer_to_arg_type = build_pointer_type(TREE_TYPE(first_arg));
+      if (TREE_ADDRESSABLE(TREE_TYPE(first_arg))
+	  || DECL_P(first_arg)
+	  || TREE_CODE(first_arg) == INDIRECT_REF
+	  || TREE_CODE(first_arg) == COMPONENT_REF)
+	{
+	  first_arg = build_fold_addr_expr(first_arg);
+	  if (DECL_P(first_arg))
+	    TREE_ADDRESSABLE(first_arg) = 1;
+	}
+      else
+	{
+	  tree tmp = create_tmp_var(TREE_TYPE(first_arg),
+				    get_name(first_arg));
+	  DECL_IGNORED_P(tmp) = 0;
+	  DECL_INITIAL(tmp) = first_arg;
+	  first_arg = build2(COMPOUND_EXPR, pointer_to_arg_type,
+			     build1(DECL_EXPR, void_type_node, tmp),
+			     build_fold_addr_expr(tmp));
+	  TREE_ADDRESSABLE(tmp) = 1;
+	}
+      if (first_arg == error_mark_node)
+	return error_mark_node;
+    }
+
+  Type* fatype = bound_method->first_argument_type();
+  if (fatype != NULL)
+    {
+      if (fatype->points_to() == NULL)
+	fatype = Type::make_pointer_type(fatype);
+      first_arg = fold_convert(fatype->get_tree(context->gogo()), first_arg);
+      if (first_arg == error_mark_node
+	  || TREE_TYPE(first_arg) == error_mark_node)
+	return error_mark_node;
+    }
+
+  *first_arg_ptr = first_arg;
+
+  return bound_method->method()->get_tree(context);
+}
+
+// Get the function and the first argument to use when calling an
+// interface method.
+
+tree
+Call_expression::interface_method_function(
+    Translate_context* context,
+    Interface_field_reference_expression* interface_method,
+    tree* first_arg_ptr)
+{
+  tree expr = interface_method->expr()->get_tree(context);
+  if (expr == error_mark_node)
+    return error_mark_node;
+  expr = save_expr(expr);
+  tree first_arg = interface_method->get_underlying_object_tree(context, expr);
+  if (first_arg == error_mark_node)
+    return error_mark_node;
+  *first_arg_ptr = first_arg;
+  return interface_method->get_function_tree(context, expr);
+}
+
+// Build the call expression.
+
+tree
+Call_expression::do_get_tree(Translate_context* context)
+{
+  if (this->tree_ != NULL_TREE)
+    return this->tree_;
+
+  Function_type* fntype = this->get_function_type();
+  if (fntype == NULL)
+    return error_mark_node;
+
+  if (this->fn_->is_error_expression())
+    return error_mark_node;
+
+  Gogo* gogo = context->gogo();
+  source_location location = this->location();
+
+  Func_expression* func = this->fn_->func_expression();
+  Bound_method_expression* bound_method = this->fn_->bound_method_expression();
+  Interface_field_reference_expression* interface_method =
+    this->fn_->interface_field_reference_expression();
+  const bool has_closure = func != NULL && func->closure() != NULL;
+  const bool is_method = bound_method != NULL || interface_method != NULL;
+  gcc_assert(!fntype->is_method() || is_method);
+
+  int nargs;
+  tree* args;
+  if (this->args_ == NULL || this->args_->empty())
+    {
+      nargs = is_method ? 1 : 0;
+      args = nargs == 0 ? NULL : new tree[nargs];
+    }
+  else
+    {
+      const Typed_identifier_list* params = fntype->parameters();
+      gcc_assert(params != NULL);
+
+      nargs = this->args_->size();
+      int i = is_method ? 1 : 0;
+      nargs += i;
+      args = new tree[nargs];
+
+      Typed_identifier_list::const_iterator pp = params->begin();
+      Expression_list::const_iterator pe;
+      for (pe = this->args_->begin();
+	   pe != this->args_->end();
+	   ++pe, ++pp, ++i)
+	{
+	  gcc_assert(pp != params->end());
+	  tree arg_val = (*pe)->get_tree(context);
+	  args[i] = Expression::convert_for_assignment(context,
+						       pp->type(),
+						       (*pe)->type(),
+						       arg_val,
+						       location);
+	  if (args[i] == error_mark_node)
+	    {
+	      delete[] args;
+	      return error_mark_node;
+	    }
+	}
+      gcc_assert(pp == params->end());
+      gcc_assert(i == nargs);
+    }
+
+  tree rettype = TREE_TYPE(TREE_TYPE(fntype->get_tree(gogo)));
+  if (rettype == error_mark_node)
+    {
+      delete[] args;
+      return error_mark_node;
+    }
+
+  tree fn;
+  if (has_closure)
+    fn = func->get_tree_without_closure(gogo);
+  else if (!is_method)
+    fn = this->fn_->get_tree(context);
+  else if (bound_method != NULL)
+    fn = this->bound_method_function(context, bound_method, &args[0]);
+  else if (interface_method != NULL)
+    fn = this->interface_method_function(context, interface_method, &args[0]);
+  else
+    gcc_unreachable();
+
+  if (fn == error_mark_node || TREE_TYPE(fn) == error_mark_node)
+    {
+      delete[] args;
+      return error_mark_node;
+    }
+
+  tree fndecl = fn;
+  if (TREE_CODE(fndecl) == ADDR_EXPR)
+    fndecl = TREE_OPERAND(fndecl, 0);
+
+  // Add a type cast in case the type of the function is a recursive
+  // type which refers to itself.
+  if (!DECL_P(fndecl) || !DECL_IS_BUILTIN(fndecl))
+    {
+      tree fnt = fntype->get_tree(gogo);
+      if (fnt == error_mark_node)
+	return error_mark_node;
+      fn = fold_convert_loc(location, fnt, fn);
+    }
+
+  // This is to support builtin math functions when using 80387 math.
+  tree excess_type = NULL_TREE;
+  if (DECL_P(fndecl)
+      && DECL_IS_BUILTIN(fndecl)
+      && DECL_BUILT_IN_CLASS(fndecl) == BUILT_IN_NORMAL
+      && nargs > 0
+      && ((SCALAR_FLOAT_TYPE_P(rettype)
+	   && SCALAR_FLOAT_TYPE_P(TREE_TYPE(args[0])))
+	  || (COMPLEX_FLOAT_TYPE_P(rettype)
+	      && COMPLEX_FLOAT_TYPE_P(TREE_TYPE(args[0])))))
+    {
+      excess_type = excess_precision_type(TREE_TYPE(args[0]));
+      if (excess_type != NULL_TREE)
+	{
+	  tree excess_fndecl = mathfn_built_in(excess_type,
+					       DECL_FUNCTION_CODE(fndecl));
+	  if (excess_fndecl == NULL_TREE)
+	    excess_type = NULL_TREE;
+	  else
+	    {
+	      fn = build_fold_addr_expr_loc(location, excess_fndecl);
+	      for (int i = 0; i < nargs; ++i)
+		args[i] = ::convert(excess_type, args[i]);
+	    }
+	}
+    }
+
+  tree ret = build_call_array(excess_type != NULL_TREE ? excess_type : rettype,
+			      fn, nargs, args);
+  delete[] args;
+
+  SET_EXPR_LOCATION(ret, location);
+
+  if (has_closure)
+    {
+      tree closure_tree = func->closure()->get_tree(context);
+      if (closure_tree != error_mark_node)
+	CALL_EXPR_STATIC_CHAIN(ret) = closure_tree;
+    }
+
+  // If this is a recursive function type which returns itself, as in
+  //   type F func() F
+  // we have used ptr_type_node for the return type.  Add a cast here
+  // to the correct type.
+  if (TREE_TYPE(ret) == ptr_type_node)
+    {
+      tree t = this->type()->base()->get_tree(gogo);
+      ret = fold_convert_loc(location, t, ret);
+    }
+
+  if (excess_type != NULL_TREE)
+    {
+      // Calling convert here can undo our excess precision change.
+      // That may or may not be a bug in convert_to_real.
+      ret = build1(NOP_EXPR, rettype, ret);
+    }
+
+  // If there is more than one result, we will refer to the call
+  // multiple times.
+  if (fntype->results() != NULL && fntype->results()->size() > 1)
+    ret = save_expr(ret);
+
+  this->tree_ = ret;
+
+  return ret;
+}
+
+// Make a call expression.
+
+Call_expression*
+Expression::make_call(Expression* fn, Expression_list* args, bool is_varargs,
+		      source_location location)
+{
+  return new Call_expression(fn, args, is_varargs, location);
+}
+
+// A single result from a call which returns multiple results.
+
+class Call_result_expression : public Expression
+{
+ public:
+  Call_result_expression(Call_expression* call, unsigned int index)
+    : Expression(EXPRESSION_CALL_RESULT, call->location()),
+      call_(call), index_(index)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse*);
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return new Call_result_expression(this->call_->call_expression(),
+				      this->index_);
+  }
+
+  bool
+  do_must_eval_in_order() const
+  { return true; }
+
+  tree
+  do_get_tree(Translate_context*);
+
+ private:
+  // The underlying call expression.
+  Expression* call_;
+  // Which result we want.
+  unsigned int index_;
+};
+
+// Traverse a call result.
+
+int
+Call_result_expression::do_traverse(Traverse* traverse)
+{
+  if (traverse->remember_expression(this->call_))
+    {
+      // We have already traversed the call expression.
+      return TRAVERSE_CONTINUE;
+    }
+  return Expression::traverse(&this->call_, traverse);
+}
+
+// Get the type.
+
+Type*
+Call_result_expression::do_type()
+{
+  if (this->classification() == EXPRESSION_ERROR)
+    return Type::make_error_type();
+
+  // THIS->CALL_ can be replaced with a temporary reference due to
+  // Call_expression::do_must_eval_in_order when there is an error.
+  Call_expression* ce = this->call_->call_expression();
+  if (ce == NULL)
+    {
+      this->set_is_error();
+      return Type::make_error_type();
+    }
+  Function_type* fntype = ce->get_function_type();
+  if (fntype == NULL)
+    {
+      this->set_is_error();
+      return Type::make_error_type();
+    }
+  const Typed_identifier_list* results = fntype->results();
+  if (results == NULL)
+    {
+      this->report_error(_("number of results does not match "
+			   "number of values"));
+      return Type::make_error_type();
+    }
+  Typed_identifier_list::const_iterator pr = results->begin();
+  for (unsigned int i = 0; i < this->index_; ++i)
+    {
+      if (pr == results->end())
+	break;
+      ++pr;
+    }
+  if (pr == results->end())
+    {
+      this->report_error(_("number of results does not match "
+			   "number of values"));
+      return Type::make_error_type();
+    }
+  return pr->type();
+}
+
+// Check the type.  Just make sure that we trigger the warning in
+// do_type.
+
+void
+Call_result_expression::do_check_types(Gogo*)
+{
+  this->type();
+}
+
+// Determine the type.  We have nothing to do here, but the 0 result
+// needs to pass down to the caller.
+
+void
+Call_result_expression::do_determine_type(const Type_context*)
+{
+  this->call_->determine_type_no_context();
+}
+
+// Return the tree.
+
+tree
+Call_result_expression::do_get_tree(Translate_context* context)
+{
+  tree call_tree = this->call_->get_tree(context);
+  if (call_tree == error_mark_node)
+    return error_mark_node;
+  if (TREE_CODE(TREE_TYPE(call_tree)) != RECORD_TYPE)
+    {
+      gcc_assert(saw_errors());
+      return error_mark_node;
+    }
+  tree field = TYPE_FIELDS(TREE_TYPE(call_tree));
+  for (unsigned int i = 0; i < this->index_; ++i)
+    {
+      gcc_assert(field != NULL_TREE);
+      field = DECL_CHAIN(field);
+    }
+  gcc_assert(field != NULL_TREE);
+  return build3(COMPONENT_REF, TREE_TYPE(field), call_tree, field, NULL_TREE);
+}
+
+// Make a reference to a single result of a call which returns
+// multiple results.
+
+Expression*
+Expression::make_call_result(Call_expression* call, unsigned int index)
+{
+  return new Call_result_expression(call, index);
+}
+
+// Class Index_expression.
+
+// Traversal.
+
+int
+Index_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->left_, traverse) == TRAVERSE_EXIT
+      || Expression::traverse(&this->start_, traverse) == TRAVERSE_EXIT
+      || (this->end_ != NULL
+	  && Expression::traverse(&this->end_, traverse) == TRAVERSE_EXIT))
+    return TRAVERSE_EXIT;
+  return TRAVERSE_CONTINUE;
+}
+
+// Lower an index expression.  This converts the generic index
+// expression into an array index, a string index, or a map index.
+
+Expression*
+Index_expression::do_lower(Gogo*, Named_object*, int)
+{
+  source_location location = this->location();
+  Expression* left = this->left_;
+  Expression* start = this->start_;
+  Expression* end = this->end_;
+
+  Type* type = left->type();
+  if (type->is_error_type())
+    return Expression::make_error(location);
+  else if (left->is_type_expression())
+    {
+      error_at(location, "attempt to index type expression");
+      return Expression::make_error(location);
+    }
+  else if (type->array_type() != NULL)
+    return Expression::make_array_index(left, start, end, location);
+  else if (type->points_to() != NULL
+	   && type->points_to()->array_type() != NULL
+	   && !type->points_to()->is_open_array_type())
+    {
+      Expression* deref = Expression::make_unary(OPERATOR_MULT, left,
+						 location);
+      return Expression::make_array_index(deref, start, end, location);
+    }
+  else if (type->is_string_type())
+    return Expression::make_string_index(left, start, end, location);
+  else if (type->map_type() != NULL)
+    {
+      if (end != NULL)
+	{
+	  error_at(location, "invalid slice of map");
+	  return Expression::make_error(location);
+	}
+      Map_index_expression* ret= Expression::make_map_index(left, start,
+							    location);
+      if (this->is_lvalue_)
+	ret->set_is_lvalue();
+      return ret;
+    }
+  else
+    {
+      error_at(location,
+	       "attempt to index object which is not array, string, or map");
+      return Expression::make_error(location);
+    }
+}
+
+// Make an index expression.
+
+Expression*
+Expression::make_index(Expression* left, Expression* start, Expression* end,
+		       source_location location)
+{
+  return new Index_expression(left, start, end, location);
+}
+
+// An array index.  This is used for both indexing and slicing.
+
+class Array_index_expression : public Expression
+{
+ public:
+  Array_index_expression(Expression* array, Expression* start,
+			 Expression* end, source_location location)
+    : Expression(EXPRESSION_ARRAY_INDEX, location),
+      array_(array), start_(start), end_(end), type_(NULL)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse*);
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return Expression::make_array_index(this->array_->copy(),
+					this->start_->copy(),
+					(this->end_ == NULL
+					 ? NULL
+					 : this->end_->copy()),
+					this->location());
+  }
+
+  bool
+  do_is_addressable() const;
+
+  void
+  do_address_taken(bool escapes)
+  { this->array_->address_taken(escapes); }
+
+  tree
+  do_get_tree(Translate_context*);
+
+ private:
+  // The array we are getting a value from.
+  Expression* array_;
+  // The start or only index.
+  Expression* start_;
+  // The end index of a slice.  This may be NULL for a simple array
+  // index, or it may be a nil expression for the length of the array.
+  Expression* end_;
+  // The type of the expression.
+  Type* type_;
+};
+
+// Array index traversal.
+
+int
+Array_index_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->array_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (Expression::traverse(&this->start_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (this->end_ != NULL)
+    {
+      if (Expression::traverse(&this->end_, traverse) == TRAVERSE_EXIT)
+	return TRAVERSE_EXIT;
+    }
+  return TRAVERSE_CONTINUE;
+}
+
+// Return the type of an array index.
+
+Type*
+Array_index_expression::do_type()
+{
+  if (this->type_ == NULL)
+    {
+     Array_type* type = this->array_->type()->array_type();
+      if (type == NULL)
+	this->type_ = Type::make_error_type();
+      else if (this->end_ == NULL)
+	this->type_ = type->element_type();
+      else if (type->is_open_array_type())
+	{
+	  // A slice of a slice has the same type as the original
+	  // slice.
+	  this->type_ = this->array_->type()->deref();
+	}
+      else
+	{
+	  // A slice of an array is a slice.
+	  this->type_ = Type::make_array_type(type->element_type(), NULL);
+	}
+    }
+  return this->type_;
+}
+
+// Set the type of an array index.
+
+void
+Array_index_expression::do_determine_type(const Type_context*)
+{
+  this->array_->determine_type_no_context();
+  this->start_->determine_type_no_context();
+  if (this->end_ != NULL)
+    this->end_->determine_type_no_context();
+}
+
+// Check types of an array index.
+
+void
+Array_index_expression::do_check_types(Gogo*)
+{
+  if (this->start_->type()->integer_type() == NULL)
+    this->report_error(_("index must be integer"));
+  if (this->end_ != NULL
+      && this->end_->type()->integer_type() == NULL
+      && !this->end_->is_nil_expression())
+    this->report_error(_("slice end must be integer"));
+
+  Array_type* array_type = this->array_->type()->array_type();
+  if (array_type == NULL)
+    {
+      gcc_assert(this->array_->type()->is_error_type());
+      return;
+    }
+
+  unsigned int int_bits =
+    Type::lookup_integer_type("int")->integer_type()->bits();
+
+  Type* dummy;
+  mpz_t lval;
+  mpz_init(lval);
+  bool lval_valid = (array_type->length() != NULL
+		     && array_type->length()->integer_constant_value(true,
+								     lval,
+								     &dummy));
+  mpz_t ival;
+  mpz_init(ival);
+  if (this->start_->integer_constant_value(true, ival, &dummy))
+    {
+      if (mpz_sgn(ival) < 0
+	  || mpz_sizeinbase(ival, 2) >= int_bits
+	  || (lval_valid
+	      && (this->end_ == NULL
+		  ? mpz_cmp(ival, lval) >= 0
+		  : mpz_cmp(ival, lval) > 0)))
+	{
+	  error_at(this->start_->location(), "array index out of bounds");
+	  this->set_is_error();
+	}
+    }
+  if (this->end_ != NULL && !this->end_->is_nil_expression())
+    {
+      if (this->end_->integer_constant_value(true, ival, &dummy))
+	{
+	  if (mpz_sgn(ival) < 0
+	      || mpz_sizeinbase(ival, 2) >= int_bits
+	      || (lval_valid && mpz_cmp(ival, lval) > 0))
+	    {
+	      error_at(this->end_->location(), "array index out of bounds");
+	      this->set_is_error();
+	    }
+	}
+    }
+  mpz_clear(ival);
+  mpz_clear(lval);
+
+  // A slice of an array requires an addressable array.  A slice of a
+  // slice is always possible.
+  if (this->end_ != NULL
+      && !array_type->is_open_array_type()
+      && !this->array_->is_addressable())
+    this->report_error(_("array is not addressable"));
+}
+
+// Return whether this expression is addressable.
+
+bool
+Array_index_expression::do_is_addressable() const
+{
+  // A slice expression is not addressable.
+  if (this->end_ != NULL)
+    return false;
+
+  // An index into a slice is addressable.
+  if (this->array_->type()->is_open_array_type())
+    return true;
+
+  // An index into an array is addressable if the array is
+  // addressable.
+  return this->array_->is_addressable();
+}
+
+// Get a tree for an array index.
+
+tree
+Array_index_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  source_location loc = this->location();
+
+  Array_type* array_type = this->array_->type()->array_type();
+  if (array_type == NULL)
+    {
+      gcc_assert(this->array_->type()->is_error_type());
+      return error_mark_node;
+    }
+
+  tree type_tree = array_type->get_tree(gogo);
+  if (type_tree == error_mark_node)
+    return error_mark_node;
+
+  tree array_tree = this->array_->get_tree(context);
+  if (array_tree == error_mark_node)
+    return error_mark_node;
+
+  if (array_type->length() == NULL && !DECL_P(array_tree))
+    array_tree = save_expr(array_tree);
+  tree length_tree = array_type->length_tree(gogo, array_tree);
+  if (length_tree == error_mark_node)
+    return error_mark_node;
+  length_tree = save_expr(length_tree);
+  tree length_type = TREE_TYPE(length_tree);
+
+  tree bad_index = boolean_false_node;
+
+  tree start_tree = this->start_->get_tree(context);
+  if (start_tree == error_mark_node)
+    return error_mark_node;
+  if (!DECL_P(start_tree))
+    start_tree = save_expr(start_tree);
+  if (!INTEGRAL_TYPE_P(TREE_TYPE(start_tree)))
+    start_tree = convert_to_integer(length_type, start_tree);
+
+  bad_index = Expression::check_bounds(start_tree, length_type, bad_index,
+				       loc);
+
+  start_tree = fold_convert_loc(loc, length_type, start_tree);
+  bad_index = fold_build2_loc(loc, TRUTH_OR_EXPR, boolean_type_node, bad_index,
+			      fold_build2_loc(loc,
+					      (this->end_ == NULL
+					       ? GE_EXPR
+					       : GT_EXPR),
+					      boolean_type_node, start_tree,
+					      length_tree));
+
+  int code = (array_type->length() != NULL
+	      ? (this->end_ == NULL
+		 ? RUNTIME_ERROR_ARRAY_INDEX_OUT_OF_BOUNDS
+		 : RUNTIME_ERROR_ARRAY_SLICE_OUT_OF_BOUNDS)
+	      : (this->end_ == NULL
+		 ? RUNTIME_ERROR_SLICE_INDEX_OUT_OF_BOUNDS
+		 : RUNTIME_ERROR_SLICE_SLICE_OUT_OF_BOUNDS));
+  tree crash = Gogo::runtime_error(code, loc);
+
+  if (this->end_ == NULL)
+    {
+      // Simple array indexing.  This has to return an l-value, so
+      // wrap the index check into START_TREE.
+      start_tree = build2(COMPOUND_EXPR, TREE_TYPE(start_tree),
+			  build3(COND_EXPR, void_type_node,
+				 bad_index, crash, NULL_TREE),
+			  start_tree);
+      start_tree = fold_convert_loc(loc, sizetype, start_tree);
+
+      if (array_type->length() != NULL)
+	{
+	  // Fixed array.
+	  return build4(ARRAY_REF, TREE_TYPE(type_tree), array_tree,
+			start_tree, NULL_TREE, NULL_TREE);
+	}
+      else
+	{
+	  // Open array.
+	  tree values = array_type->value_pointer_tree(gogo, array_tree);
+	  tree element_type_tree = array_type->element_type()->get_tree(gogo);
+	  if (element_type_tree == error_mark_node)
+	    return error_mark_node;
+	  tree element_size = TYPE_SIZE_UNIT(element_type_tree);
+	  tree offset = fold_build2_loc(loc, MULT_EXPR, sizetype,
+					start_tree, element_size);
+	  tree ptr = fold_build2_loc(loc, POINTER_PLUS_EXPR,
+				     TREE_TYPE(values), values, offset);
+	  return build_fold_indirect_ref(ptr);
+	}
+    }
+
+  // Array slice.
+
+  tree capacity_tree = array_type->capacity_tree(gogo, array_tree);
+  if (capacity_tree == error_mark_node)
+    return error_mark_node;
+  capacity_tree = fold_convert_loc(loc, length_type, capacity_tree);
+
+  tree end_tree;
+  if (this->end_->is_nil_expression())
+    end_tree = length_tree;
+  else
+    {
+      end_tree = this->end_->get_tree(context);
+      if (end_tree == error_mark_node)
+	return error_mark_node;
+      if (!DECL_P(end_tree))
+	end_tree = save_expr(end_tree);
+      if (!INTEGRAL_TYPE_P(TREE_TYPE(end_tree)))
+	end_tree = convert_to_integer(length_type, end_tree);
+
+      bad_index = Expression::check_bounds(end_tree, length_type, bad_index,
+					   loc);
+
+      end_tree = fold_convert_loc(loc, length_type, end_tree);
+
+      capacity_tree = save_expr(capacity_tree);
+      tree bad_end = fold_build2_loc(loc, TRUTH_OR_EXPR, boolean_type_node,
+				     fold_build2_loc(loc, LT_EXPR,
+						     boolean_type_node,
+						     end_tree, start_tree),
+				     fold_build2_loc(loc, GT_EXPR,
+						     boolean_type_node,
+						     end_tree, capacity_tree));
+      bad_index = fold_build2_loc(loc, TRUTH_OR_EXPR, boolean_type_node,
+				  bad_index, bad_end);
+    }
+
+  tree element_type_tree = array_type->element_type()->get_tree(gogo);
+  if (element_type_tree == error_mark_node)
+    return error_mark_node;
+  tree element_size = TYPE_SIZE_UNIT(element_type_tree);
+
+  tree offset = fold_build2_loc(loc, MULT_EXPR, sizetype,
+				fold_convert_loc(loc, sizetype, start_tree),
+				element_size);
+
+  tree value_pointer = array_type->value_pointer_tree(gogo, array_tree);
+  if (value_pointer == error_mark_node)
+    return error_mark_node;
+
+  value_pointer = fold_build2_loc(loc, POINTER_PLUS_EXPR,
+				  TREE_TYPE(value_pointer),
+				  value_pointer, offset);
+
+  tree result_length_tree = fold_build2_loc(loc, MINUS_EXPR, length_type,
+					    end_tree, start_tree);
+
+  tree result_capacity_tree = fold_build2_loc(loc, MINUS_EXPR, length_type,
+					      capacity_tree, start_tree);
+
+  tree struct_tree = this->type()->get_tree(gogo);
+  gcc_assert(TREE_CODE(struct_tree) == RECORD_TYPE);
+
+  VEC(constructor_elt,gc)* init = VEC_alloc(constructor_elt, gc, 3);
+
+  constructor_elt* elt = VEC_quick_push(constructor_elt, init, NULL);
+  tree field = TYPE_FIELDS(struct_tree);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__values") == 0);
+  elt->index = field;
+  elt->value = value_pointer;
+
+  elt = VEC_quick_push(constructor_elt, init, NULL);
+  field = DECL_CHAIN(field);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__count") == 0);
+  elt->index = field;
+  elt->value = fold_convert_loc(loc, TREE_TYPE(field), result_length_tree);
+
+  elt = VEC_quick_push(constructor_elt, init, NULL);
+  field = DECL_CHAIN(field);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__capacity") == 0);
+  elt->index = field;
+  elt->value = fold_convert_loc(loc, TREE_TYPE(field), result_capacity_tree);
+
+  tree constructor = build_constructor(struct_tree, init);
+
+  if (TREE_CONSTANT(value_pointer)
+      && TREE_CONSTANT(result_length_tree)
+      && TREE_CONSTANT(result_capacity_tree))
+    TREE_CONSTANT(constructor) = 1;
+
+  return fold_build2_loc(loc, COMPOUND_EXPR, TREE_TYPE(constructor),
+			 build3(COND_EXPR, void_type_node,
+				bad_index, crash, NULL_TREE),
+			 constructor);
+}
+
+// Make an array index expression.  END may be NULL.
+
+Expression*
+Expression::make_array_index(Expression* array, Expression* start,
+			     Expression* end, source_location location)
+{
+  // Taking a slice of a composite literal requires moving the literal
+  // onto the heap.
+  if (end != NULL && array->is_composite_literal())
+    {
+      array = Expression::make_heap_composite(array, location);
+      array = Expression::make_unary(OPERATOR_MULT, array, location);
+    }
+  return new Array_index_expression(array, start, end, location);
+}
+
+// A string index.  This is used for both indexing and slicing.
+
+class String_index_expression : public Expression
+{
+ public:
+  String_index_expression(Expression* string, Expression* start,
+			  Expression* end, source_location location)
+    : Expression(EXPRESSION_STRING_INDEX, location),
+      string_(string), start_(start), end_(end)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse*);
+
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return Expression::make_string_index(this->string_->copy(),
+					 this->start_->copy(),
+					 (this->end_ == NULL
+					  ? NULL
+					  : this->end_->copy()),
+					 this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context*);
+
+ private:
+  // The string we are getting a value from.
+  Expression* string_;
+  // The start or only index.
+  Expression* start_;
+  // The end index of a slice.  This may be NULL for a single index,
+  // or it may be a nil expression for the length of the string.
+  Expression* end_;
+};
+
+// String index traversal.
+
+int
+String_index_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->string_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (Expression::traverse(&this->start_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (this->end_ != NULL)
+    {
+      if (Expression::traverse(&this->end_, traverse) == TRAVERSE_EXIT)
+	return TRAVERSE_EXIT;
+    }
+  return TRAVERSE_CONTINUE;
+}
+
+// Return the type of a string index.
+
+Type*
+String_index_expression::do_type()
+{
+  if (this->end_ == NULL)
+    return Type::lookup_integer_type("uint8");
+  else
+    return this->string_->type();
+}
+
+// Determine the type of a string index.
+
+void
+String_index_expression::do_determine_type(const Type_context*)
+{
+  this->string_->determine_type_no_context();
+  this->start_->determine_type_no_context();
+  if (this->end_ != NULL)
+    this->end_->determine_type_no_context();
+}
+
+// Check types of a string index.
+
+void
+String_index_expression::do_check_types(Gogo*)
+{
+  if (this->start_->type()->integer_type() == NULL)
+    this->report_error(_("index must be integer"));
+  if (this->end_ != NULL
+      && this->end_->type()->integer_type() == NULL
+      && !this->end_->is_nil_expression())
+    this->report_error(_("slice end must be integer"));
+
+  std::string sval;
+  bool sval_valid = this->string_->string_constant_value(&sval);
+
+  mpz_t ival;
+  mpz_init(ival);
+  Type* dummy;
+  if (this->start_->integer_constant_value(true, ival, &dummy))
+    {
+      if (mpz_sgn(ival) < 0
+	  || (sval_valid && mpz_cmp_ui(ival, sval.length()) >= 0))
+	{
+	  error_at(this->start_->location(), "string index out of bounds");
+	  this->set_is_error();
+	}
+    }
+  if (this->end_ != NULL && !this->end_->is_nil_expression())
+    {
+      if (this->end_->integer_constant_value(true, ival, &dummy))
+	{
+	  if (mpz_sgn(ival) < 0
+	      || (sval_valid && mpz_cmp_ui(ival, sval.length()) > 0))
+	    {
+	      error_at(this->end_->location(), "string index out of bounds");
+	      this->set_is_error();
+	    }
+	}
+    }
+  mpz_clear(ival);
+}
+
+// Get a tree for a string index.
+
+tree
+String_index_expression::do_get_tree(Translate_context* context)
+{
+  source_location loc = this->location();
+
+  tree string_tree = this->string_->get_tree(context);
+  if (string_tree == error_mark_node)
+    return error_mark_node;
+
+  if (this->string_->type()->points_to() != NULL)
+    string_tree = build_fold_indirect_ref(string_tree);
+  if (!DECL_P(string_tree))
+    string_tree = save_expr(string_tree);
+  tree string_type = TREE_TYPE(string_tree);
+
+  tree length_tree = String_type::length_tree(context->gogo(), string_tree);
+  length_tree = save_expr(length_tree);
+  tree length_type = TREE_TYPE(length_tree);
+
+  tree bad_index = boolean_false_node;
+
+  tree start_tree = this->start_->get_tree(context);
+  if (start_tree == error_mark_node)
+    return error_mark_node;
+  if (!DECL_P(start_tree))
+    start_tree = save_expr(start_tree);
+  if (!INTEGRAL_TYPE_P(TREE_TYPE(start_tree)))
+    start_tree = convert_to_integer(length_type, start_tree);
+
+  bad_index = Expression::check_bounds(start_tree, length_type, bad_index,
+				       loc);
+
+  start_tree = fold_convert_loc(loc, length_type, start_tree);
+
+  int code = (this->end_ == NULL
+	      ? RUNTIME_ERROR_STRING_INDEX_OUT_OF_BOUNDS
+	      : RUNTIME_ERROR_STRING_SLICE_OUT_OF_BOUNDS);
+  tree crash = Gogo::runtime_error(code, loc);
+
+  if (this->end_ == NULL)
+    {
+      bad_index = fold_build2_loc(loc, TRUTH_OR_EXPR, boolean_type_node,
+				  bad_index,
+				  fold_build2_loc(loc, GE_EXPR,
+						  boolean_type_node,
+						  start_tree, length_tree));
+
+      tree bytes_tree = String_type::bytes_tree(context->gogo(), string_tree);
+      tree ptr = fold_build2_loc(loc, POINTER_PLUS_EXPR, TREE_TYPE(bytes_tree),
+				 bytes_tree,
+				 fold_convert_loc(loc, sizetype, start_tree));
+      tree index = build_fold_indirect_ref_loc(loc, ptr);
+
+      return build2(COMPOUND_EXPR, TREE_TYPE(index),
+		    build3(COND_EXPR, void_type_node,
+			   bad_index, crash, NULL_TREE),
+		    index);
+    }
+  else
+    {
+      tree end_tree;
+      if (this->end_->is_nil_expression())
+	end_tree = build_int_cst(length_type, -1);
+      else
+	{
+	  end_tree = this->end_->get_tree(context);
+	  if (end_tree == error_mark_node)
+	    return error_mark_node;
+	  if (!DECL_P(end_tree))
+	    end_tree = save_expr(end_tree);
+	  if (!INTEGRAL_TYPE_P(TREE_TYPE(end_tree)))
+	    end_tree = convert_to_integer(length_type, end_tree);
+
+	  bad_index = Expression::check_bounds(end_tree, length_type,
+					       bad_index, loc);
+
+	  end_tree = fold_convert_loc(loc, length_type, end_tree);
+	}
+
+      static tree strslice_fndecl;
+      tree ret = Gogo::call_builtin(&strslice_fndecl,
+				    loc,
+				    "__go_string_slice",
+				    3,
+				    string_type,
+				    string_type,
+				    string_tree,
+				    length_type,
+				    start_tree,
+				    length_type,
+				    end_tree);
+      if (ret == error_mark_node)
+	return error_mark_node;
+      // This will panic if the bounds are out of range for the
+      // string.
+      TREE_NOTHROW(strslice_fndecl) = 0;
+
+      if (bad_index == boolean_false_node)
+	return ret;
+      else
+	return build2(COMPOUND_EXPR, TREE_TYPE(ret),
+		      build3(COND_EXPR, void_type_node,
+			     bad_index, crash, NULL_TREE),
+		      ret);
+    }
+}
+
+// Make a string index expression.  END may be NULL.
+
+Expression*
+Expression::make_string_index(Expression* string, Expression* start,
+			      Expression* end, source_location location)
+{
+  return new String_index_expression(string, start, end, location);
+}
+
+// Class Map_index.
+
+// Get the type of the map.
+
+Map_type*
+Map_index_expression::get_map_type() const
+{
+  Map_type* mt = this->map_->type()->deref()->map_type();
+  if (mt == NULL)
+    gcc_assert(saw_errors());
+  return mt;
+}
+
+// Map index traversal.
+
+int
+Map_index_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->map_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return Expression::traverse(&this->index_, traverse);
+}
+
+// Return the type of a map index.
+
+Type*
+Map_index_expression::do_type()
+{
+  Map_type* mt = this->get_map_type();
+  if (mt == NULL)
+    return Type::make_error_type();
+  Type* type = mt->val_type();
+  // If this map index is in a tuple assignment, we actually return a
+  // pointer to the value type.  Tuple_map_assignment_statement is
+  // responsible for handling this correctly.  We need to get the type
+  // right in case this gets assigned to a temporary variable.
+  if (this->is_in_tuple_assignment_)
+    type = Type::make_pointer_type(type);
+  return type;
+}
+
+// Fix the type of a map index.
+
+void
+Map_index_expression::do_determine_type(const Type_context*)
+{
+  this->map_->determine_type_no_context();
+  Map_type* mt = this->get_map_type();
+  Type* key_type = mt == NULL ? NULL : mt->key_type();
+  Type_context subcontext(key_type, false);
+  this->index_->determine_type(&subcontext);
+}
+
+// Check types of a map index.
+
+void
+Map_index_expression::do_check_types(Gogo*)
+{
+  std::string reason;
+  Map_type* mt = this->get_map_type();
+  if (mt == NULL)
+    return;
+  if (!Type::are_assignable(mt->key_type(), this->index_->type(), &reason))
+    {
+      if (reason.empty())
+	this->report_error(_("incompatible type for map index"));
+      else
+	{
+	  error_at(this->location(), "incompatible type for map index (%s)",
+		   reason.c_str());
+	  this->set_is_error();
+	}
+    }
+}
+
+// Get a tree for a map index.
+
+tree
+Map_index_expression::do_get_tree(Translate_context* context)
+{
+  Map_type* type = this->get_map_type();
+  if (type == NULL)
+    return error_mark_node;
+
+  tree valptr = this->get_value_pointer(context, this->is_lvalue_);
+  if (valptr == error_mark_node)
+    return error_mark_node;
+  valptr = save_expr(valptr);
+
+  tree val_type_tree = TREE_TYPE(TREE_TYPE(valptr));
+
+  if (this->is_lvalue_)
+    return build_fold_indirect_ref(valptr);
+  else if (this->is_in_tuple_assignment_)
+    {
+      // Tuple_map_assignment_statement is responsible for using this
+      // appropriately.
+      return valptr;
+    }
+  else
+    {
+      return fold_build3(COND_EXPR, val_type_tree,
+			 fold_build2(EQ_EXPR, boolean_type_node, valptr,
+				     fold_convert(TREE_TYPE(valptr),
+						  null_pointer_node)),
+			 type->val_type()->get_init_tree(context->gogo(),
+							 false),
+			 build_fold_indirect_ref(valptr));
+    }
+}
+
+// Get a tree for the map index.  This returns a tree which evaluates
+// to a pointer to a value.  The pointer will be NULL if the key is
+// not in the map.
+
+tree
+Map_index_expression::get_value_pointer(Translate_context* context,
+					bool insert)
+{
+  Map_type* type = this->get_map_type();
+  if (type == NULL)
+    return error_mark_node;
+
+  tree map_tree = this->map_->get_tree(context);
+  tree index_tree = this->index_->get_tree(context);
+  index_tree = Expression::convert_for_assignment(context, type->key_type(),
+						  this->index_->type(),
+						  index_tree,
+						  this->location());
+  if (map_tree == error_mark_node || index_tree == error_mark_node)
+    return error_mark_node;
+
+  if (this->map_->type()->points_to() != NULL)
+    map_tree = build_fold_indirect_ref(map_tree);
+
+  // We need to pass in a pointer to the key, so stuff it into a
+  // variable.
+  tree tmp;
+  tree make_tmp;
+  if (current_function_decl != NULL)
+    {
+      tmp = create_tmp_var(TREE_TYPE(index_tree), get_name(index_tree));
+      DECL_IGNORED_P(tmp) = 0;
+      DECL_INITIAL(tmp) = index_tree;
+      make_tmp = build1(DECL_EXPR, void_type_node, tmp);
+      TREE_ADDRESSABLE(tmp) = 1;
+    }
+  else
+    {
+      tmp = build_decl(this->location(), VAR_DECL, create_tmp_var_name("M"),
+		       TREE_TYPE(index_tree));
+      DECL_EXTERNAL(tmp) = 0;
+      TREE_PUBLIC(tmp) = 0;
+      TREE_STATIC(tmp) = 1;
+      DECL_ARTIFICIAL(tmp) = 1;
+      if (!TREE_CONSTANT(index_tree))
+	make_tmp = fold_build2_loc(this->location(), INIT_EXPR, void_type_node,
+				   tmp, index_tree);
+      else
+	{
+	  TREE_READONLY(tmp) = 1;
+	  TREE_CONSTANT(tmp) = 1;
+	  DECL_INITIAL(tmp) = index_tree;
+	  make_tmp = NULL_TREE;
+	}
+      rest_of_decl_compilation(tmp, 1, 0);
+    }
+  tree tmpref = fold_convert_loc(this->location(), const_ptr_type_node,
+				 build_fold_addr_expr_loc(this->location(),
+							  tmp));
+
+  static tree map_index_fndecl;
+  tree call = Gogo::call_builtin(&map_index_fndecl,
+				 this->location(),
+				 "__go_map_index",
+				 3,
+				 const_ptr_type_node,
+				 TREE_TYPE(map_tree),
+				 map_tree,
+				 const_ptr_type_node,
+				 tmpref,
+				 boolean_type_node,
+				 (insert
+				  ? boolean_true_node
+				  : boolean_false_node));
+  if (call == error_mark_node)
+    return error_mark_node;
+  // This can panic on a map of interface type if the interface holds
+  // an uncomparable or unhashable type.
+  TREE_NOTHROW(map_index_fndecl) = 0;
+
+  tree val_type_tree = type->val_type()->get_tree(context->gogo());
+  if (val_type_tree == error_mark_node)
+    return error_mark_node;
+  tree ptr_val_type_tree = build_pointer_type(val_type_tree);
+
+  tree ret = fold_convert_loc(this->location(), ptr_val_type_tree, call);
+  if (make_tmp != NULL_TREE)
+    ret = build2(COMPOUND_EXPR, ptr_val_type_tree, make_tmp, ret);
+  return ret;
+}
+
+// Make a map index expression.
+
+Map_index_expression*
+Expression::make_map_index(Expression* map, Expression* index,
+			   source_location location)
+{
+  return new Map_index_expression(map, index, location);
+}
+
+// Class Field_reference_expression.
+
+// Return the type of a field reference.
+
+Type*
+Field_reference_expression::do_type()
+{
+  Type* type = this->expr_->type();
+  if (type->is_error_type())
+    return type;
+  Struct_type* struct_type = type->struct_type();
+  gcc_assert(struct_type != NULL);
+  return struct_type->field(this->field_index_)->type();
+}
+
+// Check the types for a field reference.
+
+void
+Field_reference_expression::do_check_types(Gogo*)
+{
+  Type* type = this->expr_->type();
+  if (type->is_error_type())
+    return;
+  Struct_type* struct_type = type->struct_type();
+  gcc_assert(struct_type != NULL);
+  gcc_assert(struct_type->field(this->field_index_) != NULL);
+}
+
+// Get a tree for a field reference.
+
+tree
+Field_reference_expression::do_get_tree(Translate_context* context)
+{
+  tree struct_tree = this->expr_->get_tree(context);
+  if (struct_tree == error_mark_node
+      || TREE_TYPE(struct_tree) == error_mark_node)
+    return error_mark_node;
+  gcc_assert(TREE_CODE(TREE_TYPE(struct_tree)) == RECORD_TYPE);
+  tree field = TYPE_FIELDS(TREE_TYPE(struct_tree));
+  if (field == NULL_TREE)
+    {
+      // This can happen for a type which refers to itself indirectly
+      // and then turns out to be erroneous.
+      gcc_assert(saw_errors());
+      return error_mark_node;
+    }
+  for (unsigned int i = this->field_index_; i > 0; --i)
+    {
+      field = DECL_CHAIN(field);
+      gcc_assert(field != NULL_TREE);
+    }
+  if (TREE_TYPE(field) == error_mark_node)
+    return error_mark_node;
+  return build3(COMPONENT_REF, TREE_TYPE(field), struct_tree, field,
+		NULL_TREE);
+}
+
+// Make a reference to a qualified identifier in an expression.
+
+Field_reference_expression*
+Expression::make_field_reference(Expression* expr, unsigned int field_index,
+				 source_location location)
+{
+  return new Field_reference_expression(expr, field_index, location);
+}
+
+// Class Interface_field_reference_expression.
+
+// Return a tree for the pointer to the function to call.
+
+tree
+Interface_field_reference_expression::get_function_tree(Translate_context*,
+							tree expr)
+{
+  if (this->expr_->type()->points_to() != NULL)
+    expr = build_fold_indirect_ref(expr);
+
+  tree expr_type = TREE_TYPE(expr);
+  gcc_assert(TREE_CODE(expr_type) == RECORD_TYPE);
+
+  tree field = TYPE_FIELDS(expr_type);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__methods") == 0);
+
+  tree table = build3(COMPONENT_REF, TREE_TYPE(field), expr, field, NULL_TREE);
+  gcc_assert(POINTER_TYPE_P(TREE_TYPE(table)));
+
+  table = build_fold_indirect_ref(table);
+  gcc_assert(TREE_CODE(TREE_TYPE(table)) == RECORD_TYPE);
+
+  std::string name = Gogo::unpack_hidden_name(this->name_);
+  for (field = DECL_CHAIN(TYPE_FIELDS(TREE_TYPE(table)));
+       field != NULL_TREE;
+       field = DECL_CHAIN(field))
+    {
+      if (name == IDENTIFIER_POINTER(DECL_NAME(field)))
+	break;
+    }
+  gcc_assert(field != NULL_TREE);
+
+  return build3(COMPONENT_REF, TREE_TYPE(field), table, field, NULL_TREE);
+}
+
+// Return a tree for the first argument to pass to the interface
+// function.
+
+tree
+Interface_field_reference_expression::get_underlying_object_tree(
+    Translate_context*,
+    tree expr)
+{
+  if (this->expr_->type()->points_to() != NULL)
+    expr = build_fold_indirect_ref(expr);
+
+  tree expr_type = TREE_TYPE(expr);
+  gcc_assert(TREE_CODE(expr_type) == RECORD_TYPE);
+
+  tree field = DECL_CHAIN(TYPE_FIELDS(expr_type));
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__object") == 0);
+
+  return build3(COMPONENT_REF, TREE_TYPE(field), expr, field, NULL_TREE);
+}
+
+// Traversal.
+
+int
+Interface_field_reference_expression::do_traverse(Traverse* traverse)
+{
+  return Expression::traverse(&this->expr_, traverse);
+}
+
+// Return the type of an interface field reference.
+
+Type*
+Interface_field_reference_expression::do_type()
+{
+  Type* expr_type = this->expr_->type();
+
+  Type* points_to = expr_type->points_to();
+  if (points_to != NULL)
+    expr_type = points_to;
+
+  Interface_type* interface_type = expr_type->interface_type();
+  if (interface_type == NULL)
+    return Type::make_error_type();
+
+  const Typed_identifier* method = interface_type->find_method(this->name_);
+  if (method == NULL)
+    return Type::make_error_type();
+
+  return method->type();
+}
+
+// Determine types.
+
+void
+Interface_field_reference_expression::do_determine_type(const Type_context*)
+{
+  this->expr_->determine_type_no_context();
+}
+
+// Check the types for an interface field reference.
+
+void
+Interface_field_reference_expression::do_check_types(Gogo*)
+{
+  Type* type = this->expr_->type();
+
+  Type* points_to = type->points_to();
+  if (points_to != NULL)
+    type = points_to;
+
+  Interface_type* interface_type = type->interface_type();
+  if (interface_type == NULL)
+    this->report_error(_("expected interface or pointer to interface"));
+  else
+    {
+      const Typed_identifier* method =
+	interface_type->find_method(this->name_);
+      if (method == NULL)
+	{
+	  error_at(this->location(), "method %qs not in interface",
+		   Gogo::message_name(this->name_).c_str());
+	  this->set_is_error();
+	}
+    }
+}
+
+// Get a tree for a reference to a field in an interface.  There is no
+// standard tree type representation for this: it's a function
+// attached to its first argument, like a Bound_method_expression.
+// The only places it may currently be used are in a Call_expression
+// or a Go_statement, which will take it apart directly.  So this has
+// nothing to do at present.
+
+tree
+Interface_field_reference_expression::do_get_tree(Translate_context*)
+{
+  gcc_unreachable();
+}
+
+// Make a reference to a field in an interface.
+
+Expression*
+Expression::make_interface_field_reference(Expression* expr,
+					   const std::string& field,
+					   source_location location)
+{
+  return new Interface_field_reference_expression(expr, field, location);
+}
+
+// A general selector.  This is a Parser_expression for LEFT.NAME.  It
+// is lowered after we know the type of the left hand side.
+
+class Selector_expression : public Parser_expression
+{
+ public:
+  Selector_expression(Expression* left, const std::string& name,
+		      source_location location)
+    : Parser_expression(EXPRESSION_SELECTOR, location),
+      left_(left), name_(name)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse)
+  { return Expression::traverse(&this->left_, traverse); }
+
+  Expression*
+  do_lower(Gogo*, Named_object*, int);
+
+  Expression*
+  do_copy()
+  {
+    return new Selector_expression(this->left_->copy(), this->name_,
+				   this->location());
+  }
+
+ private:
+  Expression*
+  lower_method_expression(Gogo*);
+
+  // The expression on the left hand side.
+  Expression* left_;
+  // The name on the right hand side.
+  std::string name_;
+};
+
+// Lower a selector expression once we know the real type of the left
+// hand side.
+
+Expression*
+Selector_expression::do_lower(Gogo* gogo, Named_object*, int)
+{
+  Expression* left = this->left_;
+  if (left->is_type_expression())
+    return this->lower_method_expression(gogo);
+  return Type::bind_field_or_method(gogo, left->type(), left, this->name_,
+				    this->location());
+}
+
+// Lower a method expression T.M or (*T).M.  We turn this into a
+// function literal.
+
+Expression*
+Selector_expression::lower_method_expression(Gogo* gogo)
+{
+  source_location location = this->location();
+  Type* type = this->left_->type();
+  const std::string& name(this->name_);
+
+  bool is_pointer;
+  if (type->points_to() == NULL)
+    is_pointer = false;
+  else
+    {
+      is_pointer = true;
+      type = type->points_to();
+    }
+  Named_type* nt = type->named_type();
+  if (nt == NULL)
+    {
+      error_at(location,
+	       ("method expression requires named type or "
+		"pointer to named type"));
+      return Expression::make_error(location);
+    }
+
+  bool is_ambiguous;
+  Method* method = nt->method_function(name, &is_ambiguous);
+  if (method == NULL)
+    {
+      if (!is_ambiguous)
+	error_at(location, "type %<%s%> has no method %<%s%>",
+		 nt->message_name().c_str(),
+		 Gogo::message_name(name).c_str());
+      else
+	error_at(location, "method %<%s%> is ambiguous in type %<%s%>",
+		 Gogo::message_name(name).c_str(),
+		 nt->message_name().c_str());
+      return Expression::make_error(location);
+    }
+
+  if (!is_pointer && !method->is_value_method())
+    {
+      error_at(location, "method requires pointer (use %<(*%s).%s)%>",
+	       nt->message_name().c_str(),
+	       Gogo::message_name(name).c_str());
+      return Expression::make_error(location);
+    }
+
+  // Build a new function type in which the receiver becomes the first
+  // argument.
+  Function_type* method_type = method->type();
+  gcc_assert(method_type->is_method());
+
+  const char* const receiver_name = "$this";
+  Typed_identifier_list* parameters = new Typed_identifier_list();
+  parameters->push_back(Typed_identifier(receiver_name, this->left_->type(),
+					 location));
+
+  const Typed_identifier_list* method_parameters = method_type->parameters();
+  if (method_parameters != NULL)
+    {
+      for (Typed_identifier_list::const_iterator p = method_parameters->begin();
+	   p != method_parameters->end();
+	   ++p)
+	parameters->push_back(*p);
+    }
+
+  const Typed_identifier_list* method_results = method_type->results();
+  Typed_identifier_list* results;
+  if (method_results == NULL)
+    results = NULL;
+  else
+    {
+      results = new Typed_identifier_list();
+      for (Typed_identifier_list::const_iterator p = method_results->begin();
+	   p != method_results->end();
+	   ++p)
+	results->push_back(*p);
+    }
+  
+  Function_type* fntype = Type::make_function_type(NULL, parameters, results,
+						   location);
+  if (method_type->is_varargs())
+    fntype->set_is_varargs();
+
+  // We generate methods which always takes a pointer to the receiver
+  // as their first argument.  If this is for a pointer type, we can
+  // simply reuse the existing function.  We use an internal hack to
+  // get the right type.
+
+  if (is_pointer)
+    {
+      Named_object* mno = (method->needs_stub_method()
+			   ? method->stub_object()
+			   : method->named_object());
+      Expression* f = Expression::make_func_reference(mno, NULL, location);
+      f = Expression::make_cast(fntype, f, location);
+      Type_conversion_expression* tce =
+	static_cast<Type_conversion_expression*>(f);
+      tce->set_may_convert_function_types();
+      return f;
+    }
+
+  Named_object* no = gogo->start_function(Gogo::thunk_name(), fntype, false,
+					  location);
+
+  Named_object* vno = gogo->lookup(receiver_name, NULL);
+  gcc_assert(vno != NULL);
+  Expression* ve = Expression::make_var_reference(vno, location);
+  Expression* bm = Type::bind_field_or_method(gogo, nt, ve, name, location);
+
+  // Even though we found the method above, if it has an error type we
+  // may see an error here.
+  if (bm->is_error_expression())
+    {
+      gogo->finish_function(location);
+      return bm;
+    }
+
+  Expression_list* args;
+  if (method_parameters == NULL)
+    args = NULL;
+  else
+    {
+      args = new Expression_list();
+      for (Typed_identifier_list::const_iterator p = method_parameters->begin();
+	   p != method_parameters->end();
+	   ++p)
+	{
+	  vno = gogo->lookup(p->name(), NULL);
+	  gcc_assert(vno != NULL);
+	  args->push_back(Expression::make_var_reference(vno, location));
+	}
+    }
+
+  Call_expression* call = Expression::make_call(bm, args,
+						method_type->is_varargs(),
+						location);
+
+  size_t count = call->result_count();
+  Statement* s;
+  if (count == 0)
+    s = Statement::make_statement(call);
+  else
+    {
+      Expression_list* retvals = new Expression_list();
+      if (count <= 1)
+	retvals->push_back(call);
+      else
+	{
+	  for (size_t i = 0; i < count; ++i)
+	    retvals->push_back(Expression::make_call_result(call, i));
+	}
+      s = Statement::make_return_statement(no->func_value()->type()->results(),
+					   retvals, location);
+    }
+  gogo->add_statement(s);
+
+  gogo->finish_function(location);
+
+  return Expression::make_func_reference(no, NULL, location);
+}
+
+// Make a selector expression.
+
+Expression*
+Expression::make_selector(Expression* left, const std::string& name,
+			  source_location location)
+{
+  return new Selector_expression(left, name, location);
+}
+
+// Implement the builtin function new.
+
+class Allocation_expression : public Expression
+{
+ public:
+  Allocation_expression(Type* type, source_location location)
+    : Expression(EXPRESSION_ALLOCATION, location),
+      type_(type)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse)
+  { return Type::traverse(this->type_, traverse); }
+
+  Type*
+  do_type()
+  { return Type::make_pointer_type(this->type_); }
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  { return new Allocation_expression(this->type_, this->location()); }
+
+  tree
+  do_get_tree(Translate_context*);
+
+ private:
+  // The type we are allocating.
+  Type* type_;
+};
+
+// Check the type of an allocation expression.
+
+void
+Allocation_expression::do_check_types(Gogo*)
+{
+  if (this->type_->function_type() != NULL)
+    this->report_error(_("invalid new of function type"));
+}
+
+// Return a tree for an allocation expression.
+
+tree
+Allocation_expression::do_get_tree(Translate_context* context)
+{
+  tree type_tree = this->type_->get_tree(context->gogo());
+  if (type_tree == error_mark_node)
+    return error_mark_node;
+  tree size_tree = TYPE_SIZE_UNIT(type_tree);
+  tree space = context->gogo()->allocate_memory(this->type_, size_tree,
+						this->location());
+  if (space == error_mark_node)
+    return error_mark_node;
+  return fold_convert(build_pointer_type(type_tree), space);
+}
+
+// Make an allocation expression.
+
+Expression*
+Expression::make_allocation(Type* type, source_location location)
+{
+  return new Allocation_expression(type, location);
+}
+
+// Implement the builtin function make.
+
+class Make_expression : public Expression
+{
+ public:
+  Make_expression(Type* type, Expression_list* args, source_location location)
+    : Expression(EXPRESSION_MAKE, location),
+      type_(type), args_(args)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse);
+
+  Type*
+  do_type()
+  { return this->type_; }
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return new Make_expression(this->type_, this->args_->copy(),
+			       this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context*);
+
+ private:
+  // The type we are making.
+  Type* type_;
+  // The arguments to pass to the make routine.
+  Expression_list* args_;
+};
+
+// Traversal.
+
+int
+Make_expression::do_traverse(Traverse* traverse)
+{
+  if (this->args_ != NULL
+      && this->args_->traverse(traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (Type::traverse(this->type_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return TRAVERSE_CONTINUE;
+}
+
+// Set types of arguments.
+
+void
+Make_expression::do_determine_type(const Type_context*)
+{
+  if (this->args_ != NULL)
+    {
+      Type_context context(Type::lookup_integer_type("int"), false);
+      for (Expression_list::const_iterator pe = this->args_->begin();
+	   pe != this->args_->end();
+	   ++pe)
+	(*pe)->determine_type(&context);
+    }
+}
+
+// Check types for a make expression.
+
+void
+Make_expression::do_check_types(Gogo*)
+{
+  if (this->type_->channel_type() == NULL
+      && this->type_->map_type() == NULL
+      && (this->type_->array_type() == NULL
+	  || this->type_->array_type()->length() != NULL))
+    this->report_error(_("invalid type for make function"));
+  else if (!this->type_->check_make_expression(this->args_, this->location()))
+    this->set_is_error();
+}
+
+// Return a tree for a make expression.
+
+tree
+Make_expression::do_get_tree(Translate_context* context)
+{
+  return this->type_->make_expression_tree(context, this->args_,
+					   this->location());
+}
+
+// Make a make expression.
+
+Expression*
+Expression::make_make(Type* type, Expression_list* args,
+		      source_location location)
+{
+  return new Make_expression(type, args, location);
+}
+
+// Construct a struct.
+
+class Struct_construction_expression : public Expression
+{
+ public:
+  Struct_construction_expression(Type* type, Expression_list* vals,
+				 source_location location)
+    : Expression(EXPRESSION_STRUCT_CONSTRUCTION, location),
+      type_(type), vals_(vals)
+  { }
+
+  // Return whether this is a constant initializer.
+  bool
+  is_constant_struct() const;
+
+ protected:
+  int
+  do_traverse(Traverse* traverse);
+
+  Type*
+  do_type()
+  { return this->type_; }
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return new Struct_construction_expression(this->type_, this->vals_->copy(),
+					      this->location());
+  }
+
+  bool
+  do_is_addressable() const
+  { return true; }
+
+  tree
+  do_get_tree(Translate_context*);
+
+  void
+  do_export(Export*) const;
+
+ private:
+  // The type of the struct to construct.
+  Type* type_;
+  // The list of values, in order of the fields in the struct.  A NULL
+  // entry means that the field should be zero-initialized.
+  Expression_list* vals_;
+};
+
+// Traversal.
+
+int
+Struct_construction_expression::do_traverse(Traverse* traverse)
+{
+  if (this->vals_ != NULL
+      && this->vals_->traverse(traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (Type::traverse(this->type_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return TRAVERSE_CONTINUE;
+}
+
+// Return whether this is a constant initializer.
+
+bool
+Struct_construction_expression::is_constant_struct() const
+{
+  if (this->vals_ == NULL)
+    return true;
+  for (Expression_list::const_iterator pv = this->vals_->begin();
+       pv != this->vals_->end();
+       ++pv)
+    {
+      if (*pv != NULL
+	  && !(*pv)->is_constant()
+	  && (!(*pv)->is_composite_literal()
+	      || (*pv)->is_nonconstant_composite_literal()))
+	return false;
+    }
+
+  const Struct_field_list* fields = this->type_->struct_type()->fields();
+  for (Struct_field_list::const_iterator pf = fields->begin();
+       pf != fields->end();
+       ++pf)
+    {
+      // There are no constant constructors for interfaces.
+      if (pf->type()->interface_type() != NULL)
+	return false;
+    }
+
+  return true;
+}
+
+// Final type determination.
+
+void
+Struct_construction_expression::do_determine_type(const Type_context*)
+{
+  if (this->vals_ == NULL)
+    return;
+  const Struct_field_list* fields = this->type_->struct_type()->fields();
+  Expression_list::const_iterator pv = this->vals_->begin();
+  for (Struct_field_list::const_iterator pf = fields->begin();
+       pf != fields->end();
+       ++pf, ++pv)
+    {
+      if (pv == this->vals_->end())
+	return;
+      if (*pv != NULL)
+	{
+	  Type_context subcontext(pf->type(), false);
+	  (*pv)->determine_type(&subcontext);
+	}
+    }
+  // Extra values are an error we will report elsewhere; we still want
+  // to determine the type to avoid knockon errors.
+  for (; pv != this->vals_->end(); ++pv)
+    (*pv)->determine_type_no_context();
+}
+
+// Check types.
+
+void
+Struct_construction_expression::do_check_types(Gogo*)
+{
+  if (this->vals_ == NULL)
+    return;
+
+  Struct_type* st = this->type_->struct_type();
+  if (this->vals_->size() > st->field_count())
+    {
+      this->report_error(_("too many expressions for struct"));
+      return;
+    }
+
+  const Struct_field_list* fields = st->fields();
+  Expression_list::const_iterator pv = this->vals_->begin();
+  int i = 0;
+  for (Struct_field_list::const_iterator pf = fields->begin();
+       pf != fields->end();
+       ++pf, ++pv, ++i)
+    {
+      if (pv == this->vals_->end())
+	{
+	  this->report_error(_("too few expressions for struct"));
+	  break;
+	}
+
+      if (*pv == NULL)
+	continue;
+
+      std::string reason;
+      if (!Type::are_assignable(pf->type(), (*pv)->type(), &reason))
+	{
+	  if (reason.empty())
+	    error_at((*pv)->location(),
+		     "incompatible type for field %d in struct construction",
+		     i + 1);
+	  else
+	    error_at((*pv)->location(),
+		     ("incompatible type for field %d in "
+		      "struct construction (%s)"),
+		     i + 1, reason.c_str());
+	  this->set_is_error();
+	}
+    }
+  gcc_assert(pv == this->vals_->end());
+}
+
+// Return a tree for constructing a struct.
+
+tree
+Struct_construction_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+
+  if (this->vals_ == NULL)
+    return this->type_->get_init_tree(gogo, false);
+
+  tree type_tree = this->type_->get_tree(gogo);
+  if (type_tree == error_mark_node)
+    return error_mark_node;
+  gcc_assert(TREE_CODE(type_tree) == RECORD_TYPE);
+
+  bool is_constant = true;
+  const Struct_field_list* fields = this->type_->struct_type()->fields();
+  VEC(constructor_elt,gc)* elts = VEC_alloc(constructor_elt, gc,
+					    fields->size());
+  Struct_field_list::const_iterator pf = fields->begin();
+  Expression_list::const_iterator pv = this->vals_->begin();
+  for (tree field = TYPE_FIELDS(type_tree);
+       field != NULL_TREE;
+       field = DECL_CHAIN(field), ++pf)
+    {
+      gcc_assert(pf != fields->end());
+
+      tree val;
+      if (pv == this->vals_->end())
+	val = pf->type()->get_init_tree(gogo, false);
+      else if (*pv == NULL)
+	{
+	  val = pf->type()->get_init_tree(gogo, false);
+	  ++pv;
+	}
+      else
+	{
+	  val = Expression::convert_for_assignment(context, pf->type(),
+						   (*pv)->type(),
+						   (*pv)->get_tree(context),
+						   this->location());
+	  ++pv;
+	}
+
+      if (val == error_mark_node || TREE_TYPE(val) == error_mark_node)
+	return error_mark_node;
+
+      constructor_elt* elt = VEC_quick_push(constructor_elt, elts, NULL);
+      elt->index = field;
+      elt->value = val;
+      if (!TREE_CONSTANT(val))
+	is_constant = false;
+    }
+  gcc_assert(pf == fields->end());
+
+  tree ret = build_constructor(type_tree, elts);
+  if (is_constant)
+    TREE_CONSTANT(ret) = 1;
+  return ret;
+}
+
+// Export a struct construction.
+
+void
+Struct_construction_expression::do_export(Export* exp) const
+{
+  exp->write_c_string("convert(");
+  exp->write_type(this->type_);
+  for (Expression_list::const_iterator pv = this->vals_->begin();
+       pv != this->vals_->end();
+       ++pv)
+    {
+      exp->write_c_string(", ");
+      if (*pv != NULL)
+	(*pv)->export_expression(exp);
+    }
+  exp->write_c_string(")");
+}
+
+// Make a struct composite literal.  This used by the thunk code.
+
+Expression*
+Expression::make_struct_composite_literal(Type* type, Expression_list* vals,
+					  source_location location)
+{
+  gcc_assert(type->struct_type() != NULL);
+  return new Struct_construction_expression(type, vals, location);
+}
+
+// Construct an array.  This class is not used directly; instead we
+// use the child classes, Fixed_array_construction_expression and
+// Open_array_construction_expression.
+
+class Array_construction_expression : public Expression
+{
+ protected:
+  Array_construction_expression(Expression_classification classification,
+				Type* type, Expression_list* vals,
+				source_location location)
+    : Expression(classification, location),
+      type_(type), vals_(vals)
+  { }
+
+ public:
+  // Return whether this is a constant initializer.
+  bool
+  is_constant_array() const;
+
+  // Return the number of elements.
+  size_t
+  element_count() const
+  { return this->vals_ == NULL ? 0 : this->vals_->size(); }
+
+protected:
+  int
+  do_traverse(Traverse* traverse);
+
+  Type*
+  do_type()
+  { return this->type_; }
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  bool
+  do_is_addressable() const
+  { return true; }
+
+  void
+  do_export(Export*) const;
+
+  // The list of values.
+  Expression_list*
+  vals()
+  { return this->vals_; }
+
+  // Get a constructor tree for the array values.
+  tree
+  get_constructor_tree(Translate_context* context, tree type_tree);
+
+ private:
+  // The type of the array to construct.
+  Type* type_;
+  // The list of values.
+  Expression_list* vals_;
+};
+
+// Traversal.
+
+int
+Array_construction_expression::do_traverse(Traverse* traverse)
+{
+  if (this->vals_ != NULL
+      && this->vals_->traverse(traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (Type::traverse(this->type_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return TRAVERSE_CONTINUE;
+}
+
+// Return whether this is a constant initializer.
+
+bool
+Array_construction_expression::is_constant_array() const
+{
+  if (this->vals_ == NULL)
+    return true;
+
+  // There are no constant constructors for interfaces.
+  if (this->type_->array_type()->element_type()->interface_type() != NULL)
+    return false;
+
+  for (Expression_list::const_iterator pv = this->vals_->begin();
+       pv != this->vals_->end();
+       ++pv)
+    {
+      if (*pv != NULL
+	  && !(*pv)->is_constant()
+	  && (!(*pv)->is_composite_literal()
+	      || (*pv)->is_nonconstant_composite_literal()))
+	return false;
+    }
+  return true;
+}
+
+// Final type determination.
+
+void
+Array_construction_expression::do_determine_type(const Type_context*)
+{
+  if (this->vals_ == NULL)
+    return;
+  Type_context subcontext(this->type_->array_type()->element_type(), false);
+  for (Expression_list::const_iterator pv = this->vals_->begin();
+       pv != this->vals_->end();
+       ++pv)
+    {
+      if (*pv != NULL)
+	(*pv)->determine_type(&subcontext);
+    }
+}
+
+// Check types.
+
+void
+Array_construction_expression::do_check_types(Gogo*)
+{
+  if (this->vals_ == NULL)
+    return;
+
+  Array_type* at = this->type_->array_type();
+  int i = 0;
+  Type* element_type = at->element_type();
+  for (Expression_list::const_iterator pv = this->vals_->begin();
+       pv != this->vals_->end();
+       ++pv, ++i)
+    {
+      if (*pv != NULL
+	  && !Type::are_assignable(element_type, (*pv)->type(), NULL))
+	{
+	  error_at((*pv)->location(),
+		   "incompatible type for element %d in composite literal",
+		   i + 1);
+	  this->set_is_error();
+	}
+    }
+
+  Expression* length = at->length();
+  if (length != NULL)
+    {
+      mpz_t val;
+      mpz_init(val);
+      Type* type;
+      if (at->length()->integer_constant_value(true, val, &type))
+	{
+	  if (this->vals_->size() > mpz_get_ui(val))
+	    this->report_error(_("too many elements in composite literal"));
+	}
+      mpz_clear(val);
+    }
+}
+
+// Get a constructor tree for the array values.
+
+tree
+Array_construction_expression::get_constructor_tree(Translate_context* context,
+						    tree type_tree)
+{
+  VEC(constructor_elt,gc)* values = VEC_alloc(constructor_elt, gc,
+					      (this->vals_ == NULL
+					       ? 0
+					       : this->vals_->size()));
+  Type* element_type = this->type_->array_type()->element_type();
+  bool is_constant = true;
+  if (this->vals_ != NULL)
+    {
+      size_t i = 0;
+      for (Expression_list::const_iterator pv = this->vals_->begin();
+	   pv != this->vals_->end();
+	   ++pv, ++i)
+	{
+	  constructor_elt* elt = VEC_quick_push(constructor_elt, values, NULL);
+	  elt->index = size_int(i);
+	  if (*pv == NULL)
+	    elt->value = element_type->get_init_tree(context->gogo(), false);
+	  else
+	    {
+	      tree value_tree = (*pv)->get_tree(context);
+	      elt->value = Expression::convert_for_assignment(context,
+							      element_type,
+							      (*pv)->type(),
+							      value_tree,
+							      this->location());
+	    }
+	  if (elt->value == error_mark_node)
+	    return error_mark_node;
+	  if (!TREE_CONSTANT(elt->value))
+	    is_constant = false;
+	}
+    }
+
+  tree ret = build_constructor(type_tree, values);
+  if (is_constant)
+    TREE_CONSTANT(ret) = 1;
+  return ret;
+}
+
+// Export an array construction.
+
+void
+Array_construction_expression::do_export(Export* exp) const
+{
+  exp->write_c_string("convert(");
+  exp->write_type(this->type_);
+  if (this->vals_ != NULL)
+    {
+      for (Expression_list::const_iterator pv = this->vals_->begin();
+	   pv != this->vals_->end();
+	   ++pv)
+	{
+	  exp->write_c_string(", ");
+	  if (*pv != NULL)
+	    (*pv)->export_expression(exp);
+	}
+    }
+  exp->write_c_string(")");
+}
+
+// Construct a fixed array.
+
+class Fixed_array_construction_expression :
+  public Array_construction_expression
+{
+ public:
+  Fixed_array_construction_expression(Type* type, Expression_list* vals,
+				      source_location location)
+    : Array_construction_expression(EXPRESSION_FIXED_ARRAY_CONSTRUCTION,
+				    type, vals, location)
+  {
+    gcc_assert(type->array_type() != NULL
+	       && type->array_type()->length() != NULL);
+  }
+
+ protected:
+  Expression*
+  do_copy()
+  {
+    return new Fixed_array_construction_expression(this->type(),
+						   (this->vals() == NULL
+						    ? NULL
+						    : this->vals()->copy()),
+						   this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context*);
+};
+
+// Return a tree for constructing a fixed array.
+
+tree
+Fixed_array_construction_expression::do_get_tree(Translate_context* context)
+{
+  return this->get_constructor_tree(context,
+				    this->type()->get_tree(context->gogo()));
+}
+
+// Construct an open array.
+
+class Open_array_construction_expression : public Array_construction_expression
+{
+ public:
+  Open_array_construction_expression(Type* type, Expression_list* vals,
+				     source_location location)
+    : Array_construction_expression(EXPRESSION_OPEN_ARRAY_CONSTRUCTION,
+				    type, vals, location)
+  {
+    gcc_assert(type->array_type() != NULL
+	       && type->array_type()->length() == NULL);
+  }
+
+ protected:
+  // Note that taking the address of an open array literal is invalid.
+
+  Expression*
+  do_copy()
+  {
+    return new Open_array_construction_expression(this->type(),
+						  (this->vals() == NULL
+						   ? NULL
+						   : this->vals()->copy()),
+						  this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context*);
+};
+
+// Return a tree for constructing an open array.
+
+tree
+Open_array_construction_expression::do_get_tree(Translate_context* context)
+{
+  Array_type* array_type = this->type()->array_type();
+  if (array_type == NULL)
+    {
+      gcc_assert(this->type()->is_error_type());
+      return error_mark_node;
+    }
+
+  Type* element_type = array_type->element_type();
+  tree element_type_tree = element_type->get_tree(context->gogo());
+  if (element_type_tree == error_mark_node)
+    return error_mark_node;
+
+  tree values;
+  tree length_tree;
+  if (this->vals() == NULL || this->vals()->empty())
+    {
+      // We need to create a unique value.
+      tree max = size_int(0);
+      tree constructor_type = build_array_type(element_type_tree,
+					       build_index_type(max));
+      if (constructor_type == error_mark_node)
+	return error_mark_node;
+      VEC(constructor_elt,gc)* vec = VEC_alloc(constructor_elt, gc, 1);
+      constructor_elt* elt = VEC_quick_push(constructor_elt, vec, NULL);
+      elt->index = size_int(0);
+      elt->value = element_type->get_init_tree(context->gogo(), false);
+      values = build_constructor(constructor_type, vec);
+      if (TREE_CONSTANT(elt->value))
+	TREE_CONSTANT(values) = 1;
+      length_tree = size_int(0);
+    }
+  else
+    {
+      tree max = size_int(this->vals()->size() - 1);
+      tree constructor_type = build_array_type(element_type_tree,
+					       build_index_type(max));
+      if (constructor_type == error_mark_node)
+	return error_mark_node;
+      values = this->get_constructor_tree(context, constructor_type);
+      length_tree = size_int(this->vals()->size());
+    }
+
+  if (values == error_mark_node)
+    return error_mark_node;
+
+  bool is_constant_initializer = TREE_CONSTANT(values);
+
+  // We have to copy the initial values into heap memory if we are in
+  // a function or if the values are not constants.  We also have to
+  // copy them if they may contain pointers in a non-constant context,
+  // as otherwise the garbage collector won't see them.
+  bool copy_to_heap = (context->function() != NULL
+		       || !is_constant_initializer
+		       || (element_type->has_pointer()
+			   && !context->is_const()));
+
+  if (is_constant_initializer)
+    {
+      tree tmp = build_decl(this->location(), VAR_DECL,
+			    create_tmp_var_name("C"), TREE_TYPE(values));
+      DECL_EXTERNAL(tmp) = 0;
+      TREE_PUBLIC(tmp) = 0;
+      TREE_STATIC(tmp) = 1;
+      DECL_ARTIFICIAL(tmp) = 1;
+      if (copy_to_heap)
+	{
+	  // If we are not copying the value to the heap, we will only
+	  // initialize the value once, so we can use this directly
+	  // rather than copying it.  In that case we can't make it
+	  // read-only, because the program is permitted to change it.
+	  TREE_READONLY(tmp) = 1;
+	  TREE_CONSTANT(tmp) = 1;
+	}
+      DECL_INITIAL(tmp) = values;
+      rest_of_decl_compilation(tmp, 1, 0);
+      values = tmp;
+    }
+
+  tree space;
+  tree set;
+  if (!copy_to_heap)
+    {
+      // the initializer will only run once.
+      space = build_fold_addr_expr(values);
+      set = NULL_TREE;
+    }
+  else
+    {
+      tree memsize = TYPE_SIZE_UNIT(TREE_TYPE(values));
+      space = context->gogo()->allocate_memory(element_type, memsize,
+					       this->location());
+      space = save_expr(space);
+
+      tree s = fold_convert(build_pointer_type(TREE_TYPE(values)), space);
+      tree ref = build_fold_indirect_ref_loc(this->location(), s);
+      TREE_THIS_NOTRAP(ref) = 1;
+      set = build2(MODIFY_EXPR, void_type_node, ref, values);
+    }
+
+  // Build a constructor for the open array.
+
+  tree type_tree = this->type()->get_tree(context->gogo());
+  if (type_tree == error_mark_node)
+    return error_mark_node;
+  gcc_assert(TREE_CODE(type_tree) == RECORD_TYPE);
+
+  VEC(constructor_elt,gc)* init = VEC_alloc(constructor_elt, gc, 3);
+
+  constructor_elt* elt = VEC_quick_push(constructor_elt, init, NULL);
+  tree field = TYPE_FIELDS(type_tree);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__values") == 0);
+  elt->index = field;
+  elt->value = fold_convert(TREE_TYPE(field), space);
+
+  elt = VEC_quick_push(constructor_elt, init, NULL);
+  field = DECL_CHAIN(field);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__count") == 0);
+  elt->index = field;
+  elt->value = fold_convert(TREE_TYPE(field), length_tree);
+
+  elt = VEC_quick_push(constructor_elt, init, NULL);
+  field = DECL_CHAIN(field);
+  gcc_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)),"__capacity") == 0);
+  elt->index = field;
+  elt->value = fold_convert(TREE_TYPE(field), length_tree);
+
+  tree constructor = build_constructor(type_tree, init);
+  if (constructor == error_mark_node)
+    return error_mark_node;
+  if (!copy_to_heap)
+    TREE_CONSTANT(constructor) = 1;
+
+  if (set == NULL_TREE)
+    return constructor;
+  else
+    return build2(COMPOUND_EXPR, type_tree, set, constructor);
+}
+
+// Make a slice composite literal.  This is used by the type
+// descriptor code.
+
+Expression*
+Expression::make_slice_composite_literal(Type* type, Expression_list* vals,
+					 source_location location)
+{
+  gcc_assert(type->is_open_array_type());
+  return new Open_array_construction_expression(type, vals, location);
+}
+
+// Construct a map.
+
+class Map_construction_expression : public Expression
+{
+ public:
+  Map_construction_expression(Type* type, Expression_list* vals,
+			      source_location location)
+    : Expression(EXPRESSION_MAP_CONSTRUCTION, location),
+      type_(type), vals_(vals)
+  { gcc_assert(vals == NULL || vals->size() % 2 == 0); }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse);
+
+  Type*
+  do_type()
+  { return this->type_; }
+
+  void
+  do_determine_type(const Type_context*);
+
+  void
+  do_check_types(Gogo*);
+
+  Expression*
+  do_copy()
+  {
+    return new Map_construction_expression(this->type_, this->vals_->copy(),
+					   this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context*);
+
+  void
+  do_export(Export*) const;
+
+ private:
+  // The type of the map to construct.
+  Type* type_;
+  // The list of values.
+  Expression_list* vals_;
+};
+
+// Traversal.
+
+int
+Map_construction_expression::do_traverse(Traverse* traverse)
+{
+  if (this->vals_ != NULL
+      && this->vals_->traverse(traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  if (Type::traverse(this->type_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return TRAVERSE_CONTINUE;
+}
+
+// Final type determination.
+
+void
+Map_construction_expression::do_determine_type(const Type_context*)
+{
+  if (this->vals_ == NULL)
+    return;
+
+  Map_type* mt = this->type_->map_type();
+  Type_context key_context(mt->key_type(), false);
+  Type_context val_context(mt->val_type(), false);
+  for (Expression_list::const_iterator pv = this->vals_->begin();
+       pv != this->vals_->end();
+       ++pv)
+    {
+      (*pv)->determine_type(&key_context);
+      ++pv;
+      (*pv)->determine_type(&val_context);
+    }
+}
+
+// Check types.
+
+void
+Map_construction_expression::do_check_types(Gogo*)
+{
+  if (this->vals_ == NULL)
+    return;
+
+  Map_type* mt = this->type_->map_type();
+  int i = 0;
+  Type* key_type = mt->key_type();
+  Type* val_type = mt->val_type();
+  for (Expression_list::const_iterator pv = this->vals_->begin();
+       pv != this->vals_->end();
+       ++pv, ++i)
+    {
+      if (!Type::are_assignable(key_type, (*pv)->type(), NULL))
+	{
+	  error_at((*pv)->location(),
+		   "incompatible type for element %d key in map construction",
+		   i + 1);
+	  this->set_is_error();
+	}
+      ++pv;
+      if (!Type::are_assignable(val_type, (*pv)->type(), NULL))
+	{
+	  error_at((*pv)->location(),
+		   ("incompatible type for element %d value "
+		    "in map construction"),
+		   i + 1);
+	  this->set_is_error();
+	}
+    }
+}
+
+// Return a tree for constructing a map.
+
+tree
+Map_construction_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  source_location loc = this->location();
+
+  Map_type* mt = this->type_->map_type();
+
+  // Build a struct to hold the key and value.
+  tree struct_type = make_node(RECORD_TYPE);
+
+  Type* key_type = mt->key_type();
+  tree id = get_identifier("__key");
+  tree key_type_tree = key_type->get_tree(gogo);
+  if (key_type_tree == error_mark_node)
+    return error_mark_node;
+  tree key_field = build_decl(loc, FIELD_DECL, id, key_type_tree);
+  DECL_CONTEXT(key_field) = struct_type;
+  TYPE_FIELDS(struct_type) = key_field;
+
+  Type* val_type = mt->val_type();
+  id = get_identifier("__val");
+  tree val_type_tree = val_type->get_tree(gogo);
+  if (val_type_tree == error_mark_node)
+    return error_mark_node;
+  tree val_field = build_decl(loc, FIELD_DECL, id, val_type_tree);
+  DECL_CONTEXT(val_field) = struct_type;
+  DECL_CHAIN(key_field) = val_field;
+
+  layout_type(struct_type);
+
+  bool is_constant = true;
+  size_t i = 0;
+  tree valaddr;
+  tree make_tmp;
+
+  if (this->vals_ == NULL || this->vals_->empty())
+    {
+      valaddr = null_pointer_node;
+      make_tmp = NULL_TREE;
+    }
+  else
+    {
+      VEC(constructor_elt,gc)* values = VEC_alloc(constructor_elt, gc,
+						  this->vals_->size() / 2);
+
+      for (Expression_list::const_iterator pv = this->vals_->begin();
+	   pv != this->vals_->end();
+	   ++pv, ++i)
+	{
+	  bool one_is_constant = true;
+
+	  VEC(constructor_elt,gc)* one = VEC_alloc(constructor_elt, gc, 2);
+
+	  constructor_elt* elt = VEC_quick_push(constructor_elt, one, NULL);
+	  elt->index = key_field;
+	  tree val_tree = (*pv)->get_tree(context);
+	  elt->value = Expression::convert_for_assignment(context, key_type,
+							  (*pv)->type(),
+							  val_tree, loc);
+	  if (elt->value == error_mark_node)
+	    return error_mark_node;
+	  if (!TREE_CONSTANT(elt->value))
+	    one_is_constant = false;
+
+	  ++pv;
+
+	  elt = VEC_quick_push(constructor_elt, one, NULL);
+	  elt->index = val_field;
+	  val_tree = (*pv)->get_tree(context);
+	  elt->value = Expression::convert_for_assignment(context, val_type,
+							  (*pv)->type(),
+							  val_tree, loc);
+	  if (elt->value == error_mark_node)
+	    return error_mark_node;
+	  if (!TREE_CONSTANT(elt->value))
+	    one_is_constant = false;
+
+	  elt = VEC_quick_push(constructor_elt, values, NULL);
+	  elt->index = size_int(i);
+	  elt->value = build_constructor(struct_type, one);
+	  if (one_is_constant)
+	    TREE_CONSTANT(elt->value) = 1;
+	  else
+	    is_constant = false;
+	}
+
+      tree index_type = build_index_type(size_int(i - 1));
+      tree array_type = build_array_type(struct_type, index_type);
+      tree init = build_constructor(array_type, values);
+      if (is_constant)
+	TREE_CONSTANT(init) = 1;
+      tree tmp;
+      if (current_function_decl != NULL)
+	{
+	  tmp = create_tmp_var(array_type, get_name(array_type));
+	  DECL_INITIAL(tmp) = init;
+	  make_tmp = fold_build1_loc(loc, DECL_EXPR, void_type_node, tmp);
+	  TREE_ADDRESSABLE(tmp) = 1;
+	}
+      else
+	{
+	  tmp = build_decl(loc, VAR_DECL, create_tmp_var_name("M"), array_type);
+	  DECL_EXTERNAL(tmp) = 0;
+	  TREE_PUBLIC(tmp) = 0;
+	  TREE_STATIC(tmp) = 1;
+	  DECL_ARTIFICIAL(tmp) = 1;
+	  if (!TREE_CONSTANT(init))
+	    make_tmp = fold_build2_loc(loc, INIT_EXPR, void_type_node, tmp,
+				       init);
+	  else
+	    {
+	      TREE_READONLY(tmp) = 1;
+	      TREE_CONSTANT(tmp) = 1;
+	      DECL_INITIAL(tmp) = init;
+	      make_tmp = NULL_TREE;
+	    }
+	  rest_of_decl_compilation(tmp, 1, 0);
+	}
+
+      valaddr = build_fold_addr_expr(tmp);
+    }
+
+  tree descriptor = gogo->map_descriptor(mt);
+
+  tree type_tree = this->type_->get_tree(gogo);
+  if (type_tree == error_mark_node)
+    return error_mark_node;
+
+  static tree construct_map_fndecl;
+  tree call = Gogo::call_builtin(&construct_map_fndecl,
+				 loc,
+				 "__go_construct_map",
+				 6,
+				 type_tree,
+				 TREE_TYPE(descriptor),
+				 descriptor,
+				 sizetype,
+				 size_int(i),
+				 sizetype,
+				 TYPE_SIZE_UNIT(struct_type),
+				 sizetype,
+				 byte_position(val_field),
+				 sizetype,
+				 TYPE_SIZE_UNIT(TREE_TYPE(val_field)),
+				 const_ptr_type_node,
+				 fold_convert(const_ptr_type_node, valaddr));
+  if (call == error_mark_node)
+    return error_mark_node;
+
+  tree ret;
+  if (make_tmp == NULL)
+    ret = call;
+  else
+    ret = fold_build2_loc(loc, COMPOUND_EXPR, type_tree, make_tmp, call);
+  return ret;
+}
+
+// Export an array construction.
+
+void
+Map_construction_expression::do_export(Export* exp) const
+{
+  exp->write_c_string("convert(");
+  exp->write_type(this->type_);
+  for (Expression_list::const_iterator pv = this->vals_->begin();
+       pv != this->vals_->end();
+       ++pv)
+    {
+      exp->write_c_string(", ");
+      (*pv)->export_expression(exp);
+    }
+  exp->write_c_string(")");
+}
+
+// A general composite literal.  This is lowered to a type specific
+// version.
+
+class Composite_literal_expression : public Parser_expression
+{
+ public:
+  Composite_literal_expression(Type* type, int depth, bool has_keys,
+			       Expression_list* vals, source_location location)
+    : Parser_expression(EXPRESSION_COMPOSITE_LITERAL, location),
+      type_(type), depth_(depth), vals_(vals), has_keys_(has_keys)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse);
+
+  Expression*
+  do_lower(Gogo*, Named_object*, int);
+
+  Expression*
+  do_copy()
+  {
+    return new Composite_literal_expression(this->type_, this->depth_,
+					    this->has_keys_,
+					    (this->vals_ == NULL
+					     ? NULL
+					     : this->vals_->copy()),
+					    this->location());
+  }
+
+ private:
+  Expression*
+  lower_struct(Gogo*, Type*);
+
+  Expression*
+  lower_array(Type*);
+
+  Expression*
+  make_array(Type*, Expression_list*);
+
+  Expression*
+  lower_map(Gogo*, Named_object*, Type*);
+
+  // The type of the composite literal.
+  Type* type_;
+  // The depth within a list of composite literals within a composite
+  // literal, when the type is omitted.
+  int depth_;
+  // The values to put in the composite literal.
+  Expression_list* vals_;
+  // If this is true, then VALS_ is a list of pairs: a key and a
+  // value.  In an array initializer, a missing key will be NULL.
+  bool has_keys_;
+};
+
+// Traversal.
+
+int
+Composite_literal_expression::do_traverse(Traverse* traverse)
+{
+  if (this->vals_ != NULL
+      && this->vals_->traverse(traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return Type::traverse(this->type_, traverse);
+}
+
+// Lower a generic composite literal into a specific version based on
+// the type.
+
+Expression*
+Composite_literal_expression::do_lower(Gogo* gogo, Named_object* function, int)
+{
+  Type* type = this->type_;
+
+  for (int depth = this->depth_; depth > 0; --depth)
+    {
+      if (type->array_type() != NULL)
+	type = type->array_type()->element_type();
+      else if (type->map_type() != NULL)
+	type = type->map_type()->val_type();
+      else
+	{
+	  if (!type->is_error_type())
+	    error_at(this->location(),
+		     ("may only omit types within composite literals "
+		      "of slice, array, or map type"));
+	  return Expression::make_error(this->location());
+	}
+    }
+
+  if (type->is_error_type())
+    return Expression::make_error(this->location());
+  else if (type->struct_type() != NULL)
+    return this->lower_struct(gogo, type);
+  else if (type->array_type() != NULL)
+    return this->lower_array(type);
+  else if (type->map_type() != NULL)
+    return this->lower_map(gogo, function, type);
+  else
+    {
+      error_at(this->location(),
+	       ("expected struct, slice, array, or map type "
+		"for composite literal"));
+      return Expression::make_error(this->location());
+    }
+}
+
+// Lower a struct composite literal.
+
+Expression*
+Composite_literal_expression::lower_struct(Gogo* gogo, Type* type)
+{
+  source_location location = this->location();
+  Struct_type* st = type->struct_type();
+  if (this->vals_ == NULL || !this->has_keys_)
+    return new Struct_construction_expression(type, this->vals_, location);
+
+  size_t field_count = st->field_count();
+  std::vector<Expression*> vals(field_count);
+  Expression_list::const_iterator p = this->vals_->begin();
+  while (p != this->vals_->end())
+    {
+      Expression* name_expr = *p;
+
+      ++p;
+      gcc_assert(p != this->vals_->end());
+      Expression* val = *p;
+
+      ++p;
+
+      if (name_expr == NULL)
+	{
+	  error_at(val->location(), "mixture of field and value initializers");
+	  return Expression::make_error(location);
+	}
+
+      bool bad_key = false;
+      std::string name;
+      const Named_object* no = NULL;
+      switch (name_expr->classification())
+	{
+	case EXPRESSION_UNKNOWN_REFERENCE:
+	  name = name_expr->unknown_expression()->name();
+	  break;
+
+	case EXPRESSION_CONST_REFERENCE:
+	  no = static_cast<Const_expression*>(name_expr)->named_object();
+	  break;
+
+	case EXPRESSION_TYPE:
+	  {
+	    Type* t = name_expr->type();
+	    Named_type* nt = t->named_type();
+	    if (nt == NULL)
+	      bad_key = true;
+	    else
+	      no = nt->named_object();
+	  }
+	  break;
+
+	case EXPRESSION_VAR_REFERENCE:
+	  no = name_expr->var_expression()->named_object();
+	  break;
+
+	case EXPRESSION_FUNC_REFERENCE:
+	  no = name_expr->func_expression()->named_object();
+	  break;
+
+	case EXPRESSION_UNARY:
+	  // If there is a local variable around with the same name as
+	  // the field, and this occurs in the closure, then the
+	  // parser may turn the field reference into an indirection
+	  // through the closure.  FIXME: This is a mess.
+	  {
+	    bad_key = true;
+	    Unary_expression* ue = static_cast<Unary_expression*>(name_expr);
+	    if (ue->op() == OPERATOR_MULT)
+	      {
+		Field_reference_expression* fre =
+		  ue->operand()->field_reference_expression();
+		if (fre != NULL)
+		  {
+		    Struct_type* st =
+		      fre->expr()->type()->deref()->struct_type();
+		    if (st != NULL)
+		      {
+			const Struct_field* sf = st->field(fre->field_index());
+			name = sf->field_name();
+			char buf[20];
+			snprintf(buf, sizeof buf, "%u", fre->field_index());
+			size_t buflen = strlen(buf);
+			if (name.compare(name.length() - buflen, buflen, buf)
+			    == 0)
+			  {
+			    name = name.substr(0, name.length() - buflen);
+			    bad_key = false;
+			  }
+		      }
+		  }
+	      }
+	  }
+	  break;
+
+	default:
+	  bad_key = true;
+	  break;
+	}
+      if (bad_key)
+	{
+	  error_at(name_expr->location(), "expected struct field name");
+	  return Expression::make_error(location);
+	}
+
+      if (no != NULL)
+	{
+	  name = no->name();
+
+	  // A predefined name won't be packed.  If it starts with a
+	  // lower case letter we need to check for that case, because
+	  // the field name will be packed.
+	  if (!Gogo::is_hidden_name(name)
+	      && name[0] >= 'a'
+	      && name[0] <= 'z')
+	    {
+	      Named_object* gno = gogo->lookup_global(name.c_str());
+	      if (gno == no)
+		name = gogo->pack_hidden_name(name, false);
+	    }
+	}
+
+      unsigned int index;
+      const Struct_field* sf = st->find_local_field(name, &index);
+      if (sf == NULL)
+	{
+	  error_at(name_expr->location(), "unknown field %qs in %qs",
+		   Gogo::message_name(name).c_str(),
+		   (type->named_type() != NULL
+		    ? type->named_type()->message_name().c_str()
+		    : "unnamed struct"));
+	  return Expression::make_error(location);
+	}
+      if (vals[index] != NULL)
+	{
+	  error_at(name_expr->location(),
+		   "duplicate value for field %qs in %qs",
+		   Gogo::message_name(name).c_str(),
+		   (type->named_type() != NULL
+		    ? type->named_type()->message_name().c_str()
+		    : "unnamed struct"));
+	  return Expression::make_error(location);
+	}
+
+      vals[index] = val;
+    }
+
+  Expression_list* list = new Expression_list;
+  list->reserve(field_count);
+  for (size_t i = 0; i < field_count; ++i)
+    list->push_back(vals[i]);
+
+  return new Struct_construction_expression(type, list, location);
+}
+
+// Lower an array composite literal.
+
+Expression*
+Composite_literal_expression::lower_array(Type* type)
+{
+  source_location location = this->location();
+  if (this->vals_ == NULL || !this->has_keys_)
+    return this->make_array(type, this->vals_);
+
+  std::vector<Expression*> vals;
+  vals.reserve(this->vals_->size());
+  unsigned long index = 0;
+  Expression_list::const_iterator p = this->vals_->begin();
+  while (p != this->vals_->end())
+    {
+      Expression* index_expr = *p;
+
+      ++p;
+      gcc_assert(p != this->vals_->end());
+      Expression* val = *p;
+
+      ++p;
+
+      if (index_expr != NULL)
+	{
+	  mpz_t ival;
+	  mpz_init(ival);
+
+	  Type* dummy;
+	  if (!index_expr->integer_constant_value(true, ival, &dummy))
+	    {
+	      mpz_clear(ival);
+	      error_at(index_expr->location(),
+		       "index expression is not integer constant");
+	      return Expression::make_error(location);
+	    }
+
+	  if (mpz_sgn(ival) < 0)
+	    {
+	      mpz_clear(ival);
+	      error_at(index_expr->location(), "index expression is negative");
+	      return Expression::make_error(location);
+	    }
+
+	  index = mpz_get_ui(ival);
+	  if (mpz_cmp_ui(ival, index) != 0)
+	    {
+	      mpz_clear(ival);
+	      error_at(index_expr->location(), "index value overflow");
+	      return Expression::make_error(location);
+	    }
+
+	  Named_type* ntype = Type::lookup_integer_type("int");
+	  Integer_type* inttype = ntype->integer_type();
+	  mpz_t max;
+	  mpz_init_set_ui(max, 1);
+	  mpz_mul_2exp(max, max, inttype->bits() - 1);
+	  bool ok = mpz_cmp(ival, max) < 0;
+	  mpz_clear(max);
+	  if (!ok)
+	    {
+	      mpz_clear(ival);
+	      error_at(index_expr->location(), "index value overflow");
+	      return Expression::make_error(location);
+	    }
+
+	  mpz_clear(ival);
+
+	  // FIXME: Our representation isn't very good; this avoids
+	  // thrashing.
+	  if (index > 0x1000000)
+	    {
+	      error_at(index_expr->location(), "index too large for compiler");
+	      return Expression::make_error(location);
+	    }
+	}
+
+      if (index == vals.size())
+	vals.push_back(val);
+      else
+	{
+	  if (index > vals.size())
+	    {
+	      vals.reserve(index + 32);
+	      vals.resize(index + 1, static_cast<Expression*>(NULL));
+	    }
+	  if (vals[index] != NULL)
+	    {
+	      error_at((index_expr != NULL
+			? index_expr->location()
+			: val->location()),
+		       "duplicate value for index %lu",
+		       index);
+	      return Expression::make_error(location);
+	    }
+	  vals[index] = val;
+	}
+
+      ++index;
+    }
+
+  size_t size = vals.size();
+  Expression_list* list = new Expression_list;
+  list->reserve(size);
+  for (size_t i = 0; i < size; ++i)
+    list->push_back(vals[i]);
+
+  return this->make_array(type, list);
+}
+
+// Actually build the array composite literal. This handles
+// [...]{...}.
+
+Expression*
+Composite_literal_expression::make_array(Type* type, Expression_list* vals)
+{
+  source_location location = this->location();
+  Array_type* at = type->array_type();
+  if (at->length() != NULL && at->length()->is_nil_expression())
+    {
+      size_t size = vals == NULL ? 0 : vals->size();
+      mpz_t vlen;
+      mpz_init_set_ui(vlen, size);
+      Expression* elen = Expression::make_integer(&vlen, NULL, location);
+      mpz_clear(vlen);
+      at = Type::make_array_type(at->element_type(), elen);
+      type = at;
+    }
+  if (at->length() != NULL)
+    return new Fixed_array_construction_expression(type, vals, location);
+  else
+    return new Open_array_construction_expression(type, vals, location);
+}
+
+// Lower a map composite literal.
+
+Expression*
+Composite_literal_expression::lower_map(Gogo* gogo, Named_object* function,
+					Type* type)
+{
+  source_location location = this->location();
+  if (this->vals_ != NULL)
+    {
+      if (!this->has_keys_)
+	{
+	  error_at(location, "map composite literal must have keys");
+	  return Expression::make_error(location);
+	}
+
+      for (Expression_list::iterator p = this->vals_->begin();
+	   p != this->vals_->end();
+	   p += 2)
+	{
+	  if (*p == NULL)
+	    {
+	      ++p;
+	      error_at((*p)->location(),
+		       "map composite literal must have keys for every value");
+	      return Expression::make_error(location);
+	    }
+	  // Make sure we have lowered the key; it may not have been
+	  // lowered in order to handle keys for struct composite
+	  // literals.  Lower it now to get the right error message.
+	  if ((*p)->unknown_expression() != NULL)
+	    {
+	      (*p)->unknown_expression()->clear_is_composite_literal_key();
+	      gogo->lower_expression(function, &*p);
+	      gcc_assert((*p)->is_error_expression());
+	      return Expression::make_error(location);
+	    }
+	}
+    }
+
+  return new Map_construction_expression(type, this->vals_, location);
+}
+
+// Make a composite literal expression.
+
+Expression*
+Expression::make_composite_literal(Type* type, int depth, bool has_keys,
+				   Expression_list* vals,
+				   source_location location)
+{
+  return new Composite_literal_expression(type, depth, has_keys, vals,
+					  location);
+}
+
+// Return whether this expression is a composite literal.
+
+bool
+Expression::is_composite_literal() const
+{
+  switch (this->classification_)
+    {
+    case EXPRESSION_COMPOSITE_LITERAL:
+    case EXPRESSION_STRUCT_CONSTRUCTION:
+    case EXPRESSION_FIXED_ARRAY_CONSTRUCTION:
+    case EXPRESSION_OPEN_ARRAY_CONSTRUCTION:
+    case EXPRESSION_MAP_CONSTRUCTION:
+      return true;
+    default:
+      return false;
+    }
+}
+
+// Return whether this expression is a composite literal which is not
+// constant.
+
+bool
+Expression::is_nonconstant_composite_literal() const
+{
+  switch (this->classification_)
+    {
+    case EXPRESSION_STRUCT_CONSTRUCTION:
+      {
+	const Struct_construction_expression *psce =
+	  static_cast<const Struct_construction_expression*>(this);
+	return !psce->is_constant_struct();
+      }
+    case EXPRESSION_FIXED_ARRAY_CONSTRUCTION:
+      {
+	const Fixed_array_construction_expression *pace =
+	  static_cast<const Fixed_array_construction_expression*>(this);
+	return !pace->is_constant_array();
+      }
+    case EXPRESSION_OPEN_ARRAY_CONSTRUCTION:
+      {
+	const Open_array_construction_expression *pace =
+	  static_cast<const Open_array_construction_expression*>(this);
+	return !pace->is_constant_array();
+      }
+    case EXPRESSION_MAP_CONSTRUCTION:
+      return true;
+    default:
+      return false;
+    }
+}
+
+// Return true if this is a reference to a local variable.
+
+bool
+Expression::is_local_variable() const
+{
+  const Var_expression* ve = this->var_expression();
+  if (ve == NULL)
+    return false;
+  const Named_object* no = ve->named_object();
+  return (no->is_result_variable()
+	  || (no->is_variable() && !no->var_value()->is_global()));
+}
+
+// Class Type_guard_expression.
+
+// Traversal.
+
+int
+Type_guard_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->expr_, traverse) == TRAVERSE_EXIT
+      || Type::traverse(this->type_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return TRAVERSE_CONTINUE;
+}
+
+// Check types of a type guard expression.  The expression must have
+// an interface type, but the actual type conversion is checked at run
+// time.
+
+void
+Type_guard_expression::do_check_types(Gogo*)
+{
+  // 6g permits using a type guard with unsafe.pointer; we are
+  // compatible.
+  Type* expr_type = this->expr_->type();
+  if (expr_type->is_unsafe_pointer_type())
+    {
+      if (this->type_->points_to() == NULL
+	  && (this->type_->integer_type() == NULL
+	      || (this->type_->forwarded()
+		  != Type::lookup_integer_type("uintptr"))))
+	this->report_error(_("invalid unsafe.Pointer conversion"));
+    }
+  else if (this->type_->is_unsafe_pointer_type())
+    {
+      if (expr_type->points_to() == NULL
+	  && (expr_type->integer_type() == NULL
+	      || (expr_type->forwarded()
+		  != Type::lookup_integer_type("uintptr"))))
+	this->report_error(_("invalid unsafe.Pointer conversion"));
+    }
+  else if (expr_type->interface_type() == NULL)
+    {
+      if (!expr_type->is_error_type() && !this->type_->is_error_type())
+	this->report_error(_("type assertion only valid for interface types"));
+      this->set_is_error();
+    }
+  else if (this->type_->interface_type() == NULL)
+    {
+      std::string reason;
+      if (!expr_type->interface_type()->implements_interface(this->type_,
+							     &reason))
+	{
+	  if (!this->type_->is_error_type())
+	    {
+	      if (reason.empty())
+		this->report_error(_("impossible type assertion: "
+				     "type does not implement interface"));
+	      else
+		error_at(this->location(),
+			 ("impossible type assertion: "
+			  "type does not implement interface (%s)"),
+			 reason.c_str());
+	    }
+	  this->set_is_error();
+	}
+    }
+}
+
+// Return a tree for a type guard expression.
+
+tree
+Type_guard_expression::do_get_tree(Translate_context* context)
+{
+  Gogo* gogo = context->gogo();
+  tree expr_tree = this->expr_->get_tree(context);
+  if (expr_tree == error_mark_node)
+    return error_mark_node;
+  Type* expr_type = this->expr_->type();
+  if ((this->type_->is_unsafe_pointer_type()
+       && (expr_type->points_to() != NULL
+	   || expr_type->integer_type() != NULL))
+      || (expr_type->is_unsafe_pointer_type()
+	  && this->type_->points_to() != NULL))
+    return convert_to_pointer(this->type_->get_tree(gogo), expr_tree);
+  else if (expr_type->is_unsafe_pointer_type()
+	   && this->type_->integer_type() != NULL)
+    return convert_to_integer(this->type_->get_tree(gogo), expr_tree);
+  else if (this->type_->interface_type() != NULL)
+    return Expression::convert_interface_to_interface(context, this->type_,
+						      this->expr_->type(),
+						      expr_tree, true,
+						      this->location());
+  else
+    return Expression::convert_for_assignment(context, this->type_,
+					      this->expr_->type(), expr_tree,
+					      this->location());
+}
+
+// Make a type guard expression.
+
+Expression*
+Expression::make_type_guard(Expression* expr, Type* type,
+			    source_location location)
+{
+  return new Type_guard_expression(expr, type, location);
+}
+
+// Class Heap_composite_expression.
+
+// When you take the address of a composite literal, it is allocated
+// on the heap.  This class implements that.
+
+class Heap_composite_expression : public Expression
+{
+ public:
+  Heap_composite_expression(Expression* expr, source_location location)
+    : Expression(EXPRESSION_HEAP_COMPOSITE, location),
+      expr_(expr)
+  { }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse)
+  { return Expression::traverse(&this->expr_, traverse); }
+
+  Type*
+  do_type()
+  { return Type::make_pointer_type(this->expr_->type()); }
+
+  void
+  do_determine_type(const Type_context*)
+  { this->expr_->determine_type_no_context(); }
+
+  Expression*
+  do_copy()
+  {
+    return Expression::make_heap_composite(this->expr_->copy(),
+					   this->location());
+  }
+
+  tree
+  do_get_tree(Translate_context*);
+
+  // We only export global objects, and the parser does not generate
+  // this in global scope.
+  void
+  do_export(Export*) const
+  { gcc_unreachable(); }
+
+ private:
+  // The composite literal which is being put on the heap.
+  Expression* expr_;
+};
+
+// Return a tree which allocates a composite literal on the heap.
+
+tree
+Heap_composite_expression::do_get_tree(Translate_context* context)
+{
+  tree expr_tree = this->expr_->get_tree(context);
+  if (expr_tree == error_mark_node)
+    return error_mark_node;
+  tree expr_size = TYPE_SIZE_UNIT(TREE_TYPE(expr_tree));
+  gcc_assert(TREE_CODE(expr_size) == INTEGER_CST);
+  tree space = context->gogo()->allocate_memory(this->expr_->type(),
+						expr_size, this->location());
+  space = fold_convert(build_pointer_type(TREE_TYPE(expr_tree)), space);
+  space = save_expr(space);
+  tree ref = build_fold_indirect_ref_loc(this->location(), space);
+  TREE_THIS_NOTRAP(ref) = 1;
+  tree ret = build2(COMPOUND_EXPR, TREE_TYPE(space),
+		    build2(MODIFY_EXPR, void_type_node, ref, expr_tree),
+		    space);
+  SET_EXPR_LOCATION(ret, this->location());
+  return ret;
+}
+
+// Allocate a composite literal on the heap.
+
+Expression*
+Expression::make_heap_composite(Expression* expr, source_location location)
+{
+  return new Heap_composite_expression(expr, location);
+}
+
+// Class Receive_expression.
+
+// Return the type of a receive expression.
+
+Type*
+Receive_expression::do_type()
+{
+  Channel_type* channel_type = this->channel_->type()->channel_type();
+  if (channel_type == NULL)
+    return Type::make_error_type();
+  return channel_type->element_type();
+}
+
+// Check types for a receive expression.
+
+void
+Receive_expression::do_check_types(Gogo*)
+{
+  Type* type = this->channel_->type();
+  if (type->is_error_type())
+    {
+      this->set_is_error();
+      return;
+    }
+  if (type->channel_type() == NULL)
+    {
+      this->report_error(_("expected channel"));
+      return;
+    }
+  if (!type->channel_type()->may_receive())
+    {
+      this->report_error(_("invalid receive on send-only channel"));
+      return;
+    }
+}
+
+// Get a tree for a receive expression.
+
+tree
+Receive_expression::do_get_tree(Translate_context* context)
+{
+  Channel_type* channel_type = this->channel_->type()->channel_type();
+  if (channel_type == NULL)
+    {
+      gcc_assert(this->channel_->type()->is_error_type());
+      return error_mark_node;
+    }
+  Type* element_type = channel_type->element_type();
+  tree element_type_tree = element_type->get_tree(context->gogo());
+
+  tree channel = this->channel_->get_tree(context);
+  if (element_type_tree == error_mark_node || channel == error_mark_node)
+    return error_mark_node;
+
+  return Gogo::receive_from_channel(element_type_tree, channel,
+				    this->for_select_, this->location());
+}
+
+// Make a receive expression.
+
+Receive_expression*
+Expression::make_receive(Expression* channel, source_location location)
+{
+  return new Receive_expression(channel, location);
+}
+
+// Class Send_expression.
+
+// Traversal.
+
+int
+Send_expression::do_traverse(Traverse* traverse)
+{
+  if (Expression::traverse(&this->channel_, traverse) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return Expression::traverse(&this->val_, traverse);
+}
+
+// Get the type.
+
+Type*
+Send_expression::do_type()
+{
+  if (this->is_value_discarded_)
+    return Type::make_void_type();
+  else
+    return Type::lookup_bool_type();
+}
+
+// Set types.
+
+void
+Send_expression::do_determine_type(const Type_context*)
+{
+  this->channel_->determine_type_no_context();
+
+  Type* type = this->channel_->type();
+  Type_context subcontext;
+  if (type->channel_type() != NULL)
+    subcontext.type = type->channel_type()->element_type();
+  this->val_->determine_type(&subcontext);
+}
+
+// Check types.
+
+void
+Send_expression::do_check_types(Gogo*)
+{
+  Type* type = this->channel_->type();
+  if (type->is_error_type())
+    {
+      this->set_is_error();
+      return;
+    }
+  Channel_type* channel_type = type->channel_type();
+  if (channel_type == NULL)
+    {
+      error_at(this->location(), "left operand of %<<-%> must be channel");
+      this->set_is_error();
+      return;
+    }
+  Type* element_type = channel_type->element_type();
+  if (element_type != NULL
+      && !Type::are_assignable(element_type, this->val_->type(), NULL))
+    {
+      this->report_error(_("incompatible types in send"));
+      return;
+    }
+  if (!channel_type->may_send())
+    {
+      this->report_error(_("invalid send on receive-only channel"));
+      return;
+    }
+}
+
+// Get a tree for a send expression.
+
+tree
+Send_expression::do_get_tree(Translate_context* context)
+{
+  tree channel = this->channel_->get_tree(context);
+  tree val = this->val_->get_tree(context);
+  if (channel == error_mark_node || val == error_mark_node)
+    return error_mark_node;
+  Channel_type* channel_type = this->channel_->type()->channel_type();
+  val = Expression::convert_for_assignment(context,
+					   channel_type->element_type(),
+					   this->val_->type(),
+					   val,
+					   this->location());
+  return Gogo::send_on_channel(channel, val, this->is_value_discarded_,
+			       this->for_select_, this->location());
+}
+
+// Make a send expression
+
+Send_expression*
+Expression::make_send(Expression* channel, Expression* val,
+		      source_location location)
+{
+  return new Send_expression(channel, val, location);
+}
+
+// An expression which evaluates to a pointer to the type descriptor
+// of a type.
+
+class Type_descriptor_expression : public Expression
+{
+ public:
+  Type_descriptor_expression(Type* type, source_location location)
+    : Expression(EXPRESSION_TYPE_DESCRIPTOR, location),
+      type_(type)
+  { }
+
+ protected:
+  Type*
+  do_type()
+  { return Type::make_type_descriptor_ptr_type(); }
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  Expression*
+  do_copy()
+  { return this; }
+
+  tree
+  do_get_tree(Translate_context* context)
+  { return this->type_->type_descriptor_pointer(context->gogo()); }
+
+ private:
+  // The type for which this is the descriptor.
+  Type* type_;
+};
+
+// Make a type descriptor expression.
+
+Expression*
+Expression::make_type_descriptor(Type* type, source_location location)
+{
+  return new Type_descriptor_expression(type, location);
+}
+
+// An expression which evaluates to some characteristic of a type.
+// This is only used to initialize fields of a type descriptor.  Using
+// a new expression class is slightly inefficient but gives us a good
+// separation between the frontend and the middle-end with regard to
+// how types are laid out.
+
+class Type_info_expression : public Expression
+{
+ public:
+  Type_info_expression(Type* type, Type_info type_info)
+    : Expression(EXPRESSION_TYPE_INFO, BUILTINS_LOCATION),
+      type_(type), type_info_(type_info)
+  { }
+
+ protected:
+  Type*
+  do_type();
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  Expression*
+  do_copy()
+  { return this; }
+
+  tree
+  do_get_tree(Translate_context* context);
+
+ private:
+  // The type for which we are getting information.
+  Type* type_;
+  // What information we want.
+  Type_info type_info_;
+};
+
+// The type is chosen to match what the type descriptor struct
+// expects.
+
+Type*
+Type_info_expression::do_type()
+{
+  switch (this->type_info_)
+    {
+    case TYPE_INFO_SIZE:
+      return Type::lookup_integer_type("uintptr");
+    case TYPE_INFO_ALIGNMENT:
+    case TYPE_INFO_FIELD_ALIGNMENT:
+      return Type::lookup_integer_type("uint8");
+    default:
+      gcc_unreachable();
+    }
+}
+
+// Return type information in GENERIC.
+
+tree
+Type_info_expression::do_get_tree(Translate_context* context)
+{
+  tree type_tree = this->type_->get_tree(context->gogo());
+  if (type_tree == error_mark_node)
+    return error_mark_node;
+
+  tree val_type_tree = this->type()->get_tree(context->gogo());
+  gcc_assert(val_type_tree != error_mark_node);
+
+  if (this->type_info_ == TYPE_INFO_SIZE)
+    return fold_convert_loc(BUILTINS_LOCATION, val_type_tree,
+			    TYPE_SIZE_UNIT(type_tree));
+  else
+    {
+      unsigned int val;
+      if (this->type_info_ == TYPE_INFO_ALIGNMENT)
+	val = go_type_alignment(type_tree);
+      else
+	val = go_field_alignment(type_tree);
+      return build_int_cstu(val_type_tree, val);
+    }
+}
+
+// Make a type info expression.
+
+Expression*
+Expression::make_type_info(Type* type, Type_info type_info)
+{
+  return new Type_info_expression(type, type_info);
+}
+
+// An expression which evaluates to the offset of a field within a
+// struct.  This, like Type_info_expression, q.v., is only used to
+// initialize fields of a type descriptor.
+
+class Struct_field_offset_expression : public Expression
+{
+ public:
+  Struct_field_offset_expression(Struct_type* type, const Struct_field* field)
+    : Expression(EXPRESSION_STRUCT_FIELD_OFFSET, BUILTINS_LOCATION),
+      type_(type), field_(field)
+  { }
+
+ protected:
+  Type*
+  do_type()
+  { return Type::lookup_integer_type("uintptr"); }
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  Expression*
+  do_copy()
+  { return this; }
+
+  tree
+  do_get_tree(Translate_context* context);
+
+ private:
+  // The type of the struct.
+  Struct_type* type_;
+  // The field.
+  const Struct_field* field_;
+};
+
+// Return a struct field offset in GENERIC.
+
+tree
+Struct_field_offset_expression::do_get_tree(Translate_context* context)
+{
+  tree type_tree = this->type_->get_tree(context->gogo());
+  if (type_tree == error_mark_node)
+    return error_mark_node;
+
+  tree val_type_tree = this->type()->get_tree(context->gogo());
+  gcc_assert(val_type_tree != error_mark_node);
+
+  const Struct_field_list* fields = this->type_->fields();
+  tree struct_field_tree = TYPE_FIELDS(type_tree);
+  Struct_field_list::const_iterator p;
+  for (p = fields->begin();
+       p != fields->end();
+       ++p, struct_field_tree = DECL_CHAIN(struct_field_tree))
+    {
+      gcc_assert(struct_field_tree != NULL_TREE);
+      if (&*p == this->field_)
+	break;
+    }
+  gcc_assert(&*p == this->field_);
+
+  return fold_convert_loc(BUILTINS_LOCATION, val_type_tree,
+			  byte_position(struct_field_tree));
+}
+
+// Make an expression for a struct field offset.
+
+Expression*
+Expression::make_struct_field_offset(Struct_type* type,
+				     const Struct_field* field)
+{
+  return new Struct_field_offset_expression(type, field);
+}
+
+// An expression which evaluates to the address of an unnamed label.
+
+class Label_addr_expression : public Expression
+{
+ public:
+  Label_addr_expression(Label* label, source_location location)
+    : Expression(EXPRESSION_LABEL_ADDR, location),
+      label_(label)
+  { }
+
+ protected:
+  Type*
+  do_type()
+  { return Type::make_pointer_type(Type::make_void_type()); }
+
+  void
+  do_determine_type(const Type_context*)
+  { }
+
+  Expression*
+  do_copy()
+  { return new Label_addr_expression(this->label_, this->location()); }
+
+  tree
+  do_get_tree(Translate_context*)
+  { return this->label_->get_addr(this->location()); }
+
+ private:
+  // The label whose address we are taking.
+  Label* label_;
+};
+
+// Make an expression for the address of an unnamed label.
+
+Expression*
+Expression::make_label_addr(Label* label, source_location location)
+{
+  return new Label_addr_expression(label, location);
+}
+
+// Import an expression.  This comes at the end in order to see the
+// various class definitions.
+
+Expression*
+Expression::import_expression(Import* imp)
+{
+  int c = imp->peek_char();
+  if (imp->match_c_string("- ")
+      || imp->match_c_string("! ")
+      || imp->match_c_string("^ "))
+    return Unary_expression::do_import(imp);
+  else if (c == '(')
+    return Binary_expression::do_import(imp);
+  else if (imp->match_c_string("true")
+	   || imp->match_c_string("false"))
+    return Boolean_expression::do_import(imp);
+  else if (c == '"')
+    return String_expression::do_import(imp);
+  else if (c == '-' || (c >= '0' && c <= '9'))
+    {
+      // This handles integers, floats and complex constants.
+      return Integer_expression::do_import(imp);
+    }
+  else if (imp->match_c_string("nil"))
+    return Nil_expression::do_import(imp);
+  else if (imp->match_c_string("convert"))
+    return Type_conversion_expression::do_import(imp);
+  else
+    {
+      error_at(imp->location(), "import error: expected expression");
+      return Expression::make_error(imp->location());
+    }
+}
+
+// Class Expression_list.
+
+// Traverse the list.
+
+int
+Expression_list::traverse(Traverse* traverse)
+{
+  for (Expression_list::iterator p = this->begin();
+       p != this->end();
+       ++p)
+    {
+      if (*p != NULL)
+	{
+	  if (Expression::traverse(&*p, traverse) == TRAVERSE_EXIT)
+	    return TRAVERSE_EXIT;
+	}
+    }
+  return TRAVERSE_CONTINUE;
+}
+
+// Copy the list.
+
+Expression_list*
+Expression_list::copy()
+{
+  Expression_list* ret = new Expression_list();
+  for (Expression_list::iterator p = this->begin();
+       p != this->end();
+       ++p)
+    {
+      if (*p == NULL)
+	ret->push_back(NULL);
+      else
+	ret->push_back((*p)->copy());
+    }
+  return ret;
+}
+
+// Return whether an expression list has an error expression.
+
+bool
+Expression_list::contains_error() const
+{
+  for (Expression_list::const_iterator p = this->begin();
+       p != this->end();
+       ++p)
+    if (*p != NULL && (*p)->is_error_expression())
+      return true;
+  return false;
+}