Use backend interface for map descriptors.

[pf3gnuchains/gcc-fork.git] / gcc / go / gofrontend / types.cc

// types.cc -- Go frontend types.

// 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 "real.h"
#include "convert.h"

#ifndef ENABLE_BUILD_WITH_CXX
}
#endif

#include "go-c.h"
#include "gogo.h"
#include "operator.h"
#include "expressions.h"
#include "statements.h"
#include "export.h"
#include "import.h"
#include "backend.h"
#include "types.h"

// Class Type.

Type::Type(Type_classification classification)
  : classification_(classification), btype_(NULL), type_descriptor_var_(NULL)
{
}

Type::~Type()
{
}

// Get the base type for a type--skip names and forward declarations.

Type*
Type::base()
{
  switch (this->classification_)
    {
    case TYPE_NAMED:
      return this->named_type()->named_base();
    case TYPE_FORWARD:
      return this->forward_declaration_type()->real_type()->base();
    default:
      return this;
    }
}

const Type*
Type::base() const
{
  switch (this->classification_)
    {
    case TYPE_NAMED:
      return this->named_type()->named_base();
    case TYPE_FORWARD:
      return this->forward_declaration_type()->real_type()->base();
    default:
      return this;
    }
}

// Skip defined forward declarations.

Type*
Type::forwarded()
{
  Type* t = this;
  Forward_declaration_type* ftype = t->forward_declaration_type();
  while (ftype != NULL && ftype->is_defined())
    {
      t = ftype->real_type();
      ftype = t->forward_declaration_type();
    }
  return t;
}

const Type*
Type::forwarded() const
{
  const Type* t = this;
  const Forward_declaration_type* ftype = t->forward_declaration_type();
  while (ftype != NULL && ftype->is_defined())
    {
      t = ftype->real_type();
      ftype = t->forward_declaration_type();
    }
  return t;
}

// If this is a named type, return it.  Otherwise, return NULL.

Named_type*
Type::named_type()
{
  return this->forwarded()->convert_no_base<Named_type, TYPE_NAMED>();
}

const Named_type*
Type::named_type() const
{
  return this->forwarded()->convert_no_base<const Named_type, TYPE_NAMED>();
}

// Return true if this type is not defined.

bool
Type::is_undefined() const
{
  return this->forwarded()->forward_declaration_type() != NULL;
}

// Return true if this is a basic type: a type which is not composed
// of other types, and is not void.

bool
Type::is_basic_type() const
{
  switch (this->classification_)
    {
    case TYPE_INTEGER:
    case TYPE_FLOAT:
    case TYPE_COMPLEX:
    case TYPE_BOOLEAN:
    case TYPE_STRING:
    case TYPE_NIL:
      return true;

    case TYPE_ERROR:
    case TYPE_VOID:
    case TYPE_FUNCTION:
    case TYPE_POINTER:
    case TYPE_STRUCT:
    case TYPE_ARRAY:
    case TYPE_MAP:
    case TYPE_CHANNEL:
    case TYPE_INTERFACE:
      return false;

    case TYPE_NAMED:
    case TYPE_FORWARD:
      return this->base()->is_basic_type();

    default:
      go_unreachable();
    }
}

// Return true if this is an abstract type.

bool
Type::is_abstract() const
{
  switch (this->classification())
    {
    case TYPE_INTEGER:
      return this->integer_type()->is_abstract();
    case TYPE_FLOAT:
      return this->float_type()->is_abstract();
    case TYPE_COMPLEX:
      return this->complex_type()->is_abstract();
    case TYPE_STRING:
      return this->is_abstract_string_type();
    case TYPE_BOOLEAN:
      return this->is_abstract_boolean_type();
    default:
      return false;
    }
}

// Return a non-abstract version of an abstract type.

Type*
Type::make_non_abstract_type()
{
  go_assert(this->is_abstract());
  switch (this->classification())
    {
    case TYPE_INTEGER:
      return Type::lookup_integer_type("int");
    case TYPE_FLOAT:
      return Type::lookup_float_type("float64");
    case TYPE_COMPLEX:
      return Type::lookup_complex_type("complex128");
    case TYPE_STRING:
      return Type::lookup_string_type();
    case TYPE_BOOLEAN:
      return Type::lookup_bool_type();
    default:
      go_unreachable();
    }
}

// Return true if this is an error type.  Don't give an error if we
// try to dereference an undefined forwarding type, as this is called
// in the parser when the type may legitimately be undefined.

bool
Type::is_error_type() const
{
  const Type* t = this->forwarded();
  // Note that we return false for an undefined forward type.
  switch (t->classification_)
    {
    case TYPE_ERROR:
      return true;
    case TYPE_NAMED:
      return t->named_type()->is_named_error_type();
    default:
      return false;
    }
}

// If this is a pointer type, return the type to which it points.
// Otherwise, return NULL.

Type*
Type::points_to() const
{
  const Pointer_type* ptype = this->convert<const Pointer_type,
                                            TYPE_POINTER>();
  return ptype == NULL ? NULL : ptype->points_to();
}

// Return whether this is an open array type.

bool
Type::is_open_array_type() const
{
  return this->array_type() != NULL && this->array_type()->length() == NULL;
}

// Return whether this is the predeclared constant nil being used as a
// type.

bool
Type::is_nil_constant_as_type() const
{
  const Type* t = this->forwarded();
  if (t->forward_declaration_type() != NULL)
    {
      const Named_object* no = t->forward_declaration_type()->named_object();
      if (no->is_unknown())
        no = no->unknown_value()->real_named_object();
      if (no != NULL
          && no->is_const()
          && no->const_value()->expr()->is_nil_expression())
        return true;
    }
  return false;
}

// Traverse a type.

int
Type::traverse(Type* type, Traverse* traverse)
{
  go_assert((traverse->traverse_mask() & Traverse::traverse_types) != 0
             || (traverse->traverse_mask()
                 & Traverse::traverse_expressions) != 0);
  if (traverse->remember_type(type))
    {
      // We have already traversed this type.
      return TRAVERSE_CONTINUE;
    }
  if ((traverse->traverse_mask() & Traverse::traverse_types) != 0)
    {
      int t = traverse->type(type);
      if (t == TRAVERSE_EXIT)
        return TRAVERSE_EXIT;
      else if (t == TRAVERSE_SKIP_COMPONENTS)
        return TRAVERSE_CONTINUE;
    }
  // An array type has an expression which we need to traverse if
  // traverse_expressions is set.
  if (type->do_traverse(traverse) == TRAVERSE_EXIT)
    return TRAVERSE_EXIT;
  return TRAVERSE_CONTINUE;
}

// Default implementation for do_traverse for child class.

int
Type::do_traverse(Traverse*)
{
  return TRAVERSE_CONTINUE;
}

// Return whether two types are identical.  If ERRORS_ARE_IDENTICAL,
// then return true for all erroneous types; this is used to avoid
// cascading errors.  If REASON is not NULL, optionally set *REASON to
// the reason the types are not identical.

bool
Type::are_identical(const Type* t1, const Type* t2, bool errors_are_identical,
                    std::string* reason)
{
  if (t1 == NULL || t2 == NULL)
    {
      // Something is wrong.
      return errors_are_identical ? true : t1 == t2;
    }

  // Skip defined forward declarations.
  t1 = t1->forwarded();
  t2 = t2->forwarded();

  if (t1 == t2)
    return true;

  // An undefined forward declaration is an error.
  if (t1->forward_declaration_type() != NULL
      || t2->forward_declaration_type() != NULL)
    return errors_are_identical;

  // Avoid cascading errors with error types.
  if (t1->is_error_type() || t2->is_error_type())
    {
      if (errors_are_identical)
        return true;
      return t1->is_error_type() && t2->is_error_type();
    }

  // Get a good reason for the sink type.  Note that the sink type on
  // the left hand side of an assignment is handled in are_assignable.
  if (t1->is_sink_type() || t2->is_sink_type())
    {
      if (reason != NULL)
        *reason = "invalid use of _";
      return false;
    }

  // A named type is only identical to itself.
  if (t1->named_type() != NULL || t2->named_type() != NULL)
    return false;

  // Check type shapes.
  if (t1->classification() != t2->classification())
    return false;

  switch (t1->classification())
    {
    case TYPE_VOID:
    case TYPE_BOOLEAN:
    case TYPE_STRING:
    case TYPE_NIL:
      // These types are always identical.
      return true;

    case TYPE_INTEGER:
      return t1->integer_type()->is_identical(t2->integer_type());

    case TYPE_FLOAT:
      return t1->float_type()->is_identical(t2->float_type());

    case TYPE_COMPLEX:
      return t1->complex_type()->is_identical(t2->complex_type());

    case TYPE_FUNCTION:
      return t1->function_type()->is_identical(t2->function_type(),
                                               false,
                                               errors_are_identical,
                                               reason);

    case TYPE_POINTER:
      return Type::are_identical(t1->points_to(), t2->points_to(),
                                 errors_are_identical, reason);

    case TYPE_STRUCT:
      return t1->struct_type()->is_identical(t2->struct_type(),
                                             errors_are_identical);

    case TYPE_ARRAY:
      return t1->array_type()->is_identical(t2->array_type(),
                                            errors_are_identical);

    case TYPE_MAP:
      return t1->map_type()->is_identical(t2->map_type(),
                                          errors_are_identical);

    case TYPE_CHANNEL:
      return t1->channel_type()->is_identical(t2->channel_type(),
                                              errors_are_identical);

    case TYPE_INTERFACE:
      return t1->interface_type()->is_identical(t2->interface_type(),
                                                errors_are_identical);

    case TYPE_CALL_MULTIPLE_RESULT:
      if (reason != NULL)
        *reason = "invalid use of multiple value function call";
      return false;

    default:
      go_unreachable();
    }
}

// Return true if it's OK to have a binary operation with types LHS
// and RHS.  This is not used for shifts or comparisons.

bool
Type::are_compatible_for_binop(const Type* lhs, const Type* rhs)
{
  if (Type::are_identical(lhs, rhs, true, NULL))
    return true;

  // A constant of abstract bool type may be mixed with any bool type.
  if ((rhs->is_abstract_boolean_type() && lhs->is_boolean_type())
      || (lhs->is_abstract_boolean_type() && rhs->is_boolean_type()))
    return true;

  // A constant of abstract string type may be mixed with any string
  // type.
  if ((rhs->is_abstract_string_type() && lhs->is_string_type())
      || (lhs->is_abstract_string_type() && rhs->is_string_type()))
    return true;

  lhs = lhs->base();
  rhs = rhs->base();

  // A constant of abstract integer, float, or complex type may be
  // mixed with an integer, float, or complex type.
  if ((rhs->is_abstract()
       && (rhs->integer_type() != NULL
           || rhs->float_type() != NULL
           || rhs->complex_type() != NULL)
       && (lhs->integer_type() != NULL
           || lhs->float_type() != NULL
           || lhs->complex_type() != NULL))
      || (lhs->is_abstract()
          && (lhs->integer_type() != NULL
              || lhs->float_type() != NULL
              || lhs->complex_type() != NULL)
          && (rhs->integer_type() != NULL
              || rhs->float_type() != NULL
              || rhs->complex_type() != NULL)))
    return true;

  // The nil type may be compared to a pointer, an interface type, a
  // slice type, a channel type, a map type, or a function type.
  if (lhs->is_nil_type()
      && (rhs->points_to() != NULL
          || rhs->interface_type() != NULL
          || rhs->is_open_array_type()
          || rhs->map_type() != NULL
          || rhs->channel_type() != NULL
          || rhs->function_type() != NULL))
    return true;
  if (rhs->is_nil_type()
      && (lhs->points_to() != NULL
          || lhs->interface_type() != NULL
          || lhs->is_open_array_type()
          || lhs->map_type() != NULL
          || lhs->channel_type() != NULL
          || lhs->function_type() != NULL))
    return true;

  return false;
}

// Return true if a value with type RHS may be assigned to a variable
// with type LHS.  If CHECK_HIDDEN_FIELDS is true, check whether any
// hidden fields are modified.  If REASON is not NULL, set *REASON to
// the reason the types are not assignable.

bool
Type::are_assignable_check_hidden(const Type* lhs, const Type* rhs,
                                  bool check_hidden_fields,
                                  std::string* reason)
{
  // Do some checks first.  Make sure the types are defined.
  if (rhs != NULL
      && rhs->forwarded()->forward_declaration_type() == NULL
      && rhs->is_void_type())
    {
      if (reason != NULL)
        *reason = "non-value used as value";
      return false;
    }

  if (lhs != NULL && lhs->forwarded()->forward_declaration_type() == NULL)
    {
      // Any value may be assigned to the blank identifier.
      if (lhs->is_sink_type())
        return true;

      // All fields of a struct must be exported, or the assignment
      // must be in the same package.
      if (check_hidden_fields
          && rhs != NULL
          && rhs->forwarded()->forward_declaration_type() == NULL)
        {
          if (lhs->has_hidden_fields(NULL, reason)
              || rhs->has_hidden_fields(NULL, reason))
            return false;
        }
    }

  // Identical types are assignable.
  if (Type::are_identical(lhs, rhs, true, reason))
    return true;

  // The types are assignable if they have identical underlying types
  // and either LHS or RHS is not a named type.
  if (((lhs->named_type() != NULL && rhs->named_type() == NULL)
       || (rhs->named_type() != NULL && lhs->named_type() == NULL))
      && Type::are_identical(lhs->base(), rhs->base(), true, reason))
    return true;

  // The types are assignable if LHS is an interface type and RHS
  // implements the required methods.
  const Interface_type* lhs_interface_type = lhs->interface_type();
  if (lhs_interface_type != NULL)
    {
      if (lhs_interface_type->implements_interface(rhs, reason))
        return true;
      const Interface_type* rhs_interface_type = rhs->interface_type();
      if (rhs_interface_type != NULL
          && lhs_interface_type->is_compatible_for_assign(rhs_interface_type,
                                                          reason))
        return true;
    }

  // The type are assignable if RHS is a bidirectional channel type,
  // LHS is a channel type, they have identical element types, and
  // either LHS or RHS is not a named type.
  if (lhs->channel_type() != NULL
      && rhs->channel_type() != NULL
      && rhs->channel_type()->may_send()
      && rhs->channel_type()->may_receive()
      && (lhs->named_type() == NULL || rhs->named_type() == NULL)
      && Type::are_identical(lhs->channel_type()->element_type(),
                             rhs->channel_type()->element_type(),
                             true,
                             reason))
    return true;

  // The nil type may be assigned to a pointer, function, slice, map,
  // channel, or interface type.
  if (rhs->is_nil_type()
      && (lhs->points_to() != NULL
          || lhs->function_type() != NULL
          || lhs->is_open_array_type()
          || lhs->map_type() != NULL
          || lhs->channel_type() != NULL
          || lhs->interface_type() != NULL))
    return true;

  // An untyped numeric constant may be assigned to a numeric type if
  // it is representable in that type.
  if ((rhs->is_abstract()
       && (rhs->integer_type() != NULL
           || rhs->float_type() != NULL
           || rhs->complex_type() != NULL))
      && (lhs->integer_type() != NULL
          || lhs->float_type() != NULL
          || lhs->complex_type() != NULL))
    return true;

  // Give some better error messages.
  if (reason != NULL && reason->empty())
    {
      if (rhs->interface_type() != NULL)
        reason->assign(_("need explicit conversion"));
      else if (rhs->is_call_multiple_result_type())
        reason->assign(_("multiple value function call in "
                         "single value context"));
      else if (lhs->named_type() != NULL && rhs->named_type() != NULL)
        {
          size_t len = (lhs->named_type()->name().length()
                        + rhs->named_type()->name().length()
                        + 100);
          char* buf = new char[len];
          snprintf(buf, len, _("cannot use type %s as type %s"),
                   rhs->named_type()->message_name().c_str(),
                   lhs->named_type()->message_name().c_str());
          reason->assign(buf);
          delete[] buf;
        }
    }

  return false;
}

// Return true if a value with type RHS may be assigned to a variable
// with type LHS.  If REASON is not NULL, set *REASON to the reason
// the types are not assignable.

bool
Type::are_assignable(const Type* lhs, const Type* rhs, std::string* reason)
{
  return Type::are_assignable_check_hidden(lhs, rhs, true, reason);
}

// Like are_assignable but don't check for hidden fields.

bool
Type::are_assignable_hidden_ok(const Type* lhs, const Type* rhs,
                               std::string* reason)
{
  return Type::are_assignable_check_hidden(lhs, rhs, false, reason);
}

// Return true if a value with type RHS may be converted to type LHS.
// If REASON is not NULL, set *REASON to the reason the types are not
// convertible.

bool
Type::are_convertible(const Type* lhs, const Type* rhs, std::string* reason)
{
  // The types are convertible if they are assignable.
  if (Type::are_assignable(lhs, rhs, reason))
    return true;

  // The types are convertible if they have identical underlying
  // types.
  if ((lhs->named_type() != NULL || rhs->named_type() != NULL)
      && Type::are_identical(lhs->base(), rhs->base(), true, reason))
    return true;

  // The types are convertible if they are both unnamed pointer types
  // and their pointer base types have identical underlying types.
  if (lhs->named_type() == NULL
      && rhs->named_type() == NULL
      && lhs->points_to() != NULL
      && rhs->points_to() != NULL
      && (lhs->points_to()->named_type() != NULL
          || rhs->points_to()->named_type() != NULL)
      && Type::are_identical(lhs->points_to()->base(),
                             rhs->points_to()->base(),
                             true,
                             reason))
    return true;

  // Integer and floating point types are convertible to each other.
  if ((lhs->integer_type() != NULL || lhs->float_type() != NULL)
      && (rhs->integer_type() != NULL || rhs->float_type() != NULL))
    return true;

  // Complex types are convertible to each other.
  if (lhs->complex_type() != NULL && rhs->complex_type() != NULL)
    return true;

  // An integer, or []byte, or []int, may be converted to a string.
  if (lhs->is_string_type())
    {
      if (rhs->integer_type() != NULL)
        return true;
      if (rhs->is_open_array_type() && rhs->named_type() == NULL)
        {
          const Type* e = rhs->array_type()->element_type()->forwarded();
          if (e->integer_type() != NULL
              && (e == Type::lookup_integer_type("uint8")
                  || e == Type::lookup_integer_type("int")))
            return true;
        }
    }

  // A string may be converted to []byte or []int.
  if (rhs->is_string_type()
      && lhs->is_open_array_type()
      && lhs->named_type() == NULL)
    {
      const Type* e = lhs->array_type()->element_type()->forwarded();
      if (e->integer_type() != NULL
          && (e == Type::lookup_integer_type("uint8")
              || e == Type::lookup_integer_type("int")))
        return true;
    }

  // An unsafe.Pointer type may be converted to any pointer type or to
  // uintptr, and vice-versa.
  if (lhs->is_unsafe_pointer_type()
      && (rhs->points_to() != NULL
          || (rhs->integer_type() != NULL
              && rhs->forwarded() == Type::lookup_integer_type("uintptr"))))
    return true;
  if (rhs->is_unsafe_pointer_type()
      && (lhs->points_to() != NULL
          || (lhs->integer_type() != NULL
              && lhs->forwarded() == Type::lookup_integer_type("uintptr"))))
    return true;

  // Give a better error message.
  if (reason != NULL)
    {
      if (reason->empty())
        *reason = "invalid type conversion";
      else
        {
          std::string s = "invalid type conversion (";
          s += *reason;
          s += ')';
          *reason = s;
        }
    }

  return false;
}

// Return whether this type has any hidden fields.  This is only a
// possibility for a few types.

bool
Type::has_hidden_fields(const Named_type* within, std::string* reason) const
{
  switch (this->forwarded()->classification_)
    {
    case TYPE_NAMED:
      return this->named_type()->named_type_has_hidden_fields(reason);
    case TYPE_STRUCT:
      return this->struct_type()->struct_has_hidden_fields(within, reason);
    case TYPE_ARRAY:
      return this->array_type()->array_has_hidden_fields(within, reason);
    default:
      return false;
    }
}

// Return a hash code for the type to be used for method lookup.

unsigned int
Type::hash_for_method(Gogo* gogo) const
{
  unsigned int ret = 0;
  if (this->classification_ != TYPE_FORWARD)
    ret += this->classification_;
  return ret + this->do_hash_for_method(gogo);
}

// Default implementation of do_hash_for_method.  This is appropriate
// for types with no subfields.

unsigned int
Type::do_hash_for_method(Gogo*) const
{
  return 0;
}

// Return a hash code for a string, given a starting hash.

unsigned int
Type::hash_string(const std::string& s, unsigned int h)
{
  const char* p = s.data();
  size_t len = s.length();
  for (; len > 0; --len)
    {
      h ^= *p++;
      h*= 16777619;
    }
  return h;
}

// Default check for the expression passed to make.  Any type which
// may be used with make implements its own version of this.

bool
Type::do_check_make_expression(Expression_list*, source_location)
{
  go_unreachable();
}

// Return whether an expression has an integer value.  Report an error
// if not.  This is used when handling calls to the predeclared make
// function.

bool
Type::check_int_value(Expression* e, const char* errmsg,
                      source_location location)
{
  if (e->type()->integer_type() != NULL)
    return true;

  // Check for a floating point constant with integer value.
  mpfr_t fval;
  mpfr_init(fval);

  Type* dummy;
  if (e->float_constant_value(fval, &dummy) && mpfr_integer_p(fval))
    {
      mpz_t ival;
      mpz_init(ival);

      bool ok = false;

      mpfr_clear_overflow();
      mpfr_clear_erangeflag();
      mpfr_get_z(ival, fval, GMP_RNDN);
      if (!mpfr_overflow_p()
          && !mpfr_erangeflag_p()
          && mpz_sgn(ival) >= 0)
        {
          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);
          ok = mpz_cmp(ival, max) < 0;
          mpz_clear(max);
        }
      mpz_clear(ival);

      if (ok)
        {
          mpfr_clear(fval);
          return true;
        }
    }

  mpfr_clear(fval);

  error_at(location, "%s", errmsg);
  return false;
}

// A hash table mapping unnamed types to the backend representation of
// those types.

Type::Type_btypes Type::type_btypes;

// Return a tree representing this type.

Btype*
Type::get_backend(Gogo* gogo)
{
  if (this->btype_ != NULL)
    return this->btype_;

  if (this->forward_declaration_type() != NULL
      || this->named_type() != NULL)
    return this->get_btype_without_hash(gogo);

  if (this->is_error_type())
    return gogo->backend()->error_type();

  // To avoid confusing the backend, translate all identical Go types
  // to the same backend representation.  We use a hash table to do
  // that.  There is no need to use the hash table for named types, as
  // named types are only identical to themselves.

  std::pair<Type*, Btype*> val(this, NULL);
  std::pair<Type_btypes::iterator, bool> ins =
    Type::type_btypes.insert(val);
  if (!ins.second && ins.first->second != NULL)
    {
      if (gogo != NULL && gogo->named_types_are_converted())
        this->btype_ = ins.first->second;
      return ins.first->second;
    }

  Btype* bt = this->get_btype_without_hash(gogo);

  if (ins.first->second == NULL)
    ins.first->second = bt;
  else
    {
      // We have already created a backend representation for this
      // type.  This can happen when an unnamed type is defined using
      // a named type which in turns uses an identical unnamed type.
      // Use the tree we created earlier and ignore the one we just
      // built.
      bt = ins.first->second;
      if (gogo == NULL || !gogo->named_types_are_converted())
        return bt;
      this->btype_ = bt;
    }

  return bt;
}

// Return the backend representation for a type without looking in the
// hash table for identical types.  This is used for named types,
// since a named type is never identical to any other type.

Btype*
Type::get_btype_without_hash(Gogo* gogo)
{
  if (this->btype_ == NULL)
    {
      Btype* bt = this->do_get_backend(gogo);

      // For a recursive function or pointer type, we will temporarily
      // return a circular pointer type during the recursion.  We
      // don't want to record that for a forwarding type, as it may
      // confuse us later.
      if (this->forward_declaration_type() != NULL
          && gogo->backend()->is_circular_pointer_type(bt))
        return bt;

      if (gogo == NULL || !gogo->named_types_are_converted())
        return bt;

      this->btype_ = bt;
    }
  return this->btype_;
}

// Any type which supports the builtin make function must implement
// this.

tree
Type::do_make_expression_tree(Translate_context*, Expression_list*,
                              source_location)
{
  go_unreachable();
}

// Return a pointer to the type descriptor for this type.

tree
Type::type_descriptor_pointer(Gogo* gogo, source_location location)
{
  Type* t = this->forwarded();
  if (t->type_descriptor_var_ == NULL)
    {
      t->make_type_descriptor_var(gogo);
      go_assert(t->type_descriptor_var_ != NULL);
    }
  tree var_tree = var_to_tree(t->type_descriptor_var_);
  if (var_tree == error_mark_node)
    return error_mark_node;
  return build_fold_addr_expr_loc(location, var_tree);
}

// A mapping from unnamed types to type descriptor variables.

Type::Type_descriptor_vars Type::type_descriptor_vars;

// Build the type descriptor for this type.

void
Type::make_type_descriptor_var(Gogo* gogo)
{
  go_assert(this->type_descriptor_var_ == NULL);

  Named_type* nt = this->named_type();

  // We can have multiple instances of unnamed types, but we only want
  // to emit the type descriptor once.  We use a hash table.  This is
  // not necessary for named types, as they are unique, and we store
  // the type descriptor in the type itself.
  Bvariable** phash = NULL;
  if (nt == NULL)
    {
      Bvariable* bvnull = NULL;
      std::pair<Type_descriptor_vars::iterator, bool> ins =
        Type::type_descriptor_vars.insert(std::make_pair(this, bvnull));
      if (!ins.second)
        {
          // We've already build a type descriptor for this type.
          this->type_descriptor_var_ = ins.first->second;
          return;
        }
      phash = &ins.first->second;
    }

  std::string var_name;
  if (nt == NULL)
    var_name = this->unnamed_type_descriptor_var_name(gogo);
  else
    var_name = this->type_descriptor_var_name(gogo);

  // Build the contents of the type descriptor.
  Expression* initializer = this->do_type_descriptor(gogo, NULL);

  Btype* initializer_btype = initializer->type()->get_backend(gogo);

  // See if this type descriptor is defined in a different package.
  bool is_defined_elsewhere = false;
  if (nt != NULL)
    {
      if (nt->named_object()->package() != NULL)
        {
          // This is a named type defined in a different package.  The
          // type descriptor should be defined in that package.
          is_defined_elsewhere = true;
        }
    }
  else
    {
      if (this->points_to() != NULL
          && this->points_to()->named_type() != NULL
          && this->points_to()->named_type()->named_object()->package() != NULL)
        {
          // This is an unnamed pointer to a named type defined in a
          // different package.  The descriptor should be defined in
          // that package.
          is_defined_elsewhere = true;
        }
    }

  source_location loc = nt == NULL ? BUILTINS_LOCATION : nt->location();

  if (is_defined_elsewhere)
    {
      this->type_descriptor_var_ =
        gogo->backend()->immutable_struct_reference(var_name,
                                                    initializer_btype,
                                                    loc);
      if (phash != NULL)
        *phash = this->type_descriptor_var_;
      return;
    }

  // See if this type descriptor can appear in multiple packages.
  bool is_common = false;
  if (nt != NULL)
    {
      // We create the descriptor for a builtin type whenever we need
      // it.
      is_common = nt->is_builtin();
    }
  else
    {
      // This is an unnamed type.  The descriptor could be defined in
      // any package where it is needed, and the linker will pick one
      // descriptor to keep.
      is_common = true;
    }

  // We are going to build the type descriptor in this package.  We
  // must create the variable before we convert the initializer to the
  // backend representation, because the initializer may refer to the
  // type descriptor of this type.  By setting type_descriptor_var_ we
  // ensure that type_descriptor_pointer will work if called while
  // converting INITIALIZER.

  this->type_descriptor_var_ =
    gogo->backend()->immutable_struct(var_name, is_common, initializer_btype,
                                      loc);
  if (phash != NULL)
    *phash = this->type_descriptor_var_;

  Translate_context context(gogo, NULL, NULL, NULL);
  context.set_is_const();
  Bexpression* binitializer = tree_to_expr(initializer->get_tree(&context));

  gogo->backend()->immutable_struct_set_init(this->type_descriptor_var_,
                                             var_name, is_common,
                                             initializer_btype, loc,
                                             binitializer);
}

// Return the name of the type descriptor variable for an unnamed
// type.

std::string
Type::unnamed_type_descriptor_var_name(Gogo* gogo)
{
  return "__go_td_" + this->mangled_name(gogo);
}

// Return the name of the type descriptor variable for a named type.

std::string
Type::type_descriptor_var_name(Gogo* gogo)
{
  Named_type* nt = this->named_type();
  Named_object* no = nt->named_object();
  const Named_object* in_function = nt->in_function();
  std::string ret = "__go_tdn_";
  if (nt->is_builtin())
    go_assert(in_function == NULL);
  else
    {
      const std::string& unique_prefix(no->package() == NULL
                                       ? gogo->unique_prefix()
                                       : no->package()->unique_prefix());
      const std::string& package_name(no->package() == NULL
                                      ? gogo->package_name()
                                      : no->package()->name());
      ret.append(unique_prefix);
      ret.append(1, '.');
      ret.append(package_name);
      ret.append(1, '.');
      if (in_function != NULL)
        {
          ret.append(Gogo::unpack_hidden_name(in_function->name()));
          ret.append(1, '.');
        }
    }
  ret.append(no->name());
  return ret;
}

// Return a composite literal for a type descriptor.

Expression*
Type::type_descriptor(Gogo* gogo, Type* type)
{
  return type->do_type_descriptor(gogo, NULL);
}

// Return a composite literal for a type descriptor with a name.

Expression*
Type::named_type_descriptor(Gogo* gogo, Type* type, Named_type* name)
{
  go_assert(name != NULL && type->named_type() != name);
  return type->do_type_descriptor(gogo, name);
}

// Make a builtin struct type from a list of fields.  The fields are
// pairs of a name and a type.

Struct_type*
Type::make_builtin_struct_type(int nfields, ...)
{
  va_list ap;
  va_start(ap, nfields);

  source_location bloc = BUILTINS_LOCATION;
  Struct_field_list* sfl = new Struct_field_list();
  for (int i = 0; i < nfields; i++)
    {
      const char* field_name = va_arg(ap, const char *);
      Type* type = va_arg(ap, Type*);
      sfl->push_back(Struct_field(Typed_identifier(field_name, type, bloc)));
    }

  va_end(ap);

  return Type::make_struct_type(sfl, bloc);
}

// A list of builtin named types.

std::vector<Named_type*> Type::named_builtin_types;

// Make a builtin named type.

Named_type*
Type::make_builtin_named_type(const char* name, Type* type)
{
  source_location bloc = BUILTINS_LOCATION;
  Named_object* no = Named_object::make_type(name, NULL, type, bloc);
  Named_type* ret = no->type_value();
  Type::named_builtin_types.push_back(ret);
  return ret;
}

// Convert the named builtin types.

void
Type::convert_builtin_named_types(Gogo* gogo)
{
  for (std::vector<Named_type*>::const_iterator p =
         Type::named_builtin_types.begin();
       p != Type::named_builtin_types.end();
       ++p)
    {
      bool r = (*p)->verify();
      go_assert(r);
      (*p)->convert(gogo);
    }
}

// Return the type of a type descriptor.  We should really tie this to
// runtime.Type rather than copying it.  This must match commonType in
// libgo/go/runtime/type.go.

Type*
Type::make_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      source_location bloc = BUILTINS_LOCATION;

      Type* uint8_type = Type::lookup_integer_type("uint8");
      Type* uint32_type = Type::lookup_integer_type("uint32");
      Type* uintptr_type = Type::lookup_integer_type("uintptr");
      Type* string_type = Type::lookup_string_type();
      Type* pointer_string_type = Type::make_pointer_type(string_type);

      // This is an unnamed version of unsafe.Pointer.  Perhaps we
      // should use the named version instead, although that would
      // require us to create the unsafe package if it has not been
      // imported.  It probably doesn't matter.
      Type* void_type = Type::make_void_type();
      Type* unsafe_pointer_type = Type::make_pointer_type(void_type);

      // Forward declaration for the type descriptor type.
      Named_object* named_type_descriptor_type =
        Named_object::make_type_declaration("commonType", NULL, bloc);
      Type* ft = Type::make_forward_declaration(named_type_descriptor_type);
      Type* pointer_type_descriptor_type = Type::make_pointer_type(ft);

      // The type of a method on a concrete type.
      Struct_type* method_type =
        Type::make_builtin_struct_type(5,
                                       "name", pointer_string_type,
                                       "pkgPath", pointer_string_type,
                                       "mtyp", pointer_type_descriptor_type,
                                       "typ", pointer_type_descriptor_type,
                                       "tfn", unsafe_pointer_type);
      Named_type* named_method_type =
        Type::make_builtin_named_type("method", method_type);

      // Information for types with a name or methods.
      Type* slice_named_method_type =
        Type::make_array_type(named_method_type, NULL);
      Struct_type* uncommon_type =
        Type::make_builtin_struct_type(3,
                                       "name", pointer_string_type,
                                       "pkgPath", pointer_string_type,
                                       "methods", slice_named_method_type);
      Named_type* named_uncommon_type =
        Type::make_builtin_named_type("uncommonType", uncommon_type);

      Type* pointer_uncommon_type =
        Type::make_pointer_type(named_uncommon_type);

      // The type descriptor type.

      Typed_identifier_list* params = new Typed_identifier_list();
      params->push_back(Typed_identifier("", unsafe_pointer_type, bloc));
      params->push_back(Typed_identifier("", uintptr_type, bloc));

      Typed_identifier_list* results = new Typed_identifier_list();
      results->push_back(Typed_identifier("", uintptr_type, bloc));

      Type* hashfn_type = Type::make_function_type(NULL, params, results, bloc);

      params = new Typed_identifier_list();
      params->push_back(Typed_identifier("", unsafe_pointer_type, bloc));
      params->push_back(Typed_identifier("", unsafe_pointer_type, bloc));
      params->push_back(Typed_identifier("", uintptr_type, bloc));

      results = new Typed_identifier_list();
      results->push_back(Typed_identifier("", Type::lookup_bool_type(), bloc));

      Type* equalfn_type = Type::make_function_type(NULL, params, results,
                                                    bloc);

      Struct_type* type_descriptor_type =
        Type::make_builtin_struct_type(10,
                                       "Kind", uint8_type,
                                       "align", uint8_type,
                                       "fieldAlign", uint8_type,
                                       "size", uintptr_type,
                                       "hash", uint32_type,
                                       "hashfn", hashfn_type,
                                       "equalfn", equalfn_type,
                                       "string", pointer_string_type,
                                       "", pointer_uncommon_type,
                                       "ptrToThis",
                                       pointer_type_descriptor_type);

      Named_type* named = Type::make_builtin_named_type("commonType",
                                                        type_descriptor_type);

      named_type_descriptor_type->set_type_value(named);

      ret = named;
    }

  return ret;
}

// Make the type of a pointer to a type descriptor as represented in
// Go.

Type*
Type::make_type_descriptor_ptr_type()
{
  static Type* ret;
  if (ret == NULL)
    ret = Type::make_pointer_type(Type::make_type_descriptor_type());
  return ret;
}

// Return the names of runtime functions which compute a hash code for
// this type and which compare whether two values of this type are
// equal.

void
Type::type_functions(const char** hash_fn, const char** equal_fn) const
{
  switch (this->base()->classification())
    {
    case Type::TYPE_ERROR:
    case Type::TYPE_VOID:
    case Type::TYPE_NIL:
      // These types can not be hashed or compared.
      *hash_fn = "__go_type_hash_error";
      *equal_fn = "__go_type_equal_error";
      break;

    case Type::TYPE_BOOLEAN:
    case Type::TYPE_INTEGER:
    case Type::TYPE_FLOAT:
    case Type::TYPE_COMPLEX:
    case Type::TYPE_POINTER:
    case Type::TYPE_FUNCTION:
    case Type::TYPE_MAP:
    case Type::TYPE_CHANNEL:
      *hash_fn = "__go_type_hash_identity";
      *equal_fn = "__go_type_equal_identity";
      break;

    case Type::TYPE_STRING:
      *hash_fn = "__go_type_hash_string";
      *equal_fn = "__go_type_equal_string";
      break;

    case Type::TYPE_STRUCT:
    case Type::TYPE_ARRAY:
      // These types can not be hashed or compared.
      *hash_fn = "__go_type_hash_error";
      *equal_fn = "__go_type_equal_error";
      break;

    case Type::TYPE_INTERFACE:
      if (this->interface_type()->is_empty())
        {
          *hash_fn = "__go_type_hash_empty_interface";
          *equal_fn = "__go_type_equal_empty_interface";
        }
      else
        {
          *hash_fn = "__go_type_hash_interface";
          *equal_fn = "__go_type_equal_interface";
        }
      break;

    case Type::TYPE_NAMED:
    case Type::TYPE_FORWARD:
      go_unreachable();

    default:
      go_unreachable();
    }
}

// Return a composite literal for the type descriptor for a plain type
// of kind RUNTIME_TYPE_KIND named NAME.

Expression*
Type::type_descriptor_constructor(Gogo* gogo, int runtime_type_kind,
                                  Named_type* name, const Methods* methods,
                                  bool only_value_methods)
{
  source_location bloc = BUILTINS_LOCATION;

  Type* td_type = Type::make_type_descriptor_type();
  const Struct_field_list* fields = td_type->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(9);

  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->field_name() == "Kind");
  mpz_t iv;
  mpz_init_set_ui(iv, runtime_type_kind);
  vals->push_back(Expression::make_integer(&iv, p->type(), bloc));

  ++p;
  go_assert(p->field_name() == "align");
  Expression::Type_info type_info = Expression::TYPE_INFO_ALIGNMENT;
  vals->push_back(Expression::make_type_info(this, type_info));

  ++p;
  go_assert(p->field_name() == "fieldAlign");
  type_info = Expression::TYPE_INFO_FIELD_ALIGNMENT;
  vals->push_back(Expression::make_type_info(this, type_info));

  ++p;
  go_assert(p->field_name() == "size");
  type_info = Expression::TYPE_INFO_SIZE;
  vals->push_back(Expression::make_type_info(this, type_info));

  ++p;
  go_assert(p->field_name() == "hash");
  mpz_set_ui(iv, this->hash_for_method(gogo));
  vals->push_back(Expression::make_integer(&iv, p->type(), bloc));

  const char* hash_fn;
  const char* equal_fn;
  this->type_functions(&hash_fn, &equal_fn);

  ++p;
  go_assert(p->field_name() == "hashfn");
  Function_type* fntype = p->type()->function_type();
  Named_object* no = Named_object::make_function_declaration(hash_fn, NULL,
                                                             fntype,
                                                             bloc);
  no->func_declaration_value()->set_asm_name(hash_fn);
  vals->push_back(Expression::make_func_reference(no, NULL, bloc));

  ++p;
  go_assert(p->field_name() == "equalfn");
  fntype = p->type()->function_type();
  no = Named_object::make_function_declaration(equal_fn, NULL, fntype, bloc);
  no->func_declaration_value()->set_asm_name(equal_fn);
  vals->push_back(Expression::make_func_reference(no, NULL, bloc));

  ++p;
  go_assert(p->field_name() == "string");
  Expression* s = Expression::make_string((name != NULL
                                           ? name->reflection(gogo)
                                           : this->reflection(gogo)),
                                          bloc);
  vals->push_back(Expression::make_unary(OPERATOR_AND, s, bloc));

  ++p;
  go_assert(p->field_name() == "uncommonType");
  if (name == NULL && methods == NULL)
    vals->push_back(Expression::make_nil(bloc));
  else
    {
      if (methods == NULL)
        methods = name->methods();
      vals->push_back(this->uncommon_type_constructor(gogo,
                                                      p->type()->deref(),
                                                      name, methods,
                                                      only_value_methods));
    }

  ++p;
  go_assert(p->field_name() == "ptrToThis");
  if (name == NULL)
    vals->push_back(Expression::make_nil(bloc));
  else
    {
      Type* pt = Type::make_pointer_type(name);
      vals->push_back(Expression::make_type_descriptor(pt, bloc));
    }

  ++p;
  go_assert(p == fields->end());

  mpz_clear(iv);

  return Expression::make_struct_composite_literal(td_type, vals, bloc);
}

// Return a composite literal for the uncommon type information for
// this type.  UNCOMMON_STRUCT_TYPE is the type of the uncommon type
// struct.  If name is not NULL, it is the name of the type.  If
// METHODS is not NULL, it is the list of methods.  ONLY_VALUE_METHODS
// is true if only value methods should be included.  At least one of
// NAME and METHODS must not be NULL.

Expression*
Type::uncommon_type_constructor(Gogo* gogo, Type* uncommon_type,
                                Named_type* name, const Methods* methods,
                                bool only_value_methods) const
{
  source_location bloc = BUILTINS_LOCATION;

  const Struct_field_list* fields = uncommon_type->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(3);

  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->field_name() == "name");

  ++p;
  go_assert(p->field_name() == "pkgPath");

  if (name == NULL)
    {
      vals->push_back(Expression::make_nil(bloc));
      vals->push_back(Expression::make_nil(bloc));
    }
  else
    {
      Named_object* no = name->named_object();
      std::string n = Gogo::unpack_hidden_name(no->name());
      Expression* s = Expression::make_string(n, bloc);
      vals->push_back(Expression::make_unary(OPERATOR_AND, s, bloc));

      if (name->is_builtin())
        vals->push_back(Expression::make_nil(bloc));
      else
        {
          const Package* package = no->package();
          const std::string& unique_prefix(package == NULL
                                           ? gogo->unique_prefix()
                                           : package->unique_prefix());
          const std::string& package_name(package == NULL
                                          ? gogo->package_name()
                                          : package->name());
          n.assign(unique_prefix);
          n.append(1, '.');
          n.append(package_name);
          if (name->in_function() != NULL)
            {
              n.append(1, '.');
              n.append(Gogo::unpack_hidden_name(name->in_function()->name()));
            }
          s = Expression::make_string(n, bloc);
          vals->push_back(Expression::make_unary(OPERATOR_AND, s, bloc));
        }
    }

  ++p;
  go_assert(p->field_name() == "methods");
  vals->push_back(this->methods_constructor(gogo, p->type(), methods,
                                            only_value_methods));

  ++p;
  go_assert(p == fields->end());

  Expression* r = Expression::make_struct_composite_literal(uncommon_type,
                                                            vals, bloc);
  return Expression::make_unary(OPERATOR_AND, r, bloc);
}

// Sort methods by name.

class Sort_methods
{
 public:
  bool
  operator()(const std::pair<std::string, const Method*>& m1,
             const std::pair<std::string, const Method*>& m2) const
  { return m1.first < m2.first; }
};

// Return a composite literal for the type method table for this type.
// METHODS_TYPE is the type of the table, and is a slice type.
// METHODS is the list of methods.  If ONLY_VALUE_METHODS is true,
// then only value methods are used.

Expression*
Type::methods_constructor(Gogo* gogo, Type* methods_type,
                          const Methods* methods,
                          bool only_value_methods) const
{
  source_location bloc = BUILTINS_LOCATION;

  std::vector<std::pair<std::string, const Method*> > smethods;
  if (methods != NULL)
    {
      smethods.reserve(methods->count());
      for (Methods::const_iterator p = methods->begin();
           p != methods->end();
           ++p)
        {
          if (p->second->is_ambiguous())
            continue;
          if (only_value_methods && !p->second->is_value_method())
            continue;
          smethods.push_back(std::make_pair(p->first, p->second));
        }
    }

  if (smethods.empty())
    return Expression::make_slice_composite_literal(methods_type, NULL, bloc);

  std::sort(smethods.begin(), smethods.end(), Sort_methods());

  Type* method_type = methods_type->array_type()->element_type();

  Expression_list* vals = new Expression_list();
  vals->reserve(smethods.size());
  for (std::vector<std::pair<std::string, const Method*> >::const_iterator p
         = smethods.begin();
       p != smethods.end();
       ++p)
    vals->push_back(this->method_constructor(gogo, method_type, p->first,
                                             p->second, only_value_methods));

  return Expression::make_slice_composite_literal(methods_type, vals, bloc);
}

// Return a composite literal for a single method.  METHOD_TYPE is the
// type of the entry.  METHOD_NAME is the name of the method and M is
// the method information.

Expression*
Type::method_constructor(Gogo*, Type* method_type,
                         const std::string& method_name,
                         const Method* m,
                         bool only_value_methods) const
{
  source_location bloc = BUILTINS_LOCATION;

  const Struct_field_list* fields = method_type->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(5);

  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->field_name() == "name");
  const std::string n = Gogo::unpack_hidden_name(method_name);
  Expression* s = Expression::make_string(n, bloc);
  vals->push_back(Expression::make_unary(OPERATOR_AND, s, bloc));

  ++p;
  go_assert(p->field_name() == "pkgPath");
  if (!Gogo::is_hidden_name(method_name))
    vals->push_back(Expression::make_nil(bloc));
  else
    {
      s = Expression::make_string(Gogo::hidden_name_prefix(method_name), bloc);
      vals->push_back(Expression::make_unary(OPERATOR_AND, s, bloc));
    }

  Named_object* no = (m->needs_stub_method()
                      ? m->stub_object()
                      : m->named_object());

  Function_type* mtype;
  if (no->is_function())
    mtype = no->func_value()->type();
  else
    mtype = no->func_declaration_value()->type();
  go_assert(mtype->is_method());
  Type* nonmethod_type = mtype->copy_without_receiver();

  ++p;
  go_assert(p->field_name() == "mtyp");
  vals->push_back(Expression::make_type_descriptor(nonmethod_type, bloc));

  ++p;
  go_assert(p->field_name() == "typ");
  if (!only_value_methods && m->is_value_method())
    {
      // This is a value method on a pointer type.  Change the type of
      // the method to use a pointer receiver.  The implementation
      // always uses a pointer receiver anyhow.
      Type* rtype = mtype->receiver()->type();
      Type* prtype = Type::make_pointer_type(rtype);
      Typed_identifier* receiver =
        new Typed_identifier(mtype->receiver()->name(), prtype,
                             mtype->receiver()->location());
      mtype = Type::make_function_type(receiver,
                                       (mtype->parameters() == NULL
                                        ? NULL
                                        : mtype->parameters()->copy()),
                                       (mtype->results() == NULL
                                        ? NULL
                                        : mtype->results()->copy()),
                                       mtype->location());
    }
  vals->push_back(Expression::make_type_descriptor(mtype, bloc));

  ++p;
  go_assert(p->field_name() == "tfn");
  vals->push_back(Expression::make_func_reference(no, NULL, bloc));

  ++p;
  go_assert(p == fields->end());

  return Expression::make_struct_composite_literal(method_type, vals, bloc);
}

// Return a composite literal for the type descriptor of a plain type.
// RUNTIME_TYPE_KIND is the value of the kind field.  If NAME is not
// NULL, it is the name to use as well as the list of methods.

Expression*
Type::plain_type_descriptor(Gogo* gogo, int runtime_type_kind,
                            Named_type* name)
{
  return this->type_descriptor_constructor(gogo, runtime_type_kind,
                                           name, NULL, true);
}

// Return the type reflection string for this type.

std::string
Type::reflection(Gogo* gogo) const
{
  std::string ret;

  // The do_reflection virtual function should set RET to the
  // reflection string.
  this->do_reflection(gogo, &ret);

  return ret;
}

// Return a mangled name for the type.

std::string
Type::mangled_name(Gogo* gogo) const
{
  std::string ret;

  // The do_mangled_name virtual function should set RET to the
  // mangled name.  For a composite type it should append a code for
  // the composition and then call do_mangled_name on the components.
  this->do_mangled_name(gogo, &ret);

  return ret;
}

// Default function to export a type.

void
Type::do_export(Export*) const
{
  go_unreachable();
}

// Import a type.

Type*
Type::import_type(Import* imp)
{
  if (imp->match_c_string("("))
    return Function_type::do_import(imp);
  else if (imp->match_c_string("*"))
    return Pointer_type::do_import(imp);
  else if (imp->match_c_string("struct "))
    return Struct_type::do_import(imp);
  else if (imp->match_c_string("["))
    return Array_type::do_import(imp);
  else if (imp->match_c_string("map "))
    return Map_type::do_import(imp);
  else if (imp->match_c_string("chan "))
    return Channel_type::do_import(imp);
  else if (imp->match_c_string("interface"))
    return Interface_type::do_import(imp);
  else
    {
      error_at(imp->location(), "import error: expected type");
      return Type::make_error_type();
    }
}

// A type used to indicate a parsing error.  This exists to simplify
// later error detection.

class Error_type : public Type
{
 public:
  Error_type()
    : Type(TYPE_ERROR)
  { }

 protected:
  Btype*
  do_get_backend(Gogo* gogo)
  { return gogo->backend()->error_type(); }

  Expression*
  do_type_descriptor(Gogo*, Named_type*)
  { return Expression::make_error(BUILTINS_LOCATION); }

  void
  do_reflection(Gogo*, std::string*) const
  { go_assert(saw_errors()); }

  void
  do_mangled_name(Gogo*, std::string* ret) const
  { ret->push_back('E'); }
};

Type*
Type::make_error_type()
{
  static Error_type singleton_error_type;
  return &singleton_error_type;
}

// The void type.

class Void_type : public Type
{
 public:
  Void_type()
    : Type(TYPE_VOID)
  { }

 protected:
  Btype*
  do_get_backend(Gogo* gogo)
  { return gogo->backend()->void_type(); }

  Expression*
  do_type_descriptor(Gogo*, Named_type*)
  { go_unreachable(); }

  void
  do_reflection(Gogo*, std::string*) const
  { }

  void
  do_mangled_name(Gogo*, std::string* ret) const
  { ret->push_back('v'); }
};

Type*
Type::make_void_type()
{
  static Void_type singleton_void_type;
  return &singleton_void_type;
}

// The boolean type.

class Boolean_type : public Type
{
 public:
  Boolean_type()
    : Type(TYPE_BOOLEAN)
  { }

 protected:
  Btype*
  do_get_backend(Gogo* gogo)
  { return gogo->backend()->bool_type(); }

  Expression*
  do_type_descriptor(Gogo*, Named_type* name);

  // We should not be asked for the reflection string of a basic type.
  void
  do_reflection(Gogo*, std::string* ret) const
  { ret->append("bool"); }

  void
  do_mangled_name(Gogo*, std::string* ret) const
  { ret->push_back('b'); }
};

// Make the type descriptor.

Expression*
Boolean_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  if (name != NULL)
    return this->plain_type_descriptor(gogo, RUNTIME_TYPE_KIND_BOOL, name);
  else
    {
      Named_object* no = gogo->lookup_global("bool");
      go_assert(no != NULL);
      return Type::type_descriptor(gogo, no->type_value());
    }
}

Type*
Type::make_boolean_type()
{
  static Boolean_type boolean_type;
  return &boolean_type;
}

// The named type "bool".

static Named_type* named_bool_type;

// Get the named type "bool".

Named_type*
Type::lookup_bool_type()
{
  return named_bool_type;
}

// Make the named type "bool".

Named_type*
Type::make_named_bool_type()
{
  Type* bool_type = Type::make_boolean_type();
  Named_object* named_object = Named_object::make_type("bool", NULL,
                                                       bool_type,
                                                       BUILTINS_LOCATION);
  Named_type* named_type = named_object->type_value();
  named_bool_type = named_type;
  return named_type;
}

// Class Integer_type.

Integer_type::Named_integer_types Integer_type::named_integer_types;

// Create a new integer type.  Non-abstract integer types always have
// names.

Named_type*
Integer_type::create_integer_type(const char* name, bool is_unsigned,
                                  int bits, int runtime_type_kind)
{
  Integer_type* integer_type = new Integer_type(false, is_unsigned, bits,
                                                runtime_type_kind);
  std::string sname(name);
  Named_object* named_object = Named_object::make_type(sname, NULL,
                                                       integer_type,
                                                       BUILTINS_LOCATION);
  Named_type* named_type = named_object->type_value();
  std::pair<Named_integer_types::iterator, bool> ins =
    Integer_type::named_integer_types.insert(std::make_pair(sname, named_type));
  go_assert(ins.second);
  return named_type;
}

// Look up an existing integer type.

Named_type*
Integer_type::lookup_integer_type(const char* name)
{
  Named_integer_types::const_iterator p =
    Integer_type::named_integer_types.find(name);
  go_assert(p != Integer_type::named_integer_types.end());
  return p->second;
}

// Create a new abstract integer type.

Integer_type*
Integer_type::create_abstract_integer_type()
{
  static Integer_type* abstract_type;
  if (abstract_type == NULL)
    abstract_type = new Integer_type(true, false, INT_TYPE_SIZE,
                                     RUNTIME_TYPE_KIND_INT);
  return abstract_type;
}

// Integer type compatibility.

bool
Integer_type::is_identical(const Integer_type* t) const
{
  if (this->is_unsigned_ != t->is_unsigned_ || this->bits_ != t->bits_)
    return false;
  return this->is_abstract_ == t->is_abstract_;
}

// Hash code.

unsigned int
Integer_type::do_hash_for_method(Gogo*) const
{
  return ((this->bits_ << 4)
          + ((this->is_unsigned_ ? 1 : 0) << 8)
          + ((this->is_abstract_ ? 1 : 0) << 9));
}

// Convert an Integer_type to the backend representation.

Btype*
Integer_type::do_get_backend(Gogo* gogo)
{
  if (this->is_abstract_)
    {
      go_assert(saw_errors());
      return gogo->backend()->error_type();
    }
  return gogo->backend()->integer_type(this->is_unsigned_, this->bits_);
}

// The type descriptor for an integer type.  Integer types are always
// named.

Expression*
Integer_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  go_assert(name != NULL);
  return this->plain_type_descriptor(gogo, this->runtime_type_kind_, name);
}

// We should not be asked for the reflection string of a basic type.

void
Integer_type::do_reflection(Gogo*, std::string*) const
{
  go_assert(saw_errors());
}

// Mangled name.

void
Integer_type::do_mangled_name(Gogo*, std::string* ret) const
{
  char buf[100];
  snprintf(buf, sizeof buf, "i%s%s%de",
           this->is_abstract_ ? "a" : "",
           this->is_unsigned_ ? "u" : "",
           this->bits_);
  ret->append(buf);
}

// Make an integer type.

Named_type*
Type::make_integer_type(const char* name, bool is_unsigned, int bits,
                        int runtime_type_kind)
{
  return Integer_type::create_integer_type(name, is_unsigned, bits,
                                           runtime_type_kind);
}

// Make an abstract integer type.

Integer_type*
Type::make_abstract_integer_type()
{
  return Integer_type::create_abstract_integer_type();
}

// Look up an integer type.

Named_type*
Type::lookup_integer_type(const char* name)
{
  return Integer_type::lookup_integer_type(name);
}

// Class Float_type.

Float_type::Named_float_types Float_type::named_float_types;

// Create a new float type.  Non-abstract float types always have
// names.

Named_type*
Float_type::create_float_type(const char* name, int bits,
                              int runtime_type_kind)
{
  Float_type* float_type = new Float_type(false, bits, runtime_type_kind);
  std::string sname(name);
  Named_object* named_object = Named_object::make_type(sname, NULL, float_type,
                                                       BUILTINS_LOCATION);
  Named_type* named_type = named_object->type_value();
  std::pair<Named_float_types::iterator, bool> ins =
    Float_type::named_float_types.insert(std::make_pair(sname, named_type));
  go_assert(ins.second);
  return named_type;
}

// Look up an existing float type.

Named_type*
Float_type::lookup_float_type(const char* name)
{
  Named_float_types::const_iterator p =
    Float_type::named_float_types.find(name);
  go_assert(p != Float_type::named_float_types.end());
  return p->second;
}

// Create a new abstract float type.

Float_type*
Float_type::create_abstract_float_type()
{
  static Float_type* abstract_type;
  if (abstract_type == NULL)
    abstract_type = new Float_type(true, 64, RUNTIME_TYPE_KIND_FLOAT64);
  return abstract_type;
}

// Whether this type is identical with T.

bool
Float_type::is_identical(const Float_type* t) const
{
  if (this->bits_ != t->bits_)
    return false;
  return this->is_abstract_ == t->is_abstract_;
}

// Hash code.

unsigned int
Float_type::do_hash_for_method(Gogo*) const
{
  return (this->bits_ << 4) + ((this->is_abstract_ ? 1 : 0) << 8);
}

// Convert to the backend representation.

Btype*
Float_type::do_get_backend(Gogo* gogo)
{
  return gogo->backend()->float_type(this->bits_);
}

// The type descriptor for a float type.  Float types are always named.

Expression*
Float_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  go_assert(name != NULL);
  return this->plain_type_descriptor(gogo, this->runtime_type_kind_, name);
}

// We should not be asked for the reflection string of a basic type.

void
Float_type::do_reflection(Gogo*, std::string*) const
{
  go_assert(saw_errors());
}

// Mangled name.

void
Float_type::do_mangled_name(Gogo*, std::string* ret) const
{
  char buf[100];
  snprintf(buf, sizeof buf, "f%s%de",
           this->is_abstract_ ? "a" : "",
           this->bits_);
  ret->append(buf);
}

// Make a floating point type.

Named_type*
Type::make_float_type(const char* name, int bits, int runtime_type_kind)
{
  return Float_type::create_float_type(name, bits, runtime_type_kind);
}

// Make an abstract float type.

Float_type*
Type::make_abstract_float_type()
{
  return Float_type::create_abstract_float_type();
}

// Look up a float type.

Named_type*
Type::lookup_float_type(const char* name)
{
  return Float_type::lookup_float_type(name);
}

// Class Complex_type.

Complex_type::Named_complex_types Complex_type::named_complex_types;

// Create a new complex type.  Non-abstract complex types always have
// names.

Named_type*
Complex_type::create_complex_type(const char* name, int bits,
                                  int runtime_type_kind)
{
  Complex_type* complex_type = new Complex_type(false, bits,
                                                runtime_type_kind);
  std::string sname(name);
  Named_object* named_object = Named_object::make_type(sname, NULL,
                                                       complex_type,
                                                       BUILTINS_LOCATION);
  Named_type* named_type = named_object->type_value();
  std::pair<Named_complex_types::iterator, bool> ins =
    Complex_type::named_complex_types.insert(std::make_pair(sname,
                                                            named_type));
  go_assert(ins.second);
  return named_type;
}

// Look up an existing complex type.

Named_type*
Complex_type::lookup_complex_type(const char* name)
{
  Named_complex_types::const_iterator p =
    Complex_type::named_complex_types.find(name);
  go_assert(p != Complex_type::named_complex_types.end());
  return p->second;
}

// Create a new abstract complex type.

Complex_type*
Complex_type::create_abstract_complex_type()
{
  static Complex_type* abstract_type;
  if (abstract_type == NULL)
    abstract_type = new Complex_type(true, 128, RUNTIME_TYPE_KIND_COMPLEX128);
  return abstract_type;
}

// Whether this type is identical with T.

bool
Complex_type::is_identical(const Complex_type *t) const
{
  if (this->bits_ != t->bits_)
    return false;
  return this->is_abstract_ == t->is_abstract_;
}

// Hash code.

unsigned int
Complex_type::do_hash_for_method(Gogo*) const
{
  return (this->bits_ << 4) + ((this->is_abstract_ ? 1 : 0) << 8);
}

// Convert to the backend representation.

Btype*
Complex_type::do_get_backend(Gogo* gogo)
{
  return gogo->backend()->complex_type(this->bits_);
}

// The type descriptor for a complex type.  Complex types are always
// named.

Expression*
Complex_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  go_assert(name != NULL);
  return this->plain_type_descriptor(gogo, this->runtime_type_kind_, name);
}

// We should not be asked for the reflection string of a basic type.

void
Complex_type::do_reflection(Gogo*, std::string*) const
{
  go_assert(saw_errors());
}

// Mangled name.

void
Complex_type::do_mangled_name(Gogo*, std::string* ret) const
{
  char buf[100];
  snprintf(buf, sizeof buf, "c%s%de",
           this->is_abstract_ ? "a" : "",
           this->bits_);
  ret->append(buf);
}

// Make a complex type.

Named_type*
Type::make_complex_type(const char* name, int bits, int runtime_type_kind)
{
  return Complex_type::create_complex_type(name, bits, runtime_type_kind);
}

// Make an abstract complex type.

Complex_type*
Type::make_abstract_complex_type()
{
  return Complex_type::create_abstract_complex_type();
}

// Look up a complex type.

Named_type*
Type::lookup_complex_type(const char* name)
{
  return Complex_type::lookup_complex_type(name);
}

// Class String_type.

// Convert String_type to the backend representation.  A string is a
// struct with two fields: a pointer to the characters and a length.

Btype*
String_type::do_get_backend(Gogo* gogo)
{
  static Btype* backend_string_type;
  if (backend_string_type == NULL)
    {
      std::vector<Backend::Btyped_identifier> fields(2);

      Type* b = gogo->lookup_global("byte")->type_value();
      Type* pb = Type::make_pointer_type(b);
      fields[0].name = "__data";
      fields[0].btype = pb->get_backend(gogo);
      fields[0].location = UNKNOWN_LOCATION;

      Type* int_type = Type::lookup_integer_type("int");
      fields[1].name = "__length";
      fields[1].btype = int_type->get_backend(gogo);
      fields[1].location = UNKNOWN_LOCATION;

      backend_string_type = gogo->backend()->struct_type(fields);
    }
  return backend_string_type;
}

// Return a tree for the length of STRING.

tree
String_type::length_tree(Gogo*, tree string)
{
  tree string_type = TREE_TYPE(string);
  go_assert(TREE_CODE(string_type) == RECORD_TYPE);
  tree length_field = DECL_CHAIN(TYPE_FIELDS(string_type));
  go_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(length_field)),
                    "__length") == 0);
  return fold_build3(COMPONENT_REF, integer_type_node, string,
                     length_field, NULL_TREE);
}

// Return a tree for a pointer to the bytes of STRING.

tree
String_type::bytes_tree(Gogo*, tree string)
{
  tree string_type = TREE_TYPE(string);
  go_assert(TREE_CODE(string_type) == RECORD_TYPE);
  tree bytes_field = TYPE_FIELDS(string_type);
  go_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(bytes_field)),
                    "__data") == 0);
  return fold_build3(COMPONENT_REF, TREE_TYPE(bytes_field), string,
                     bytes_field, NULL_TREE);
}

// The type descriptor for the string type.

Expression*
String_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  if (name != NULL)
    return this->plain_type_descriptor(gogo, RUNTIME_TYPE_KIND_STRING, name);
  else
    {
      Named_object* no = gogo->lookup_global("string");
      go_assert(no != NULL);
      return Type::type_descriptor(gogo, no->type_value());
    }
}

// We should not be asked for the reflection string of a basic type.

void
String_type::do_reflection(Gogo*, std::string* ret) const
{
  ret->append("string");
}

// Mangled name of a string type.

void
String_type::do_mangled_name(Gogo*, std::string* ret) const
{
  ret->push_back('z');
}

// Make a string type.

Type*
Type::make_string_type()
{
  static String_type string_type;
  return &string_type;
}

// The named type "string".

static Named_type* named_string_type;

// Get the named type "string".

Named_type*
Type::lookup_string_type()
{
  return named_string_type;
}

// Make the named type string.

Named_type*
Type::make_named_string_type()
{
  Type* string_type = Type::make_string_type();
  Named_object* named_object = Named_object::make_type("string", NULL,
                                                       string_type,
                                                       BUILTINS_LOCATION);
  Named_type* named_type = named_object->type_value();
  named_string_type = named_type;
  return named_type;
}

// The sink type.  This is the type of the blank identifier _.  Any
// type may be assigned to it.

class Sink_type : public Type
{
 public:
  Sink_type()
    : Type(TYPE_SINK)
  { }

 protected:
  Btype*
  do_get_backend(Gogo*)
  { go_unreachable(); }

  Expression*
  do_type_descriptor(Gogo*, Named_type*)
  { go_unreachable(); }

  void
  do_reflection(Gogo*, std::string*) const
  { go_unreachable(); }

  void
  do_mangled_name(Gogo*, std::string*) const
  { go_unreachable(); }
};

// Make the sink type.

Type*
Type::make_sink_type()
{
  static Sink_type sink_type;
  return &sink_type;
}

// Class Function_type.

// Traversal.

int
Function_type::do_traverse(Traverse* traverse)
{
  if (this->receiver_ != NULL
      && Type::traverse(this->receiver_->type(), traverse) == TRAVERSE_EXIT)
    return TRAVERSE_EXIT;
  if (this->parameters_ != NULL
      && this->parameters_->traverse(traverse) == TRAVERSE_EXIT)
    return TRAVERSE_EXIT;
  if (this->results_ != NULL
      && this->results_->traverse(traverse) == TRAVERSE_EXIT)
    return TRAVERSE_EXIT;
  return TRAVERSE_CONTINUE;
}

// Returns whether T is a valid redeclaration of this type.  If this
// returns false, and REASON is not NULL, *REASON may be set to a
// brief explanation of why it returned false.

bool
Function_type::is_valid_redeclaration(const Function_type* t,
                                      std::string* reason) const
{
  if (!this->is_identical(t, false, true, reason))
    return false;

  // A redeclaration of a function is required to use the same names
  // for the receiver and parameters.
  if (this->receiver() != NULL
      && this->receiver()->name() != t->receiver()->name()
      && this->receiver()->name() != Import::import_marker
      && t->receiver()->name() != Import::import_marker)
    {
      if (reason != NULL)
        *reason = "receiver name changed";
      return false;
    }

  const Typed_identifier_list* parms1 = this->parameters();
  const Typed_identifier_list* parms2 = t->parameters();
  if (parms1 != NULL)
    {
      Typed_identifier_list::const_iterator p1 = parms1->begin();
      for (Typed_identifier_list::const_iterator p2 = parms2->begin();
           p2 != parms2->end();
           ++p2, ++p1)
        {
          if (p1->name() != p2->name()
              && p1->name() != Import::import_marker
              && p2->name() != Import::import_marker)
            {
              if (reason != NULL)
                *reason = "parameter name changed";
              return false;
            }

          // This is called at parse time, so we may have unknown
          // types.
          Type* t1 = p1->type()->forwarded();
          Type* t2 = p2->type()->forwarded();
          if (t1 != t2
              && t1->forward_declaration_type() != NULL
              && (t2->forward_declaration_type() == NULL
                  || (t1->forward_declaration_type()->named_object()
                      != t2->forward_declaration_type()->named_object())))
            return false;
        }
    }

  const Typed_identifier_list* results1 = this->results();
  const Typed_identifier_list* results2 = t->results();
  if (results1 != NULL)
    {
      Typed_identifier_list::const_iterator res1 = results1->begin();
      for (Typed_identifier_list::const_iterator res2 = results2->begin();
           res2 != results2->end();
           ++res2, ++res1)
        {
          if (res1->name() != res2->name()
              && res1->name() != Import::import_marker
              && res2->name() != Import::import_marker)
            {
              if (reason != NULL)
                *reason = "result name changed";
              return false;
            }

          // This is called at parse time, so we may have unknown
          // types.
          Type* t1 = res1->type()->forwarded();
          Type* t2 = res2->type()->forwarded();
          if (t1 != t2
              && t1->forward_declaration_type() != NULL
              && (t2->forward_declaration_type() == NULL
                  || (t1->forward_declaration_type()->named_object()
                      != t2->forward_declaration_type()->named_object())))
            return false;
        }
    }

  return true;
}

// Check whether T is the same as this type.

bool
Function_type::is_identical(const Function_type* t, bool ignore_receiver,
                            bool errors_are_identical,
                            std::string* reason) const
{
  if (!ignore_receiver)
    {
      const Typed_identifier* r1 = this->receiver();
      const Typed_identifier* r2 = t->receiver();
      if ((r1 != NULL) != (r2 != NULL))
        {
          if (reason != NULL)
            *reason = _("different receiver types");
          return false;
        }
      if (r1 != NULL)
        {
          if (!Type::are_identical(r1->type(), r2->type(), errors_are_identical,
                                   reason))
            {
              if (reason != NULL && !reason->empty())
                *reason = "receiver: " + *reason;
              return false;
            }
        }
    }

  const Typed_identifier_list* parms1 = this->parameters();
  const Typed_identifier_list* parms2 = t->parameters();
  if ((parms1 != NULL) != (parms2 != NULL))
    {
      if (reason != NULL)
        *reason = _("different number of parameters");
      return false;
    }
  if (parms1 != NULL)
    {
      Typed_identifier_list::const_iterator p1 = parms1->begin();
      for (Typed_identifier_list::const_iterator p2 = parms2->begin();
           p2 != parms2->end();
           ++p2, ++p1)
        {
          if (p1 == parms1->end())
            {
              if (reason != NULL)
                *reason = _("different number of parameters");
              return false;
            }

          if (!Type::are_identical(p1->type(), p2->type(),
                                   errors_are_identical, NULL))
            {
              if (reason != NULL)
                *reason = _("different parameter types");
              return false;
            }
        }
      if (p1 != parms1->end())
        {
          if (reason != NULL)
            *reason = _("different number of parameters");
        return false;
        }
    }

  if (this->is_varargs() != t->is_varargs())
    {
      if (reason != NULL)
        *reason = _("different varargs");
      return false;
    }

  const Typed_identifier_list* results1 = this->results();
  const Typed_identifier_list* results2 = t->results();
  if ((results1 != NULL) != (results2 != NULL))
    {
      if (reason != NULL)
        *reason = _("different number of results");
      return false;
    }
  if (results1 != NULL)
    {
      Typed_identifier_list::const_iterator res1 = results1->begin();
      for (Typed_identifier_list::const_iterator res2 = results2->begin();
           res2 != results2->end();
           ++res2, ++res1)
        {
          if (res1 == results1->end())
            {
              if (reason != NULL)
                *reason = _("different number of results");
              return false;
            }

          if (!Type::are_identical(res1->type(), res2->type(),
                                   errors_are_identical, NULL))
            {
              if (reason != NULL)
                *reason = _("different result types");
              return false;
            }
        }
      if (res1 != results1->end())
        {
          if (reason != NULL)
            *reason = _("different number of results");
          return false;
        }
    }

  return true;
}

// Hash code.

unsigned int
Function_type::do_hash_for_method(Gogo* gogo) const
{
  unsigned int ret = 0;
  // We ignore the receiver type for hash codes, because we need to
  // get the same hash code for a method in an interface and a method
  // declared for a type.  The former will not have a receiver.
  if (this->parameters_ != NULL)
    {
      int shift = 1;
      for (Typed_identifier_list::const_iterator p = this->parameters_->begin();
           p != this->parameters_->end();
           ++p, ++shift)
        ret += p->type()->hash_for_method(gogo) << shift;
    }
  if (this->results_ != NULL)
    {
      int shift = 2;
      for (Typed_identifier_list::const_iterator p = this->results_->begin();
           p != this->results_->end();
           ++p, ++shift)
        ret += p->type()->hash_for_method(gogo) << shift;
    }
  if (this->is_varargs_)
    ret += 1;
  ret <<= 4;
  return ret;
}

// Get the backend representation for a function type.

Btype*
Function_type::get_function_backend(Gogo* gogo)
{
  Backend::Btyped_identifier breceiver;
  if (this->receiver_ != NULL)
    {
      breceiver.name = Gogo::unpack_hidden_name(this->receiver_->name());

      // We always pass the address of the receiver parameter, in
      // order to make interface calls work with unknown types.
      Type* rtype = this->receiver_->type();
      if (rtype->points_to() == NULL)
        rtype = Type::make_pointer_type(rtype);
      breceiver.btype = rtype->get_backend(gogo);
      breceiver.location = this->receiver_->location();
    }

  std::vector<Backend::Btyped_identifier> bparameters;
  if (this->parameters_ != NULL)
    {
      bparameters.resize(this->parameters_->size());
      size_t i = 0;
      for (Typed_identifier_list::const_iterator p = this->parameters_->begin();
           p != this->parameters_->end();
           ++p, ++i)
        {
          bparameters[i].name = Gogo::unpack_hidden_name(p->name());
          bparameters[i].btype = p->type()->get_backend(gogo);
          bparameters[i].location = p->location();
        }
      go_assert(i == bparameters.size());
    }

  std::vector<Backend::Btyped_identifier> bresults;
  if (this->results_ != NULL)
    {
      bresults.resize(this->results_->size());
      size_t i = 0;
      for (Typed_identifier_list::const_iterator p = this->results_->begin();
           p != this->results_->end();
           ++p, ++i)
        {
          bresults[i].name = Gogo::unpack_hidden_name(p->name());
          bresults[i].btype = p->type()->get_backend(gogo);
          bresults[i].location = p->location();
        }
      go_assert(i == bresults.size());
    }

  return gogo->backend()->function_type(breceiver, bparameters, bresults,
                                        this->location());
}

// A hash table mapping function types to their backend placeholders.

Function_type::Placeholders Function_type::placeholders;

// Get the backend representation for a function type.  If we are
// still converting types, and this types has multiple results, return
// a placeholder instead.  We do this because for multiple results we
// build a struct, and we need to make sure that all the types in the
// struct are valid before we create the struct.

Btype*
Function_type::do_get_backend(Gogo* gogo)
{
  if (!gogo->named_types_are_converted()
      && this->results_ != NULL
      && this->results_->size() > 1)
    {
      Btype* placeholder =
        gogo->backend()->placeholder_pointer_type("", this->location(), true);
      Function_type::placeholders.push_back(std::make_pair(this, placeholder));
      return placeholder;
    }
  return this->get_function_backend(gogo);
}

// Convert function types after all named types are converted.

void
Function_type::convert_types(Gogo* gogo)
{
  for (Placeholders::const_iterator p = Function_type::placeholders.begin();
       p != Function_type::placeholders.end();
       ++p)
    {
      Btype* bt = p->first->get_function_backend(gogo);
      if (!gogo->backend()->set_placeholder_function_type(p->second, bt))
        go_assert(saw_errors());
    }
}

// The type of a function type descriptor.

Type*
Function_type::make_function_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* tdt = Type::make_type_descriptor_type();
      Type* ptdt = Type::make_type_descriptor_ptr_type();

      Type* bool_type = Type::lookup_bool_type();

      Type* slice_type = Type::make_array_type(ptdt, NULL);

      Struct_type* s = Type::make_builtin_struct_type(4,
                                                      "", tdt,
                                                      "dotdotdot", bool_type,
                                                      "in", slice_type,
                                                      "out", slice_type);

      ret = Type::make_builtin_named_type("FuncType", s);
    }

  return ret;
}

// The type descriptor for a function type.

Expression*
Function_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  source_location bloc = BUILTINS_LOCATION;

  Type* ftdt = Function_type::make_function_type_descriptor_type();

  const Struct_field_list* fields = ftdt->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(4);

  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->field_name() == "commonType");
  vals->push_back(this->type_descriptor_constructor(gogo,
                                                    RUNTIME_TYPE_KIND_FUNC,
                                                    name, NULL, true));

  ++p;
  go_assert(p->field_name() == "dotdotdot");
  vals->push_back(Expression::make_boolean(this->is_varargs(), bloc));

  ++p;
  go_assert(p->field_name() == "in");
  vals->push_back(this->type_descriptor_params(p->type(), this->receiver(),
                                               this->parameters()));

  ++p;
  go_assert(p->field_name() == "out");
  vals->push_back(this->type_descriptor_params(p->type(), NULL,
                                               this->results()));

  ++p;
  go_assert(p == fields->end());

  return Expression::make_struct_composite_literal(ftdt, vals, bloc);
}

// Return a composite literal for the parameters or results of a type
// descriptor.

Expression*
Function_type::type_descriptor_params(Type* params_type,
                                      const Typed_identifier* receiver,
                                      const Typed_identifier_list* params)
{
  source_location bloc = BUILTINS_LOCATION;

  if (receiver == NULL && params == NULL)
    return Expression::make_slice_composite_literal(params_type, NULL, bloc);

  Expression_list* vals = new Expression_list();
  vals->reserve((params == NULL ? 0 : params->size())
                + (receiver != NULL ? 1 : 0));

  if (receiver != NULL)
    vals->push_back(Expression::make_type_descriptor(receiver->type(), bloc));

  if (params != NULL)
    {
      for (Typed_identifier_list::const_iterator p = params->begin();
           p != params->end();
           ++p)
        vals->push_back(Expression::make_type_descriptor(p->type(), bloc));
    }

  return Expression::make_slice_composite_literal(params_type, vals, bloc);
}

// The reflection string.

void
Function_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  // FIXME: Turn this off until we straighten out the type of the
  // struct field used in a go statement which calls a method.
  // go_assert(this->receiver_ == NULL);

  ret->append("func");

  if (this->receiver_ != NULL)
    {
      ret->push_back('(');
      this->append_reflection(this->receiver_->type(), gogo, ret);
      ret->push_back(')');
    }

  ret->push_back('(');
  const Typed_identifier_list* params = this->parameters();
  if (params != NULL)
    {
      bool is_varargs = this->is_varargs_;
      for (Typed_identifier_list::const_iterator p = params->begin();
           p != params->end();
           ++p)
        {
          if (p != params->begin())
            ret->append(", ");
          if (!is_varargs || p + 1 != params->end())
            this->append_reflection(p->type(), gogo, ret);
          else
            {
              ret->append("...");
              this->append_reflection(p->type()->array_type()->element_type(),
                                      gogo, ret);
            }
        }
    }
  ret->push_back(')');

  const Typed_identifier_list* results = this->results();
  if (results != NULL && !results->empty())
    {
      if (results->size() == 1)
        ret->push_back(' ');
      else
        ret->append(" (");
      for (Typed_identifier_list::const_iterator p = results->begin();
           p != results->end();
           ++p)
        {
          if (p != results->begin())
            ret->append(", ");
          this->append_reflection(p->type(), gogo, ret);
        }
      if (results->size() > 1)
        ret->push_back(')');
    }
}

// Mangled name.

void
Function_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  ret->push_back('F');

  if (this->receiver_ != NULL)
    {
      ret->push_back('m');
      this->append_mangled_name(this->receiver_->type(), gogo, ret);
    }

  const Typed_identifier_list* params = this->parameters();
  if (params != NULL)
    {
      ret->push_back('p');
      for (Typed_identifier_list::const_iterator p = params->begin();
           p != params->end();
           ++p)
        this->append_mangled_name(p->type(), gogo, ret);
      if (this->is_varargs_)
        ret->push_back('V');
      ret->push_back('e');
    }

  const Typed_identifier_list* results = this->results();
  if (results != NULL)
    {
      ret->push_back('r');
      for (Typed_identifier_list::const_iterator p = results->begin();
           p != results->end();
           ++p)
        this->append_mangled_name(p->type(), gogo, ret);
      ret->push_back('e');
    }

  ret->push_back('e');
}

// Export a function type.

void
Function_type::do_export(Export* exp) const
{
  // We don't write out the receiver.  The only function types which
  // should have a receiver are the ones associated with explicitly
  // defined methods.  For those the receiver type is written out by
  // Function::export_func.

  exp->write_c_string("(");
  bool first = true;
  if (this->parameters_ != NULL)
    {
      bool is_varargs = this->is_varargs_;
      for (Typed_identifier_list::const_iterator p =
             this->parameters_->begin();
           p != this->parameters_->end();
           ++p)
        {
          if (first)
            first = false;
          else
            exp->write_c_string(", ");
          if (!is_varargs || p + 1 != this->parameters_->end())
            exp->write_type(p->type());
          else
            {
              exp->write_c_string("...");
              exp->write_type(p->type()->array_type()->element_type());
            }
        }
    }
  exp->write_c_string(")");

  const Typed_identifier_list* results = this->results_;
  if (results != NULL)
    {
      exp->write_c_string(" ");
      if (results->size() == 1)
        exp->write_type(results->begin()->type());
      else
        {
          first = true;
          exp->write_c_string("(");
          for (Typed_identifier_list::const_iterator p = results->begin();
               p != results->end();
               ++p)
            {
              if (first)
                first = false;
              else
                exp->write_c_string(", ");
              exp->write_type(p->type());
            }
          exp->write_c_string(")");
        }
    }
}

// Import a function type.

Function_type*
Function_type::do_import(Import* imp)
{
  imp->require_c_string("(");
  Typed_identifier_list* parameters;
  bool is_varargs = false;
  if (imp->peek_char() == ')')
    parameters = NULL;
  else
    {
      parameters = new Typed_identifier_list();
      while (true)
        {
          if (imp->match_c_string("..."))
            {
              imp->advance(3);
              is_varargs = true;
            }

          Type* ptype = imp->read_type();
          if (is_varargs)
            ptype = Type::make_array_type(ptype, NULL);
          parameters->push_back(Typed_identifier(Import::import_marker,
                                                 ptype, imp->location()));
          if (imp->peek_char() != ',')
            break;
          go_assert(!is_varargs);
          imp->require_c_string(", ");
        }
    }
  imp->require_c_string(")");

  Typed_identifier_list* results;
  if (imp->peek_char() != ' ')
    results = NULL;
  else
    {
      imp->advance(1);
      results = new Typed_identifier_list;
      if (imp->peek_char() != '(')
        {
          Type* rtype = imp->read_type();
          results->push_back(Typed_identifier(Import::import_marker, rtype,
                                              imp->location()));
        }
      else
        {
          imp->advance(1);
          while (true)
            {
              Type* rtype = imp->read_type();
              results->push_back(Typed_identifier(Import::import_marker,
                                                  rtype, imp->location()));
              if (imp->peek_char() != ',')
                break;
              imp->require_c_string(", ");
            }
          imp->require_c_string(")");
        }
    }

  Function_type* ret = Type::make_function_type(NULL, parameters, results,
                                                imp->location());
  if (is_varargs)
    ret->set_is_varargs();
  return ret;
}

// Make a copy of a function type without a receiver.

Function_type*
Function_type::copy_without_receiver() const
{
  go_assert(this->is_method());
  Function_type *ret = Type::make_function_type(NULL, this->parameters_,
                                                this->results_,
                                                this->location_);
  if (this->is_varargs())
    ret->set_is_varargs();
  if (this->is_builtin())
    ret->set_is_builtin();
  return ret;
}

// Make a copy of a function type with a receiver.

Function_type*
Function_type::copy_with_receiver(Type* receiver_type) const
{
  go_assert(!this->is_method());
  Typed_identifier* receiver = new Typed_identifier("", receiver_type,
                                                    this->location_);
  return Type::make_function_type(receiver, this->parameters_,
                                  this->results_, this->location_);
}

// Make a function type.

Function_type*
Type::make_function_type(Typed_identifier* receiver,
                         Typed_identifier_list* parameters,
                         Typed_identifier_list* results,
                         source_location location)
{
  return new Function_type(receiver, parameters, results, location);
}

// Class Pointer_type.

// Traversal.

int
Pointer_type::do_traverse(Traverse* traverse)
{
  return Type::traverse(this->to_type_, traverse);
}

// Hash code.

unsigned int
Pointer_type::do_hash_for_method(Gogo* gogo) const
{
  return this->to_type_->hash_for_method(gogo) << 4;
}

// The tree for a pointer type.

Btype*
Pointer_type::do_get_backend(Gogo* gogo)
{
  Btype* to_btype = this->to_type_->get_backend(gogo);
  return gogo->backend()->pointer_type(to_btype);
}

// The type of a pointer type descriptor.

Type*
Pointer_type::make_pointer_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* tdt = Type::make_type_descriptor_type();
      Type* ptdt = Type::make_type_descriptor_ptr_type();

      Struct_type* s = Type::make_builtin_struct_type(2,
                                                      "", tdt,
                                                      "elem", ptdt);

      ret = Type::make_builtin_named_type("PtrType", s);
    }

  return ret;
}

// The type descriptor for a pointer type.

Expression*
Pointer_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  if (this->is_unsafe_pointer_type())
    {
      go_assert(name != NULL);
      return this->plain_type_descriptor(gogo,
                                         RUNTIME_TYPE_KIND_UNSAFE_POINTER,
                                         name);
    }
  else
    {
      source_location bloc = BUILTINS_LOCATION;

      const Methods* methods;
      Type* deref = this->points_to();
      if (deref->named_type() != NULL)
        methods = deref->named_type()->methods();
      else if (deref->struct_type() != NULL)
        methods = deref->struct_type()->methods();
      else
        methods = NULL;

      Type* ptr_tdt = Pointer_type::make_pointer_type_descriptor_type();

      const Struct_field_list* fields = ptr_tdt->struct_type()->fields();

      Expression_list* vals = new Expression_list();
      vals->reserve(2);

      Struct_field_list::const_iterator p = fields->begin();
      go_assert(p->field_name() == "commonType");
      vals->push_back(this->type_descriptor_constructor(gogo,
                                                        RUNTIME_TYPE_KIND_PTR,
                                                        name, methods, false));

      ++p;
      go_assert(p->field_name() == "elem");
      vals->push_back(Expression::make_type_descriptor(deref, bloc));

      return Expression::make_struct_composite_literal(ptr_tdt, vals, bloc);
    }
}

// Reflection string.

void
Pointer_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  ret->push_back('*');
  this->append_reflection(this->to_type_, gogo, ret);
}

// Mangled name.

void
Pointer_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  ret->push_back('p');
  this->append_mangled_name(this->to_type_, gogo, ret);
}

// Export.

void
Pointer_type::do_export(Export* exp) const
{
  exp->write_c_string("*");
  if (this->is_unsafe_pointer_type())
    exp->write_c_string("any");
  else
    exp->write_type(this->to_type_);
}

// Import.

Pointer_type*
Pointer_type::do_import(Import* imp)
{
  imp->require_c_string("*");
  if (imp->match_c_string("any"))
    {
      imp->advance(3);
      return Type::make_pointer_type(Type::make_void_type());
    }
  Type* to = imp->read_type();
  return Type::make_pointer_type(to);
}

// Make a pointer type.

Pointer_type*
Type::make_pointer_type(Type* to_type)
{
  typedef Unordered_map(Type*, Pointer_type*) Hashtable;
  static Hashtable pointer_types;
  Hashtable::const_iterator p = pointer_types.find(to_type);
  if (p != pointer_types.end())
    return p->second;
  Pointer_type* ret = new Pointer_type(to_type);
  pointer_types[to_type] = ret;
  return ret;
}

// The nil type.  We use a special type for nil because it is not the
// same as any other type.  In C term nil has type void*, but there is
// no such type in Go.

class Nil_type : public Type
{
 public:
  Nil_type()
    : Type(TYPE_NIL)
  { }

 protected:
  Btype*
  do_get_backend(Gogo* gogo)
  { return gogo->backend()->pointer_type(gogo->backend()->void_type()); }

  Expression*
  do_type_descriptor(Gogo*, Named_type*)
  { go_unreachable(); }

  void
  do_reflection(Gogo*, std::string*) const
  { go_unreachable(); }

  void
  do_mangled_name(Gogo*, std::string* ret) const
  { ret->push_back('n'); }
};

// Make the nil type.

Type*
Type::make_nil_type()
{
  static Nil_type singleton_nil_type;
  return &singleton_nil_type;
}

// The type of a function call which returns multiple values.  This is
// really a struct, but we don't want to confuse a function call which
// returns a struct with a function call which returns multiple
// values.

class Call_multiple_result_type : public Type
{
 public:
  Call_multiple_result_type(Call_expression* call)
    : Type(TYPE_CALL_MULTIPLE_RESULT),
      call_(call)
  { }

 protected:
  bool
  do_has_pointer() const
  {
    go_assert(saw_errors());
    return false;
  }

  Btype*
  do_get_backend(Gogo* gogo)
  {
    go_assert(saw_errors());
    return gogo->backend()->error_type();
  }

  Expression*
  do_type_descriptor(Gogo*, Named_type*)
  {
    go_assert(saw_errors());
    return Expression::make_error(UNKNOWN_LOCATION);
  }

  void
  do_reflection(Gogo*, std::string*) const
  { go_assert(saw_errors()); }

  void
  do_mangled_name(Gogo*, std::string*) const
  { go_assert(saw_errors()); }

 private:
  // The expression being called.
  Call_expression* call_;
};

// Make a call result type.

Type*
Type::make_call_multiple_result_type(Call_expression* call)
{
  return new Call_multiple_result_type(call);
}

// Class Struct_field.

// Get the name of a field.

const std::string&
Struct_field::field_name() const
{
  const std::string& name(this->typed_identifier_.name());
  if (!name.empty())
    return name;
  else
    {
      // This is called during parsing, before anything is lowered, so
      // we have to be pretty careful to avoid dereferencing an
      // unknown type name.
      Type* t = this->typed_identifier_.type();
      Type* dt = t;
      if (t->classification() == Type::TYPE_POINTER)
        {
          // Very ugly.
          Pointer_type* ptype = static_cast<Pointer_type*>(t);
          dt = ptype->points_to();
        }
      if (dt->forward_declaration_type() != NULL)
        return dt->forward_declaration_type()->name();
      else if (dt->named_type() != NULL)
        return dt->named_type()->name();
      else if (t->is_error_type() || dt->is_error_type())
        {
          static const std::string error_string = "*error*";
          return error_string;
        }
      else
        {
          // Avoid crashing in the erroneous case where T is named but
          // DT is not.
          go_assert(t != dt);
          if (t->forward_declaration_type() != NULL)
            return t->forward_declaration_type()->name();
          else if (t->named_type() != NULL)
            return t->named_type()->name();
          else
            go_unreachable();
        }
    }
}

// Class Struct_type.

// Traversal.

int
Struct_type::do_traverse(Traverse* traverse)
{
  Struct_field_list* fields = this->fields_;
  if (fields != NULL)
    {
      for (Struct_field_list::iterator p = fields->begin();
           p != fields->end();
           ++p)
        {
          if (Type::traverse(p->type(), traverse) == TRAVERSE_EXIT)
            return TRAVERSE_EXIT;
        }
    }
  return TRAVERSE_CONTINUE;
}

// Verify that the struct type is complete and valid.

bool
Struct_type::do_verify()
{
  Struct_field_list* fields = this->fields_;
  if (fields == NULL)
    return true;
  bool ret = true;
  for (Struct_field_list::iterator p = fields->begin();
       p != fields->end();
       ++p)
    {
      Type* t = p->type();
      if (t->is_undefined())
        {
          error_at(p->location(), "struct field type is incomplete");
          p->set_type(Type::make_error_type());
          ret = false;
        }
      else if (p->is_anonymous())
        {
          if (t->named_type() != NULL && t->points_to() != NULL)
            {
              error_at(p->location(), "embedded type may not be a pointer");
              p->set_type(Type::make_error_type());
              return false;
            }
          if (t->points_to() != NULL
              && t->points_to()->interface_type() != NULL)
            {
              error_at(p->location(),
                       "embedded type may not be pointer to interface");
              p->set_type(Type::make_error_type());
              return false;
            }
        }
    }
  return ret;
}

// Whether this contains a pointer.

bool
Struct_type::do_has_pointer() const
{
  const Struct_field_list* fields = this->fields();
  if (fields == NULL)
    return false;
  for (Struct_field_list::const_iterator p = fields->begin();
       p != fields->end();
       ++p)
    {
      if (p->type()->has_pointer())
        return true;
    }
  return false;
}

// Whether this type is identical to T.

bool
Struct_type::is_identical(const Struct_type* t,
                          bool errors_are_identical) const
{
  const Struct_field_list* fields1 = this->fields();
  const Struct_field_list* fields2 = t->fields();
  if (fields1 == NULL || fields2 == NULL)
    return fields1 == fields2;
  Struct_field_list::const_iterator pf2 = fields2->begin();
  for (Struct_field_list::const_iterator pf1 = fields1->begin();
       pf1 != fields1->end();
       ++pf1, ++pf2)
    {
      if (pf2 == fields2->end())
        return false;
      if (pf1->field_name() != pf2->field_name())
        return false;
      if (pf1->is_anonymous() != pf2->is_anonymous()
          || !Type::are_identical(pf1->type(), pf2->type(),
                                  errors_are_identical, NULL))
        return false;
      if (!pf1->has_tag())
        {
          if (pf2->has_tag())
            return false;
        }
      else
        {
          if (!pf2->has_tag())
            return false;
          if (pf1->tag() != pf2->tag())
            return false;
        }
    }
  if (pf2 != fields2->end())
    return false;
  return true;
}

// Whether this struct type has any hidden fields.

bool
Struct_type::struct_has_hidden_fields(const Named_type* within,
                                      std::string* reason) const
{
  const Struct_field_list* fields = this->fields();
  if (fields == NULL)
    return false;
  const Package* within_package = (within == NULL
                                   ? NULL
                                   : within->named_object()->package());
  for (Struct_field_list::const_iterator pf = fields->begin();
       pf != fields->end();
       ++pf)
    {
      if (within_package != NULL
          && !pf->is_anonymous()
          && Gogo::is_hidden_name(pf->field_name()))
        {
          if (reason != NULL)
            {
              std::string within_name = within->named_object()->message_name();
              std::string name = Gogo::message_name(pf->field_name());
              size_t bufsize = 200 + within_name.length() + name.length();
              char* buf = new char[bufsize];
              snprintf(buf, bufsize,
                       _("implicit assignment of %s%s%s hidden field %s%s%s"),
                       open_quote, within_name.c_str(), close_quote,
                       open_quote, name.c_str(), close_quote);
              reason->assign(buf);
              delete[] buf;
            }
          return true;
        }

      if (pf->type()->has_hidden_fields(within, reason))
        return true;
    }

  return false;
}

// Hash code.

unsigned int
Struct_type::do_hash_for_method(Gogo* gogo) const
{
  unsigned int ret = 0;
  if (this->fields() != NULL)
    {
      for (Struct_field_list::const_iterator pf = this->fields()->begin();
           pf != this->fields()->end();
           ++pf)
        ret = (ret << 1) + pf->type()->hash_for_method(gogo);
    }
  return ret <<= 2;
}

// Find the local field NAME.

const Struct_field*
Struct_type::find_local_field(const std::string& name,
                              unsigned int *pindex) const
{
  const Struct_field_list* fields = this->fields_;
  if (fields == NULL)
    return NULL;
  unsigned int i = 0;
  for (Struct_field_list::const_iterator pf = fields->begin();
       pf != fields->end();
       ++pf, ++i)
    {
      if (pf->field_name() == name)
        {
          if (pindex != NULL)
            *pindex = i;
          return &*pf;
        }
    }
  return NULL;
}

// Return an expression for field NAME in STRUCT_EXPR, or NULL.

Field_reference_expression*
Struct_type::field_reference(Expression* struct_expr, const std::string& name,
                             source_location location) const
{
  unsigned int depth;
  return this->field_reference_depth(struct_expr, name, location, NULL,
                                     &depth);
}

// Return an expression for a field, along with the depth at which it
// was found.

Field_reference_expression*
Struct_type::field_reference_depth(Expression* struct_expr,
                                   const std::string& name,
                                   source_location location,
                                   Saw_named_type* saw,
                                   unsigned int* depth) const
{
  const Struct_field_list* fields = this->fields_;
  if (fields == NULL)
    return NULL;

  // Look for a field with this name.
  unsigned int i = 0;
  for (Struct_field_list::const_iterator pf = fields->begin();
       pf != fields->end();
       ++pf, ++i)
    {
      if (pf->field_name() == name)
        {
          *depth = 0;
          return Expression::make_field_reference(struct_expr, i, location);
        }
    }

  // Look for an anonymous field which contains a field with this
  // name.
  unsigned int found_depth = 0;
  Field_reference_expression* ret = NULL;
  i = 0;
  for (Struct_field_list::const_iterator pf = fields->begin();
       pf != fields->end();
       ++pf, ++i)
    {
      if (!pf->is_anonymous())
        continue;

      Struct_type* st = pf->type()->deref()->struct_type();
      if (st == NULL)
        continue;

      Saw_named_type* hold_saw = saw;
      Saw_named_type saw_here;
      Named_type* nt = pf->type()->named_type();
      if (nt == NULL)
        nt = pf->type()->deref()->named_type();
      if (nt != NULL)
        {
          Saw_named_type* q;
          for (q = saw; q != NULL; q = q->next)
            {
              if (q->nt == nt)
                {
                  // If this is an error, it will be reported
                  // elsewhere.
                  break;
                }
            }
          if (q != NULL)
            continue;
          saw_here.next = saw;
          saw_here.nt = nt;
          saw = &saw_here;
        }

      // Look for a reference using a NULL struct expression.  If we
      // find one, fill in the struct expression with a reference to
      // this field.
      unsigned int subdepth;
      Field_reference_expression* sub = st->field_reference_depth(NULL, name,
                                                                  location,
                                                                  saw,
                                                                  &subdepth);

      saw = hold_saw;

      if (sub == NULL)
        continue;

      if (ret == NULL || subdepth < found_depth)
        {
          if (ret != NULL)
            delete ret;
          ret = sub;
          found_depth = subdepth;
          Expression* here = Expression::make_field_reference(struct_expr, i,
                                                              location);
          if (pf->type()->points_to() != NULL)
            here = Expression::make_unary(OPERATOR_MULT, here, location);
          while (sub->expr() != NULL)
            {
              sub = sub->expr()->deref()->field_reference_expression();
              go_assert(sub != NULL);
            }
          sub->set_struct_expression(here);
        }
      else if (subdepth > found_depth)
        delete sub;
      else
        {
          // We do not handle ambiguity here--it should be handled by
          // Type::bind_field_or_method.
          delete sub;
          found_depth = 0;
          ret = NULL;
        }
    }

  if (ret != NULL)
    *depth = found_depth + 1;

  return ret;
}

// Return the total number of fields, including embedded fields.

unsigned int
Struct_type::total_field_count() const
{
  if (this->fields_ == NULL)
    return 0;
  unsigned int ret = 0;
  for (Struct_field_list::const_iterator pf = this->fields_->begin();
       pf != this->fields_->end();
       ++pf)
    {
      if (!pf->is_anonymous() || pf->type()->deref()->struct_type() == NULL)
        ++ret;
      else
        ret += pf->type()->struct_type()->total_field_count();
    }
  return ret;
}

// Return whether NAME is an unexported field, for better error reporting.

bool
Struct_type::is_unexported_local_field(Gogo* gogo,
                                       const std::string& name) const
{
  const Struct_field_list* fields = this->fields_;
  if (fields != NULL)
    {
      for (Struct_field_list::const_iterator pf = fields->begin();
           pf != fields->end();
           ++pf)
        {
          const std::string& field_name(pf->field_name());
          if (Gogo::is_hidden_name(field_name)
              && name == Gogo::unpack_hidden_name(field_name)
              && gogo->pack_hidden_name(name, false) != field_name)
            return true;
        }
    }
  return false;
}

// Finalize the methods of an unnamed struct.

void
Struct_type::finalize_methods(Gogo* gogo)
{
  if (this->all_methods_ != NULL)
    return;
  Type::finalize_methods(gogo, this, this->location_, &this->all_methods_);
}

// Return the method NAME, or NULL if there isn't one or if it is
// ambiguous.  Set *IS_AMBIGUOUS if the method exists but is
// ambiguous.

Method*
Struct_type::method_function(const std::string& name, bool* is_ambiguous) const
{
  return Type::method_function(this->all_methods_, name, is_ambiguous);
}

// Convert struct fields to the backend representation.  This is not
// declared in types.h so that types.h doesn't have to #include
// backend.h.

static void
get_backend_struct_fields(Gogo* gogo, const Struct_field_list* fields,
                          std::vector<Backend::Btyped_identifier>* bfields)
{
  bfields->resize(fields->size());
  size_t i = 0;
  for (Struct_field_list::const_iterator p = fields->begin();
       p != fields->end();
       ++p, ++i)
    {
      (*bfields)[i].name = Gogo::unpack_hidden_name(p->field_name());
      (*bfields)[i].btype = p->type()->get_backend(gogo);
      (*bfields)[i].location = p->location();
    }
  go_assert(i == fields->size());
}

// Get the tree for a struct type.

Btype*
Struct_type::do_get_backend(Gogo* gogo)
{
  std::vector<Backend::Btyped_identifier> bfields;
  get_backend_struct_fields(gogo, this->fields_, &bfields);
  return gogo->backend()->struct_type(bfields);
}

// The type of a struct type descriptor.

Type*
Struct_type::make_struct_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* tdt = Type::make_type_descriptor_type();
      Type* ptdt = Type::make_type_descriptor_ptr_type();

      Type* uintptr_type = Type::lookup_integer_type("uintptr");
      Type* string_type = Type::lookup_string_type();
      Type* pointer_string_type = Type::make_pointer_type(string_type);

      Struct_type* sf =
        Type::make_builtin_struct_type(5,
                                       "name", pointer_string_type,
                                       "pkgPath", pointer_string_type,
                                       "typ", ptdt,
                                       "tag", pointer_string_type,
                                       "offset", uintptr_type);
      Type* nsf = Type::make_builtin_named_type("structField", sf);

      Type* slice_type = Type::make_array_type(nsf, NULL);

      Struct_type* s = Type::make_builtin_struct_type(2,
                                                      "", tdt,
                                                      "fields", slice_type);

      ret = Type::make_builtin_named_type("StructType", s);
    }

  return ret;
}

// Build a type descriptor for a struct type.

Expression*
Struct_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  source_location bloc = BUILTINS_LOCATION;

  Type* stdt = Struct_type::make_struct_type_descriptor_type();

  const Struct_field_list* fields = stdt->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(2);

  const Methods* methods = this->methods();
  // A named struct should not have methods--the methods should attach
  // to the named type.
  go_assert(methods == NULL || name == NULL);

  Struct_field_list::const_iterator ps = fields->begin();
  go_assert(ps->field_name() == "commonType");
  vals->push_back(this->type_descriptor_constructor(gogo,
                                                    RUNTIME_TYPE_KIND_STRUCT,
                                                    name, methods, true));

  ++ps;
  go_assert(ps->field_name() == "fields");

  Expression_list* elements = new Expression_list();
  elements->reserve(this->fields_->size());
  Type* element_type = ps->type()->array_type()->element_type();
  for (Struct_field_list::const_iterator pf = this->fields_->begin();
       pf != this->fields_->end();
       ++pf)
    {
      const Struct_field_list* f = element_type->struct_type()->fields();

      Expression_list* fvals = new Expression_list();
      fvals->reserve(5);

      Struct_field_list::const_iterator q = f->begin();
      go_assert(q->field_name() == "name");
      if (pf->is_anonymous())
        fvals->push_back(Expression::make_nil(bloc));
      else
        {
          std::string n = Gogo::unpack_hidden_name(pf->field_name());
          Expression* s = Expression::make_string(n, bloc);
          fvals->push_back(Expression::make_unary(OPERATOR_AND, s, bloc));
        }

      ++q;
      go_assert(q->field_name() == "pkgPath");
      if (!Gogo::is_hidden_name(pf->field_name()))
        fvals->push_back(Expression::make_nil(bloc));
      else
        {
          std::string n = Gogo::hidden_name_prefix(pf->field_name());
          Expression* s = Expression::make_string(n, bloc);
          fvals->push_back(Expression::make_unary(OPERATOR_AND, s, bloc));
        }

      ++q;
      go_assert(q->field_name() == "typ");
      fvals->push_back(Expression::make_type_descriptor(pf->type(), bloc));

      ++q;
      go_assert(q->field_name() == "tag");
      if (!pf->has_tag())
        fvals->push_back(Expression::make_nil(bloc));
      else
        {
          Expression* s = Expression::make_string(pf->tag(), bloc);
          fvals->push_back(Expression::make_unary(OPERATOR_AND, s, bloc));
        }

      ++q;
      go_assert(q->field_name() == "offset");
      fvals->push_back(Expression::make_struct_field_offset(this, &*pf));

      Expression* v = Expression::make_struct_composite_literal(element_type,
                                                                fvals, bloc);
      elements->push_back(v);
    }

  vals->push_back(Expression::make_slice_composite_literal(ps->type(),
                                                           elements, bloc));

  return Expression::make_struct_composite_literal(stdt, vals, bloc);
}

// Reflection string.

void
Struct_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  ret->append("struct { ");

  for (Struct_field_list::const_iterator p = this->fields_->begin();
       p != this->fields_->end();
       ++p)
    {
      if (p != this->fields_->begin())
        ret->append("; ");
      if (p->is_anonymous())
        ret->push_back('?');
      else
        ret->append(Gogo::unpack_hidden_name(p->field_name()));
      ret->push_back(' ');
      this->append_reflection(p->type(), gogo, ret);

      if (p->has_tag())
        {
          const std::string& tag(p->tag());
          ret->append(" \"");
          for (std::string::const_iterator p = tag.begin();
               p != tag.end();
               ++p)
            {
              if (*p == '\0')
                ret->append("\\x00");
              else if (*p == '\n')
                ret->append("\\n");
              else if (*p == '\t')
                ret->append("\\t");
              else if (*p == '"')
                ret->append("\\\"");
              else if (*p == '\\')
                ret->append("\\\\");
              else
                ret->push_back(*p);
            }
          ret->push_back('"');
        }
    }

  ret->append(" }");
}

// Mangled name.

void
Struct_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  ret->push_back('S');

  const Struct_field_list* fields = this->fields_;
  if (fields != NULL)
    {
      for (Struct_field_list::const_iterator p = fields->begin();
           p != fields->end();
           ++p)
        {
          if (p->is_anonymous())
            ret->append("0_");
          else
            {
              std::string n = Gogo::unpack_hidden_name(p->field_name());
              char buf[20];
              snprintf(buf, sizeof buf, "%u_",
                       static_cast<unsigned int>(n.length()));
              ret->append(buf);
              ret->append(n);
            }
          this->append_mangled_name(p->type(), gogo, ret);
          if (p->has_tag())
            {
              const std::string& tag(p->tag());
              std::string out;
              for (std::string::const_iterator p = tag.begin();
                   p != tag.end();
                   ++p)
                {
                  if (ISALNUM(*p) || *p == '_')
                    out.push_back(*p);
                  else
                    {
                      char buf[20];
                      snprintf(buf, sizeof buf, ".%x.",
                               static_cast<unsigned int>(*p));
                      out.append(buf);
                    }
                }
              char buf[20];
              snprintf(buf, sizeof buf, "T%u_",
                       static_cast<unsigned int>(out.length()));
              ret->append(buf);
              ret->append(out);
            }
        }
    }

  ret->push_back('e');
}

// Export.

void
Struct_type::do_export(Export* exp) const
{
  exp->write_c_string("struct { ");
  const Struct_field_list* fields = this->fields_;
  go_assert(fields != NULL);
  for (Struct_field_list::const_iterator p = fields->begin();
       p != fields->end();
       ++p)
    {
      if (p->is_anonymous())
        exp->write_string("? ");
      else
        {
          exp->write_string(p->field_name());
          exp->write_c_string(" ");
        }
      exp->write_type(p->type());

      if (p->has_tag())
        {
          exp->write_c_string(" ");
          Expression* expr = Expression::make_string(p->tag(),
                                                     BUILTINS_LOCATION);
          expr->export_expression(exp);
          delete expr;
        }

      exp->write_c_string("; ");
    }
  exp->write_c_string("}");
}

// Import.

Struct_type*
Struct_type::do_import(Import* imp)
{
  imp->require_c_string("struct { ");
  Struct_field_list* fields = new Struct_field_list;
  if (imp->peek_char() != '}')
    {
      while (true)
        {
          std::string name;
          if (imp->match_c_string("? "))
            imp->advance(2);
          else
            {
              name = imp->read_identifier();
              imp->require_c_string(" ");
            }
          Type* ftype = imp->read_type();

          Struct_field sf(Typed_identifier(name, ftype, imp->location()));

          if (imp->peek_char() == ' ')
            {
              imp->advance(1);
              Expression* expr = Expression::import_expression(imp);
              String_expression* sexpr = expr->string_expression();
              go_assert(sexpr != NULL);
              sf.set_tag(sexpr->val());
              delete sexpr;
            }

          imp->require_c_string("; ");
          fields->push_back(sf);
          if (imp->peek_char() == '}')
            break;
        }
    }
  imp->require_c_string("}");

  return Type::make_struct_type(fields, imp->location());
}

// Make a struct type.

Struct_type*
Type::make_struct_type(Struct_field_list* fields,
                       source_location location)
{
  return new Struct_type(fields, location);
}

// Class Array_type.

// Whether two array types are identical.

bool
Array_type::is_identical(const Array_type* t, bool errors_are_identical) const
{
  if (!Type::are_identical(this->element_type(), t->element_type(),
                           errors_are_identical, NULL))
    return false;

  Expression* l1 = this->length();
  Expression* l2 = t->length();

  // Slices of the same element type are identical.
  if (l1 == NULL && l2 == NULL)
    return true;

  // Arrays of the same element type are identical if they have the
  // same length.
  if (l1 != NULL && l2 != NULL)
    {
      if (l1 == l2)
        return true;

      // Try to determine the lengths.  If we can't, assume the arrays
      // are not identical.
      bool ret = false;
      mpz_t v1;
      mpz_init(v1);
      Type* type1;
      mpz_t v2;
      mpz_init(v2);
      Type* type2;
      if (l1->integer_constant_value(true, v1, &type1)
          && l2->integer_constant_value(true, v2, &type2))
        ret = mpz_cmp(v1, v2) == 0;
      mpz_clear(v1);
      mpz_clear(v2);
      return ret;
    }

  // Otherwise the arrays are not identical.
  return false;
}

// Traversal.

int
Array_type::do_traverse(Traverse* traverse)
{
  if (Type::traverse(this->element_type_, traverse) == TRAVERSE_EXIT)
    return TRAVERSE_EXIT;
  if (this->length_ != NULL
      && Expression::traverse(&this->length_, traverse) == TRAVERSE_EXIT)
    return TRAVERSE_EXIT;
  return TRAVERSE_CONTINUE;
}

// Check that the length is valid.

bool
Array_type::verify_length()
{
  if (this->length_ == NULL)
    return true;

  Type_context context(Type::lookup_integer_type("int"), false);
  this->length_->determine_type(&context);

  if (!this->length_->is_constant())
    {
      error_at(this->length_->location(), "array bound is not constant");
      return false;
    }

  mpz_t val;
  mpz_init(val);
  Type* vt;
  if (!this->length_->integer_constant_value(true, val, &vt))
    {
      mpfr_t fval;
      mpfr_init(fval);
      if (!this->length_->float_constant_value(fval, &vt))
        {
          if (this->length_->type()->integer_type() != NULL
              || this->length_->type()->float_type() != NULL)
            error_at(this->length_->location(),
                     "array bound is not constant");
          else
            error_at(this->length_->location(),
                     "array bound is not numeric");
          mpfr_clear(fval);
          mpz_clear(val);
          return false;
        }
      if (!mpfr_integer_p(fval))
        {
          error_at(this->length_->location(),
                   "array bound truncated to integer");
          mpfr_clear(fval);
          mpz_clear(val);
          return false;
        }
      mpz_init(val);
      mpfr_get_z(val, fval, GMP_RNDN);
      mpfr_clear(fval);
    }

  if (mpz_sgn(val) < 0)
    {
      error_at(this->length_->location(), "negative array bound");
      mpz_clear(val);
      return false;
    }

  Type* int_type = Type::lookup_integer_type("int");
  int tbits = int_type->integer_type()->bits();
  int vbits = mpz_sizeinbase(val, 2);
  if (vbits + 1 > tbits)
    {
      error_at(this->length_->location(), "array bound overflows");
      mpz_clear(val);
      return false;
    }

  mpz_clear(val);

  return true;
}

// Verify the type.

bool
Array_type::do_verify()
{
  if (!this->verify_length())
    {
      this->length_ = Expression::make_error(this->length_->location());
      return false;
    }
  return true;
}

// Array type hash code.

unsigned int
Array_type::do_hash_for_method(Gogo* gogo) const
{
  // There is no very convenient way to get a hash code for the
  // length.
  return this->element_type_->hash_for_method(gogo) + 1;
}

// See if the expression passed to make is suitable.  The first
// argument is required, and gives the length.  An optional second
// argument is permitted for the capacity.

bool
Array_type::do_check_make_expression(Expression_list* args,
                                     source_location location)
{
  go_assert(this->length_ == NULL);
  if (args == NULL || args->empty())
    {
      error_at(location, "length required when allocating a slice");
      return false;
    }
  else if (args->size() > 2)
    {
      error_at(location, "too many expressions passed to make");
      return false;
    }
  else
    {
      if (!Type::check_int_value(args->front(),
                                 _("bad length when making slice"), location))
        return false;

      if (args->size() > 1)
        {
          if (!Type::check_int_value(args->back(),
                                     _("bad capacity when making slice"),
                                     location))
            return false;
        }

      return true;
    }
}

// Get a tree for the length of a fixed array.  The length may be
// computed using a function call, so we must only evaluate it once.

tree
Array_type::get_length_tree(Gogo* gogo)
{
  go_assert(this->length_ != NULL);
  if (this->length_tree_ == NULL_TREE)
    {
      mpz_t val;
      mpz_init(val);
      Type* t;
      if (this->length_->integer_constant_value(true, val, &t))
        {
          if (t == NULL)
            t = Type::lookup_integer_type("int");
          else if (t->is_abstract())
            t = t->make_non_abstract_type();
          tree tt = type_to_tree(t->get_backend(gogo));
          this->length_tree_ = Expression::integer_constant_tree(val, tt);
          mpz_clear(val);
        }
      else
        {
          mpz_clear(val);

          // Make up a translation context for the array length
          // expression.  FIXME: This won't work in general.
          Translate_context context(gogo, NULL, NULL, NULL);
          tree len = this->length_->get_tree(&context);
          if (len != error_mark_node)
            {
              len = convert_to_integer(integer_type_node, len);
              len = save_expr(len);
            }
          this->length_tree_ = len;
        }
    }
  return this->length_tree_;
}

// Get the backend representation of the fields of a slice.  This is
// not declared in types.h so that types.h doesn't have to #include
// backend.h.
//
// We use int for the count and capacity fields.  This matches 6g.
// The language more or less assumes that we can't allocate space of a
// size which does not fit in int.

static void
get_backend_slice_fields(Gogo* gogo, Array_type* type,
                         std::vector<Backend::Btyped_identifier>* bfields)
{
  bfields->resize(3);

  Type* pet = Type::make_pointer_type(type->element_type());
  Btype* pbet = pet->get_backend(gogo);

  Backend::Btyped_identifier* p = &(*bfields)[0];
  p->name = "__values";
  p->btype = pbet;
  p->location = UNKNOWN_LOCATION;

  Type* int_type = Type::lookup_integer_type("int");

  p = &(*bfields)[1];
  p->name = "__count";
  p->btype = int_type->get_backend(gogo);
  p->location = UNKNOWN_LOCATION;

  p = &(*bfields)[2];
  p->name = "__capacity";
  p->btype = int_type->get_backend(gogo);
  p->location = UNKNOWN_LOCATION;
}

// Get a tree for the type of this array.  A fixed array is simply
// represented as ARRAY_TYPE with the appropriate index--i.e., it is
// just like an array in C.  An open array is a struct with three
// fields: a data pointer, the length, and the capacity.

Btype*
Array_type::do_get_backend(Gogo* gogo)
{
  if (this->length_ == NULL)
    {
      std::vector<Backend::Btyped_identifier> bfields;
      get_backend_slice_fields(gogo, this, &bfields);
      return gogo->backend()->struct_type(bfields);
    }
  else
    {
      Btype* element = this->get_backend_element(gogo);
      Bexpression* len = this->get_backend_length(gogo);
      return gogo->backend()->array_type(element, len);
    }
}

// Return the backend representation of the element type.
Btype*
Array_type::get_backend_element(Gogo* gogo)
{
  return this->element_type_->get_backend(gogo);
}

// Return the backend representation of the length.

Bexpression*
Array_type::get_backend_length(Gogo* gogo)
{
  return tree_to_expr(this->get_length_tree(gogo));
}

// Handle the builtin make function for a slice.

tree
Array_type::do_make_expression_tree(Translate_context* context,
                                    Expression_list* args,
                                    source_location location)
{
  go_assert(this->length_ == NULL);

  Gogo* gogo = context->gogo();
  tree type_tree = type_to_tree(this->get_backend(gogo));
  if (type_tree == error_mark_node)
    return error_mark_node;

  tree values_field = TYPE_FIELDS(type_tree);
  go_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(values_field)),
                    "__values") == 0);

  tree count_field = DECL_CHAIN(values_field);
  go_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(count_field)),
                    "__count") == 0);

  tree element_type_tree = type_to_tree(this->element_type_->get_backend(gogo));
  if (element_type_tree == error_mark_node)
    return error_mark_node;
  tree element_size_tree = TYPE_SIZE_UNIT(element_type_tree);

  // The first argument is the number of elements, the optional second
  // argument is the capacity.
  go_assert(args != NULL && args->size() >= 1 && args->size() <= 2);

  tree length_tree = args->front()->get_tree(context);
  if (length_tree == error_mark_node)
    return error_mark_node;
  if (!DECL_P(length_tree))
    length_tree = save_expr(length_tree);
  if (!INTEGRAL_TYPE_P(TREE_TYPE(length_tree)))
    length_tree = convert_to_integer(TREE_TYPE(count_field), length_tree);

  tree bad_index = Expression::check_bounds(length_tree,
                                            TREE_TYPE(count_field),
                                            NULL_TREE, location);

  length_tree = fold_convert_loc(location, TREE_TYPE(count_field), length_tree);
  tree capacity_tree;
  if (args->size() == 1)
    capacity_tree = length_tree;
  else
    {
      capacity_tree = args->back()->get_tree(context);
      if (capacity_tree == error_mark_node)
        return error_mark_node;
      if (!DECL_P(capacity_tree))
        capacity_tree = save_expr(capacity_tree);
      if (!INTEGRAL_TYPE_P(TREE_TYPE(capacity_tree)))
        capacity_tree = convert_to_integer(TREE_TYPE(count_field),
                                           capacity_tree);

      bad_index = Expression::check_bounds(capacity_tree,
                                           TREE_TYPE(count_field),
                                           bad_index, location);

      tree chktype = (((TYPE_SIZE(TREE_TYPE(capacity_tree))
                        > TYPE_SIZE(TREE_TYPE(length_tree)))
                       || ((TYPE_SIZE(TREE_TYPE(capacity_tree))
                            == TYPE_SIZE(TREE_TYPE(length_tree)))
                           && TYPE_UNSIGNED(TREE_TYPE(capacity_tree))))
                      ? TREE_TYPE(capacity_tree)
                      : TREE_TYPE(length_tree));
      tree chk = fold_build2_loc(location, LT_EXPR, boolean_type_node,
                                 fold_convert_loc(location, chktype,
                                                  capacity_tree),
                                 fold_convert_loc(location, chktype,
                                                  length_tree));
      if (bad_index == NULL_TREE)
        bad_index = chk;
      else
        bad_index = fold_build2_loc(location, TRUTH_OR_EXPR, boolean_type_node,
                                    bad_index, chk);

      capacity_tree = fold_convert_loc(location, TREE_TYPE(count_field),
                                       capacity_tree);
    }

  tree size_tree = fold_build2_loc(location, MULT_EXPR, sizetype,
                                   element_size_tree,
                                   fold_convert_loc(location, sizetype,
                                                    capacity_tree));

  tree chk = fold_build2_loc(location, TRUTH_AND_EXPR, boolean_type_node,
                             fold_build2_loc(location, GT_EXPR,
                                             boolean_type_node,
                                             fold_convert_loc(location,
                                                              sizetype,
                                                              capacity_tree),
                                             size_zero_node),
                             fold_build2_loc(location, LT_EXPR,
                                             boolean_type_node,
                                             size_tree, element_size_tree));
  if (bad_index == NULL_TREE)
    bad_index = chk;
  else
    bad_index = fold_build2_loc(location, TRUTH_OR_EXPR, boolean_type_node,
                                bad_index, chk);

  tree space = context->gogo()->allocate_memory(this->element_type_,
                                                size_tree, location);

  space = fold_convert(TREE_TYPE(values_field), space);

  if (bad_index != NULL_TREE && bad_index != boolean_false_node)
    {
      tree crash = Gogo::runtime_error(RUNTIME_ERROR_MAKE_SLICE_OUT_OF_BOUNDS,
                                       location);
      space = build2(COMPOUND_EXPR, TREE_TYPE(space),
                     build3(COND_EXPR, void_type_node,
                            bad_index, crash, NULL_TREE),
                     space);
    }

  return gogo->slice_constructor(type_tree, space, length_tree, capacity_tree);
}

// Return a tree for a pointer to the values in ARRAY.

tree
Array_type::value_pointer_tree(Gogo*, tree array) const
{
  tree ret;
  if (this->length() != NULL)
    {
      // Fixed array.
      ret = fold_convert(build_pointer_type(TREE_TYPE(TREE_TYPE(array))),
                         build_fold_addr_expr(array));
    }
  else
    {
      // Open array.
      tree field = TYPE_FIELDS(TREE_TYPE(array));
      go_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)),
                        "__values") == 0);
      ret = fold_build3(COMPONENT_REF, TREE_TYPE(field), array, field,
                        NULL_TREE);
    }
  if (TREE_CONSTANT(array))
    TREE_CONSTANT(ret) = 1;
  return ret;
}

// Return a tree for the length of the array ARRAY which has this
// type.

tree
Array_type::length_tree(Gogo* gogo, tree array)
{
  if (this->length_ != NULL)
    {
      if (TREE_CODE(array) == SAVE_EXPR)
        return fold_convert(integer_type_node, this->get_length_tree(gogo));
      else
        return omit_one_operand(integer_type_node,
                                this->get_length_tree(gogo), array);
    }

  // This is an open array.  We need to read the length field.

  tree type = TREE_TYPE(array);
  go_assert(TREE_CODE(type) == RECORD_TYPE);

  tree field = DECL_CHAIN(TYPE_FIELDS(type));
  go_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__count") == 0);

  tree ret = build3(COMPONENT_REF, TREE_TYPE(field), array, field, NULL_TREE);
  if (TREE_CONSTANT(array))
    TREE_CONSTANT(ret) = 1;
  return ret;
}

// Return a tree for the capacity of the array ARRAY which has this
// type.

tree
Array_type::capacity_tree(Gogo* gogo, tree array)
{
  if (this->length_ != NULL)
    return omit_one_operand(sizetype, this->get_length_tree(gogo), array);

  // This is an open array.  We need to read the capacity field.

  tree type = TREE_TYPE(array);
  go_assert(TREE_CODE(type) == RECORD_TYPE);

  tree field = DECL_CHAIN(DECL_CHAIN(TYPE_FIELDS(type)));
  go_assert(strcmp(IDENTIFIER_POINTER(DECL_NAME(field)), "__capacity") == 0);

  return build3(COMPONENT_REF, TREE_TYPE(field), array, field, NULL_TREE);
}

// Export.

void
Array_type::do_export(Export* exp) const
{
  exp->write_c_string("[");
  if (this->length_ != NULL)
    this->length_->export_expression(exp);
  exp->write_c_string("] ");
  exp->write_type(this->element_type_);
}

// Import.

Array_type*
Array_type::do_import(Import* imp)
{
  imp->require_c_string("[");
  Expression* length;
  if (imp->peek_char() == ']')
    length = NULL;
  else
    length = Expression::import_expression(imp);
  imp->require_c_string("] ");
  Type* element_type = imp->read_type();
  return Type::make_array_type(element_type, length);
}

// The type of an array type descriptor.

Type*
Array_type::make_array_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* tdt = Type::make_type_descriptor_type();
      Type* ptdt = Type::make_type_descriptor_ptr_type();

      Type* uintptr_type = Type::lookup_integer_type("uintptr");

      Struct_type* sf =
        Type::make_builtin_struct_type(4,
                                       "", tdt,
                                       "elem", ptdt,
                                       "slice", ptdt,
                                       "len", uintptr_type);

      ret = Type::make_builtin_named_type("ArrayType", sf);
    }

  return ret;
}

// The type of an slice type descriptor.

Type*
Array_type::make_slice_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* tdt = Type::make_type_descriptor_type();
      Type* ptdt = Type::make_type_descriptor_ptr_type();

      Struct_type* sf =
        Type::make_builtin_struct_type(2,
                                       "", tdt,
                                       "elem", ptdt);

      ret = Type::make_builtin_named_type("SliceType", sf);
    }

  return ret;
}

// Build a type descriptor for an array/slice type.

Expression*
Array_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  if (this->length_ != NULL)
    return this->array_type_descriptor(gogo, name);
  else
    return this->slice_type_descriptor(gogo, name);
}

// Build a type descriptor for an array type.

Expression*
Array_type::array_type_descriptor(Gogo* gogo, Named_type* name)
{
  source_location bloc = BUILTINS_LOCATION;

  Type* atdt = Array_type::make_array_type_descriptor_type();

  const Struct_field_list* fields = atdt->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(3);

  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->field_name() == "commonType");
  vals->push_back(this->type_descriptor_constructor(gogo,
                                                    RUNTIME_TYPE_KIND_ARRAY,
                                                    name, NULL, true));

  ++p;
  go_assert(p->field_name() == "elem");
  vals->push_back(Expression::make_type_descriptor(this->element_type_, bloc));

  ++p;
  go_assert(p->field_name() == "slice");
  Type* slice_type = Type::make_array_type(this->element_type_, NULL);
  vals->push_back(Expression::make_type_descriptor(slice_type, bloc));

  ++p;
  go_assert(p->field_name() == "len");
  vals->push_back(Expression::make_cast(p->type(), this->length_, bloc));

  ++p;
  go_assert(p == fields->end());

  return Expression::make_struct_composite_literal(atdt, vals, bloc);
}

// Build a type descriptor for a slice type.

Expression*
Array_type::slice_type_descriptor(Gogo* gogo, Named_type* name)
{
  source_location bloc = BUILTINS_LOCATION;

  Type* stdt = Array_type::make_slice_type_descriptor_type();

  const Struct_field_list* fields = stdt->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(2);

  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->field_name() == "commonType");
  vals->push_back(this->type_descriptor_constructor(gogo,
                                                    RUNTIME_TYPE_KIND_SLICE,
                                                    name, NULL, true));

  ++p;
  go_assert(p->field_name() == "elem");
  vals->push_back(Expression::make_type_descriptor(this->element_type_, bloc));

  ++p;
  go_assert(p == fields->end());

  return Expression::make_struct_composite_literal(stdt, vals, bloc);
}

// Reflection string.

void
Array_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  ret->push_back('[');
  if (this->length_ != NULL)
    {
      mpz_t val;
      mpz_init(val);
      Type* type;
      if (!this->length_->integer_constant_value(true, val, &type))
        error_at(this->length_->location(),
                 "array length must be integer constant expression");
      else if (mpz_cmp_si(val, 0) < 0)
        error_at(this->length_->location(), "array length is negative");
      else if (mpz_cmp_ui(val, mpz_get_ui(val)) != 0)
        error_at(this->length_->location(), "array length is too large");
      else
        {
          char buf[50];
          snprintf(buf, sizeof buf, "%lu", mpz_get_ui(val));
          ret->append(buf);
        }
      mpz_clear(val);
    }
  ret->push_back(']');

  this->append_reflection(this->element_type_, gogo, ret);
}

// Mangled name.

void
Array_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  ret->push_back('A');
  this->append_mangled_name(this->element_type_, gogo, ret);
  if (this->length_ != NULL)
    {
      mpz_t val;
      mpz_init(val);
      Type* type;
      if (!this->length_->integer_constant_value(true, val, &type))
        error_at(this->length_->location(),
                 "array length must be integer constant expression");
      else if (mpz_cmp_si(val, 0) < 0)
        error_at(this->length_->location(), "array length is negative");
      else if (mpz_cmp_ui(val, mpz_get_ui(val)) != 0)
        error_at(this->length_->location(), "array size is too large");
      else
        {
          char buf[50];
          snprintf(buf, sizeof buf, "%lu", mpz_get_ui(val));
          ret->append(buf);
        }
      mpz_clear(val);
    }
  ret->push_back('e');
}

// Make an array type.

Array_type*
Type::make_array_type(Type* element_type, Expression* length)
{
  return new Array_type(element_type, length);
}

// Class Map_type.

// Traversal.

int
Map_type::do_traverse(Traverse* traverse)
{
  if (Type::traverse(this->key_type_, traverse) == TRAVERSE_EXIT
      || Type::traverse(this->val_type_, traverse) == TRAVERSE_EXIT)
    return TRAVERSE_EXIT;
  return TRAVERSE_CONTINUE;
}

// Check that the map type is OK.

bool
Map_type::do_verify()
{
  if (this->key_type_->struct_type() != NULL
      || this->key_type_->array_type() != NULL)
    {
      error_at(this->location_, "invalid map key type");
      return false;
    }
  return true;
}

// Whether two map types are identical.

bool
Map_type::is_identical(const Map_type* t, bool errors_are_identical) const
{
  return (Type::are_identical(this->key_type(), t->key_type(),
                              errors_are_identical, NULL)
          && Type::are_identical(this->val_type(), t->val_type(),
                                 errors_are_identical, NULL));
}

// Hash code.

unsigned int
Map_type::do_hash_for_method(Gogo* gogo) const
{
  return (this->key_type_->hash_for_method(gogo)
          + this->val_type_->hash_for_method(gogo)
          + 2);
}

// Check that a call to the builtin make function is valid.  For a map
// the optional argument is the number of spaces to preallocate for
// values.

bool
Map_type::do_check_make_expression(Expression_list* args,
                                   source_location location)
{
  if (args != NULL && !args->empty())
    {
      if (!Type::check_int_value(args->front(), _("bad size when making map"),
                                 location))
        return false;
      else if (args->size() > 1)
        {
          error_at(location, "too many arguments when making map");
          return false;
        }
    }
  return true;
}

// Get the backend representation for a map type.  A map type is
// represented as a pointer to a struct.  The struct is __go_map in
// libgo/map.h.

Btype*
Map_type::do_get_backend(Gogo* gogo)
{
  static Btype* backend_map_type;
  if (backend_map_type == NULL)
    {
      std::vector<Backend::Btyped_identifier> bfields(4);

      Type* pdt = Type::make_type_descriptor_ptr_type();
      bfields[0].name = "__descriptor";
      bfields[0].btype = pdt->get_backend(gogo);
      bfields[0].location = BUILTINS_LOCATION;

      Type* uintptr_type = Type::lookup_integer_type("uintptr");
      bfields[1].name = "__element_count";
      bfields[1].btype = uintptr_type->get_backend(gogo);
      bfields[1].location = BUILTINS_LOCATION;

      bfields[2].name = "__bucket_count";
      bfields[2].btype = bfields[1].btype;
      bfields[2].location = BUILTINS_LOCATION;

      Btype* bvt = gogo->backend()->void_type();
      Btype* bpvt = gogo->backend()->pointer_type(bvt);
      Btype* bppvt = gogo->backend()->pointer_type(bpvt);
      bfields[3].name = "__buckets";
      bfields[3].btype = bppvt;
      bfields[3].location = BUILTINS_LOCATION;

      Btype *bt = gogo->backend()->struct_type(bfields);
      bt = gogo->backend()->named_type("__go_map", bt, BUILTINS_LOCATION);
      backend_map_type = gogo->backend()->pointer_type(bt);
    }
  return backend_map_type;
}

// Return an expression for a newly allocated map.

tree
Map_type::do_make_expression_tree(Translate_context* context,
                                  Expression_list* args,
                                  source_location location)
{
  tree bad_index = NULL_TREE;

  tree expr_tree;
  if (args == NULL || args->empty())
    expr_tree = size_zero_node;
  else
    {
      expr_tree = args->front()->get_tree(context);
      if (expr_tree == error_mark_node)
        return error_mark_node;
      if (!DECL_P(expr_tree))
        expr_tree = save_expr(expr_tree);
      if (!INTEGRAL_TYPE_P(TREE_TYPE(expr_tree)))
        expr_tree = convert_to_integer(sizetype, expr_tree);
      bad_index = Expression::check_bounds(expr_tree, sizetype, bad_index,
                                           location);
    }

  Gogo* gogo = context->gogo();
  tree map_type = type_to_tree(this->get_backend(gogo));

  static tree new_map_fndecl;
  tree ret = Gogo::call_builtin(&new_map_fndecl,
                                location,
                                "__go_new_map",
                                2,
                                map_type,
                                TREE_TYPE(TYPE_FIELDS(TREE_TYPE(map_type))),
                                this->map_descriptor_pointer(gogo, location),
                                sizetype,
                                expr_tree);
  if (ret == error_mark_node)
    return error_mark_node;
  // This can panic if the capacity is out of range.
  TREE_NOTHROW(new_map_fndecl) = 0;

  if (bad_index == NULL_TREE)
    return ret;
  else
    {
      tree crash = Gogo::runtime_error(RUNTIME_ERROR_MAKE_MAP_OUT_OF_BOUNDS,
                                       location);
      return build2(COMPOUND_EXPR, TREE_TYPE(ret),
                    build3(COND_EXPR, void_type_node,
                           bad_index, crash, NULL_TREE),
                    ret);
    }
}

// The type of a map type descriptor.

Type*
Map_type::make_map_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* tdt = Type::make_type_descriptor_type();
      Type* ptdt = Type::make_type_descriptor_ptr_type();

      Struct_type* sf =
        Type::make_builtin_struct_type(3,
                                       "", tdt,
                                       "key", ptdt,
                                       "elem", ptdt);

      ret = Type::make_builtin_named_type("MapType", sf);
    }

  return ret;
}

// Build a type descriptor for a map type.

Expression*
Map_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  source_location bloc = BUILTINS_LOCATION;

  Type* mtdt = Map_type::make_map_type_descriptor_type();

  const Struct_field_list* fields = mtdt->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(3);

  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->field_name() == "commonType");
  vals->push_back(this->type_descriptor_constructor(gogo,
                                                    RUNTIME_TYPE_KIND_MAP,
                                                    name, NULL, true));

  ++p;
  go_assert(p->field_name() == "key");
  vals->push_back(Expression::make_type_descriptor(this->key_type_, bloc));

  ++p;
  go_assert(p->field_name() == "elem");
  vals->push_back(Expression::make_type_descriptor(this->val_type_, bloc));

  ++p;
  go_assert(p == fields->end());

  return Expression::make_struct_composite_literal(mtdt, vals, bloc);
}

// A mapping from map types to map descriptors.

Map_type::Map_descriptors Map_type::map_descriptors;

// Build a map descriptor for this type.  Return a pointer to it.

tree
Map_type::map_descriptor_pointer(Gogo* gogo, source_location location)
{
  Bvariable* bvar = this->map_descriptor(gogo);
  tree var_tree = var_to_tree(bvar);
  if (var_tree == error_mark_node)
    return error_mark_node;
  return build_fold_addr_expr_loc(location, var_tree);
}

// Build a map descriptor for this type.

Bvariable*
Map_type::map_descriptor(Gogo* gogo)
{
  std::pair<Map_type*, Bvariable*> val(this, NULL);
  std::pair<Map_type::Map_descriptors::iterator, bool> ins =
    Map_type::map_descriptors.insert(val);
  if (!ins.second)
    return ins.first->second;

  Type* key_type = this->key_type_;
  Type* val_type = this->val_type_;

  // The map entry type is a struct with three fields.  Build that
  // struct so that we can get the offsets of the key and value within
  // a map entry.  The first field should technically be a pointer to
  // this type itself, but since we only care about field offsets we
  // just use pointer to bool.
  Type* pbool = Type::make_pointer_type(Type::make_boolean_type());
  Struct_type* map_entry_type =
    Type::make_builtin_struct_type(3,
                                   "__next", pbool,
                                   "__key", key_type,
                                   "__val", val_type);

  Type* map_descriptor_type = Map_type::make_map_descriptor_type();

  const Struct_field_list* fields =
    map_descriptor_type->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(4);

  source_location bloc = BUILTINS_LOCATION;

  Struct_field_list::const_iterator p = fields->begin();

  go_assert(p->field_name() == "__map_descriptor");
  vals->push_back(Expression::make_type_descriptor(this, bloc));

  ++p;
  go_assert(p->field_name() == "__entry_size");
  Expression::Type_info type_info = Expression::TYPE_INFO_SIZE;
  vals->push_back(Expression::make_type_info(map_entry_type, type_info));

  Struct_field_list::const_iterator pf = map_entry_type->fields()->begin();
  ++pf;
  go_assert(pf->field_name() == "__key");

  ++p;
  go_assert(p->field_name() == "__key_offset");
  vals->push_back(Expression::make_struct_field_offset(map_entry_type, &*pf));

  ++pf;
  go_assert(pf->field_name() == "__val");

  ++p;
  go_assert(p->field_name() == "__val_offset");
  vals->push_back(Expression::make_struct_field_offset(map_entry_type, &*pf));

  ++p;
  go_assert(p == fields->end());

  Expression* initializer =
    Expression::make_struct_composite_literal(map_descriptor_type, vals, bloc);

  std::string mangled_name = "__go_map_" + this->mangled_name(gogo);
  Btype* map_descriptor_btype = map_descriptor_type->get_backend(gogo);
  Bvariable* bvar = gogo->backend()->immutable_struct(mangled_name, true,
                                                      map_descriptor_btype,
                                                      bloc);

  Translate_context context(gogo, NULL, NULL, NULL);
  context.set_is_const();
  Bexpression* binitializer = tree_to_expr(initializer->get_tree(&context));

  gogo->backend()->immutable_struct_set_init(bvar, mangled_name, true,
                                             map_descriptor_btype, bloc,
                                             binitializer);

  ins.first->second = bvar;
  return bvar;
}

// Build the type of a map descriptor.  This must match the struct
// __go_map_descriptor in libgo/runtime/map.h.

Type*
Map_type::make_map_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* ptdt = Type::make_type_descriptor_ptr_type();
      Type* uintptr_type = Type::lookup_integer_type("uintptr");
      Struct_type* sf =
        Type::make_builtin_struct_type(4,
                                       "__map_descriptor", ptdt,
                                       "__entry_size", uintptr_type,
                                       "__key_offset", uintptr_type,
                                       "__val_offset", uintptr_type);
      ret = Type::make_builtin_named_type("__go_map_descriptor", sf);
    }
  return ret;
}

// Reflection string for a map.

void
Map_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  ret->append("map[");
  this->append_reflection(this->key_type_, gogo, ret);
  ret->append("] ");
  this->append_reflection(this->val_type_, gogo, ret);
}

// Mangled name for a map.

void
Map_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  ret->push_back('M');
  this->append_mangled_name(this->key_type_, gogo, ret);
  ret->append("__");
  this->append_mangled_name(this->val_type_, gogo, ret);
}

// Export a map type.

void
Map_type::do_export(Export* exp) const
{
  exp->write_c_string("map [");
  exp->write_type(this->key_type_);
  exp->write_c_string("] ");
  exp->write_type(this->val_type_);
}

// Import a map type.

Map_type*
Map_type::do_import(Import* imp)
{
  imp->require_c_string("map [");
  Type* key_type = imp->read_type();
  imp->require_c_string("] ");
  Type* val_type = imp->read_type();
  return Type::make_map_type(key_type, val_type, imp->location());
}

// Make a map type.

Map_type*
Type::make_map_type(Type* key_type, Type* val_type, source_location location)
{
  return new Map_type(key_type, val_type, location);
}

// Class Channel_type.

// Hash code.

unsigned int
Channel_type::do_hash_for_method(Gogo* gogo) const
{
  unsigned int ret = 0;
  if (this->may_send_)
    ret += 1;
  if (this->may_receive_)
    ret += 2;
  if (this->element_type_ != NULL)
    ret += this->element_type_->hash_for_method(gogo) << 2;
  return ret << 3;
}

// Whether this type is the same as T.

bool
Channel_type::is_identical(const Channel_type* t,
                           bool errors_are_identical) const
{
  if (!Type::are_identical(this->element_type(), t->element_type(),
                           errors_are_identical, NULL))
    return false;
  return (this->may_send_ == t->may_send_
          && this->may_receive_ == t->may_receive_);
}

// Check whether the parameters for a call to the builtin function
// make are OK for a channel.  A channel can take an optional single
// parameter which is the buffer size.

bool
Channel_type::do_check_make_expression(Expression_list* args,
                                      source_location location)
{
  if (args != NULL && !args->empty())
    {
      if (!Type::check_int_value(args->front(),
                                 _("bad buffer size when making channel"),
                                 location))
        return false;
      else if (args->size() > 1)
        {
          error_at(location, "too many arguments when making channel");
          return false;
        }
    }
  return true;
}

// Return the tree for a channel type.  A channel is a pointer to a
// __go_channel struct.  The __go_channel struct is defined in
// libgo/runtime/channel.h.

Btype*
Channel_type::do_get_backend(Gogo* gogo)
{
  static Btype* backend_channel_type;
  if (backend_channel_type == NULL)
    {
      std::vector<Backend::Btyped_identifier> bfields;
      Btype* bt = gogo->backend()->struct_type(bfields);
      bt = gogo->backend()->named_type("__go_channel", bt, BUILTINS_LOCATION);
      backend_channel_type = gogo->backend()->pointer_type(bt);
    }
  return backend_channel_type;
}

// Handle the builtin function make for a channel.

tree
Channel_type::do_make_expression_tree(Translate_context* context,
                                      Expression_list* args,
                                      source_location location)
{
  Gogo* gogo = context->gogo();
  tree channel_type = type_to_tree(this->get_backend(gogo));

  Type* ptdt = Type::make_type_descriptor_ptr_type();
  tree element_type_descriptor =
    this->element_type_->type_descriptor_pointer(gogo, location);

  tree bad_index = NULL_TREE;

  tree expr_tree;
  if (args == NULL || args->empty())
    expr_tree = size_zero_node;
  else
    {
      expr_tree = args->front()->get_tree(context);
      if (expr_tree == error_mark_node)
        return error_mark_node;
      if (!DECL_P(expr_tree))
        expr_tree = save_expr(expr_tree);
      if (!INTEGRAL_TYPE_P(TREE_TYPE(expr_tree)))
        expr_tree = convert_to_integer(sizetype, expr_tree);
      bad_index = Expression::check_bounds(expr_tree, sizetype, bad_index,
                                           location);
    }

  static tree new_channel_fndecl;
  tree ret = Gogo::call_builtin(&new_channel_fndecl,
                                location,
                                "__go_new_channel",
                                2,
                                channel_type,
                                type_to_tree(ptdt->get_backend(gogo)),
                                element_type_descriptor,
                                sizetype,
                                expr_tree);
  if (ret == error_mark_node)
    return error_mark_node;
  // This can panic if the capacity is out of range.
  TREE_NOTHROW(new_channel_fndecl) = 0;

  if (bad_index == NULL_TREE)
    return ret;
  else
    {
      tree crash = Gogo::runtime_error(RUNTIME_ERROR_MAKE_CHAN_OUT_OF_BOUNDS,
                                       location);
      return build2(COMPOUND_EXPR, TREE_TYPE(ret),
                    build3(COND_EXPR, void_type_node,
                           bad_index, crash, NULL_TREE),
                    ret);
    }
}

// Build a type descriptor for a channel type.

Type*
Channel_type::make_chan_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* tdt = Type::make_type_descriptor_type();
      Type* ptdt = Type::make_type_descriptor_ptr_type();

      Type* uintptr_type = Type::lookup_integer_type("uintptr");

      Struct_type* sf =
        Type::make_builtin_struct_type(3,
                                       "", tdt,
                                       "elem", ptdt,
                                       "dir", uintptr_type);

      ret = Type::make_builtin_named_type("ChanType", sf);
    }

  return ret;
}

// Build a type descriptor for a map type.

Expression*
Channel_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  source_location bloc = BUILTINS_LOCATION;

  Type* ctdt = Channel_type::make_chan_type_descriptor_type();

  const Struct_field_list* fields = ctdt->struct_type()->fields();

  Expression_list* vals = new Expression_list();
  vals->reserve(3);

  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->field_name() == "commonType");
  vals->push_back(this->type_descriptor_constructor(gogo,
                                                    RUNTIME_TYPE_KIND_CHAN,
                                                    name, NULL, true));

  ++p;
  go_assert(p->field_name() == "elem");
  vals->push_back(Expression::make_type_descriptor(this->element_type_, bloc));

  ++p;
  go_assert(p->field_name() == "dir");
  // These bits must match the ones in libgo/runtime/go-type.h.
  int val = 0;
  if (this->may_receive_)
    val |= 1;
  if (this->may_send_)
    val |= 2;
  mpz_t iv;
  mpz_init_set_ui(iv, val);
  vals->push_back(Expression::make_integer(&iv, p->type(), bloc));
  mpz_clear(iv);

  ++p;
  go_assert(p == fields->end());

  return Expression::make_struct_composite_literal(ctdt, vals, bloc);
}

// Reflection string.

void
Channel_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  if (!this->may_send_)
    ret->append("<-");
  ret->append("chan");
  if (!this->may_receive_)
    ret->append("<-");
  ret->push_back(' ');
  this->append_reflection(this->element_type_, gogo, ret);
}

// Mangled name.

void
Channel_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  ret->push_back('C');
  this->append_mangled_name(this->element_type_, gogo, ret);
  if (this->may_send_)
    ret->push_back('s');
  if (this->may_receive_)
    ret->push_back('r');
  ret->push_back('e');
}

// Export.

void
Channel_type::do_export(Export* exp) const
{
  exp->write_c_string("chan ");
  if (this->may_send_ && !this->may_receive_)
    exp->write_c_string("-< ");
  else if (this->may_receive_ && !this->may_send_)
    exp->write_c_string("<- ");
  exp->write_type(this->element_type_);
}

// Import.

Channel_type*
Channel_type::do_import(Import* imp)
{
  imp->require_c_string("chan ");

  bool may_send;
  bool may_receive;
  if (imp->match_c_string("-< "))
    {
      imp->advance(3);
      may_send = true;
      may_receive = false;
    }
  else if (imp->match_c_string("<- "))
    {
      imp->advance(3);
      may_receive = true;
      may_send = false;
    }
  else
    {
      may_send = true;
      may_receive = true;
    }

  Type* element_type = imp->read_type();

  return Type::make_channel_type(may_send, may_receive, element_type);
}

// Make a new channel type.

Channel_type*
Type::make_channel_type(bool send, bool receive, Type* element_type)
{
  return new Channel_type(send, receive, element_type);
}

// Class Interface_type.

// Traversal.

int
Interface_type::do_traverse(Traverse* traverse)
{
  if (this->methods_ == NULL)
    return TRAVERSE_CONTINUE;
  return this->methods_->traverse(traverse);
}

// Finalize the methods.  This handles interface inheritance.

void
Interface_type::finalize_methods()
{
  if (this->methods_ == NULL)
    return;
  std::vector<Named_type*> seen;
  bool is_recursive = false;
  size_t from = 0;
  size_t to = 0;
  while (from < this->methods_->size())
    {
      const Typed_identifier* p = &this->methods_->at(from);
      if (!p->name().empty())
        {
          size_t i;
          for (i = 0; i < to; ++i)
            {
              if (this->methods_->at(i).name() == p->name())
                {
                  error_at(p->location(), "duplicate method %qs",
                           Gogo::message_name(p->name()).c_str());
                  break;
                }
            }
          if (i == to)
            {
              if (from != to)
                this->methods_->set(to, *p);
              ++to;
            }
          ++from;
          continue;
        }

      Interface_type* it = p->type()->interface_type();
      if (it == NULL)
        {
          error_at(p->location(), "interface contains embedded non-interface");
          ++from;
          continue;
        }
      if (it == this)
        {
          if (!is_recursive)
            {
              error_at(p->location(), "invalid recursive interface");
              is_recursive = true;
            }
          ++from;
          continue;
        }

      Named_type* nt = p->type()->named_type();
      if (nt != NULL)
        {
          std::vector<Named_type*>::const_iterator q;
          for (q = seen.begin(); q != seen.end(); ++q)
            {
              if (*q == nt)
                {
                  error_at(p->location(), "inherited interface loop");
                  break;
                }
            }
          if (q != seen.end())
            {
              ++from;
              continue;
            }
          seen.push_back(nt);
        }

      const Typed_identifier_list* methods = it->methods();
      if (methods == NULL)
        {
          ++from;
          continue;
        }
      for (Typed_identifier_list::const_iterator q = methods->begin();
           q != methods->end();
           ++q)
        {
          if (q->name().empty())
            {
              if (q->type()->forwarded() == p->type()->forwarded())
                error_at(p->location(), "interface inheritance loop");
              else
                {
                  size_t i;
                  for (i = from + 1; i < this->methods_->size(); ++i)
                    {
                      const Typed_identifier* r = &this->methods_->at(i);
                      if (r->name().empty()
                          && r->type()->forwarded() == q->type()->forwarded())
                        {
                          error_at(p->location(),
                                   "inherited interface listed twice");
                          break;
                        }
                    }
                  if (i == this->methods_->size())
                    this->methods_->push_back(Typed_identifier(q->name(),
                                                               q->type(),
                                                               p->location()));
                }
            }
          else if (this->find_method(q->name()) == NULL)
            this->methods_->push_back(Typed_identifier(q->name(), q->type(),
                                                       p->location()));
          else
            {
              if (!is_recursive)
                error_at(p->location(), "inherited method %qs is ambiguous",
                         Gogo::message_name(q->name()).c_str());
            }
        }
      ++from;
    }
  if (to == 0)
    {
      delete this->methods_;
      this->methods_ = NULL;
    }
  else
    {
      this->methods_->resize(to);
      this->methods_->sort_by_name();
    }
}

// Return the method NAME, or NULL.

const Typed_identifier*
Interface_type::find_method(const std::string& name) const
{
  if (this->methods_ == NULL)
    return NULL;
  for (Typed_identifier_list::const_iterator p = this->methods_->begin();
       p != this->methods_->end();
       ++p)
    if (p->name() == name)
      return &*p;
  return NULL;
}

// Return the method index.

size_t
Interface_type::method_index(const std::string& name) const
{
  go_assert(this->methods_ != NULL);
  size_t ret = 0;
  for (Typed_identifier_list::const_iterator p = this->methods_->begin();
       p != this->methods_->end();
       ++p, ++ret)
    if (p->name() == name)
      return ret;
  go_unreachable();
}

// Return whether NAME is an unexported method, for better error
// reporting.

bool
Interface_type::is_unexported_method(Gogo* gogo, const std::string& name) const
{
  if (this->methods_ == NULL)
    return false;
  for (Typed_identifier_list::const_iterator p = this->methods_->begin();
       p != this->methods_->end();
       ++p)
    {
      const std::string& method_name(p->name());
      if (Gogo::is_hidden_name(method_name)
          && name == Gogo::unpack_hidden_name(method_name)
          && gogo->pack_hidden_name(name, false) != method_name)
        return true;
    }
  return false;
}

// Whether this type is identical with T.

bool
Interface_type::is_identical(const Interface_type* t,
                             bool errors_are_identical) const
{
  // We require the same methods with the same types.  The methods
  // have already been sorted.
  if (this->methods() == NULL || t->methods() == NULL)
    return this->methods() == t->methods();

  Typed_identifier_list::const_iterator p1 = this->methods()->begin();
  for (Typed_identifier_list::const_iterator p2 = t->methods()->begin();
       p2 != t->methods()->end();
       ++p1, ++p2)
    {
      if (p1 == this->methods()->end())
        return false;
      if (p1->name() != p2->name()
          || !Type::are_identical(p1->type(), p2->type(),
                                  errors_are_identical, NULL))
        return false;
    }
  if (p1 != this->methods()->end())
    return false;
  return true;
}

// Whether we can assign the interface type T to this type.  The types
// are known to not be identical.  An interface assignment is only
// permitted if T is known to implement all methods in THIS.
// Otherwise a type guard is required.

bool
Interface_type::is_compatible_for_assign(const Interface_type* t,
                                         std::string* reason) const
{
  if (this->methods() == NULL)
    return true;
  for (Typed_identifier_list::const_iterator p = this->methods()->begin();
       p != this->methods()->end();
       ++p)
    {
      const Typed_identifier* m = t->find_method(p->name());
      if (m == NULL)
        {
          if (reason != NULL)
            {
              char buf[200];
              snprintf(buf, sizeof buf,
                       _("need explicit conversion; missing method %s%s%s"),
                       open_quote, Gogo::message_name(p->name()).c_str(),
                       close_quote);
              reason->assign(buf);
            }
          return false;
        }

      std::string subreason;
      if (!Type::are_identical(p->type(), m->type(), true, &subreason))
        {
          if (reason != NULL)
            {
              std::string n = Gogo::message_name(p->name());
              size_t len = 100 + n.length() + subreason.length();
              char* buf = new char[len];
              if (subreason.empty())
                snprintf(buf, len, _("incompatible type for method %s%s%s"),
                         open_quote, n.c_str(), close_quote);
              else
                snprintf(buf, len,
                         _("incompatible type for method %s%s%s (%s)"),
                         open_quote, n.c_str(), close_quote,
                         subreason.c_str());
              reason->assign(buf);
              delete[] buf;
            }
          return false;
        }
    }

  return true;
}

// Hash code.

unsigned int
Interface_type::do_hash_for_method(Gogo* gogo) const
{
  unsigned int ret = 0;
  if (this->methods_ != NULL)
    {
      for (Typed_identifier_list::const_iterator p = this->methods_->begin();
           p != this->methods_->end();
           ++p)
        {
          ret = Type::hash_string(p->name(), ret);
          ret += p->type()->hash_for_method(gogo);
          ret <<= 1;
        }
    }
  return ret;
}

// Return true if T implements the interface.  If it does not, and
// REASON is not NULL, set *REASON to a useful error message.

bool
Interface_type::implements_interface(const Type* t, std::string* reason) const
{
  if (this->methods_ == NULL)
    return true;

  bool is_pointer = false;
  const Named_type* nt = t->named_type();
  const Struct_type* st = t->struct_type();
  // If we start with a named type, we don't dereference it to find
  // methods.
  if (nt == NULL)
    {
      const Type* pt = t->points_to();
      if (pt != NULL)
        {
          // If T is a pointer to a named type, then we need to look at
          // the type to which it points.
          is_pointer = true;
          nt = pt->named_type();
          st = pt->struct_type();
        }
    }

  // If we have a named type, get the methods from it rather than from
  // any struct type.
  if (nt != NULL)
    st = NULL;

  // Only named and struct types have methods.
  if (nt == NULL && st == NULL)
    {
      if (reason != NULL)
        {
          if (t->points_to() != NULL
              && t->points_to()->interface_type() != NULL)
            reason->assign(_("pointer to interface type has no methods"));
          else
            reason->assign(_("type has no methods"));
        }
      return false;
    }

  if (nt != NULL ? !nt->has_any_methods() : !st->has_any_methods())
    {
      if (reason != NULL)
        {
          if (t->points_to() != NULL
              && t->points_to()->interface_type() != NULL)
            reason->assign(_("pointer to interface type has no methods"));
          else
            reason->assign(_("type has no methods"));
        }
      return false;
    }

  for (Typed_identifier_list::const_iterator p = this->methods_->begin();
       p != this->methods_->end();
       ++p)
    {
      bool is_ambiguous = false;
      Method* m = (nt != NULL
                   ? nt->method_function(p->name(), &is_ambiguous)
                   : st->method_function(p->name(), &is_ambiguous));
      if (m == NULL)
        {
          if (reason != NULL)
            {
              std::string n = Gogo::message_name(p->name());
              size_t len = n.length() + 100;
              char* buf = new char[len];
              if (is_ambiguous)
                snprintf(buf, len, _("ambiguous method %s%s%s"),
                         open_quote, n.c_str(), close_quote);
              else
                snprintf(buf, len, _("missing method %s%s%s"),
                         open_quote, n.c_str(), close_quote);
              reason->assign(buf);
              delete[] buf;
            }
          return false;
        }

      Function_type *p_fn_type = p->type()->function_type();
      Function_type* m_fn_type = m->type()->function_type();
      go_assert(p_fn_type != NULL && m_fn_type != NULL);
      std::string subreason;
      if (!p_fn_type->is_identical(m_fn_type, true, true, &subreason))
        {
          if (reason != NULL)
            {
              std::string n = Gogo::message_name(p->name());
              size_t len = 100 + n.length() + subreason.length();
              char* buf = new char[len];
              if (subreason.empty())
                snprintf(buf, len, _("incompatible type for method %s%s%s"),
                         open_quote, n.c_str(), close_quote);
              else
                snprintf(buf, len,
                         _("incompatible type for method %s%s%s (%s)"),
                         open_quote, n.c_str(), close_quote,
                         subreason.c_str());
              reason->assign(buf);
              delete[] buf;
            }
          return false;
        }

      if (!is_pointer && !m->is_value_method())
        {
          if (reason != NULL)
            {
              std::string n = Gogo::message_name(p->name());
              size_t len = 100 + n.length();
              char* buf = new char[len];
              snprintf(buf, len, _("method %s%s%s requires a pointer"),
                       open_quote, n.c_str(), close_quote);
              reason->assign(buf);
              delete[] buf;
            }
          return false;
        }
    }

  return true;
}

// Return the backend representation of the empty interface type.  We
// use the same struct for all empty interfaces.

Btype*
Interface_type::get_backend_empty_interface_type(Gogo* gogo)
{
  static Btype* empty_interface_type;
  if (empty_interface_type == NULL)
    {
      std::vector<Backend::Btyped_identifier> bfields(2);

      Type* pdt = Type::make_type_descriptor_ptr_type();
      bfields[0].name = "__type_descriptor";
      bfields[0].btype = pdt->get_backend(gogo);
      bfields[0].location = UNKNOWN_LOCATION;

      Type* vt = Type::make_pointer_type(Type::make_void_type());
      bfields[1].name = "__object";
      bfields[1].btype = vt->get_backend(gogo);
      bfields[1].location = UNKNOWN_LOCATION;

      empty_interface_type = gogo->backend()->struct_type(bfields);
    }
  return empty_interface_type;
}

// Return the fields of a non-empty interface type.  This is not
// declared in types.h so that types.h doesn't have to #include
// backend.h.

static void
get_backend_interface_fields(Gogo* gogo, Interface_type* type,
                             std::vector<Backend::Btyped_identifier>* bfields)
{
  source_location loc = type->location();

  std::vector<Backend::Btyped_identifier> mfields(type->methods()->size() + 1);

  Type* pdt = Type::make_type_descriptor_ptr_type();
  mfields[0].name = "__type_descriptor";
  mfields[0].btype = pdt->get_backend(gogo);
  mfields[0].location = loc;

  std::string last_name = "";
  size_t i = 1;
  for (Typed_identifier_list::const_iterator p = type->methods()->begin();
       p != type->methods()->end();
       ++p, ++i)
    {
      mfields[i].name = Gogo::unpack_hidden_name(p->name());
      mfields[i].btype = p->type()->get_backend(gogo);
      mfields[i].location = loc;
      // Sanity check: the names should be sorted.
      go_assert(p->name() > last_name);
      last_name = p->name();
    }

  Btype* methods = gogo->backend()->struct_type(mfields);

  bfields->resize(2);

  (*bfields)[0].name = "__methods";
  (*bfields)[0].btype = gogo->backend()->pointer_type(methods);
  (*bfields)[0].location = loc;

  Type* vt = Type::make_pointer_type(Type::make_void_type());
  (*bfields)[1].name = "__object";
  (*bfields)[1].btype = vt->get_backend(gogo);
  (*bfields)[1].location = UNKNOWN_LOCATION;
}

// Return a tree for an interface type.  An interface is a pointer to
// a struct.  The struct has three fields.  The first field is a
// pointer to the type descriptor for the dynamic type of the object.
// The second field is a pointer to a table of methods for the
// interface to be used with the object.  The third field is the value
// of the object itself.

Btype*
Interface_type::do_get_backend(Gogo* gogo)
{
  if (this->methods_ == NULL)
    return Interface_type::get_backend_empty_interface_type(gogo);
  else
    {
      std::vector<Backend::Btyped_identifier> bfields;
      get_backend_interface_fields(gogo, this, &bfields);
      return gogo->backend()->struct_type(bfields);
    }
}

// The type of an interface type descriptor.

Type*
Interface_type::make_interface_type_descriptor_type()
{
  static Type* ret;
  if (ret == NULL)
    {
      Type* tdt = Type::make_type_descriptor_type();
      Type* ptdt = Type::make_type_descriptor_ptr_type();

      Type* string_type = Type::lookup_string_type();
      Type* pointer_string_type = Type::make_pointer_type(string_type);

      Struct_type* sm =
        Type::make_builtin_struct_type(3,
                                       "name", pointer_string_type,
                                       "pkgPath", pointer_string_type,
                                       "typ", ptdt);

      Type* nsm = Type::make_builtin_named_type("imethod", sm);

      Type* slice_nsm = Type::make_array_type(nsm, NULL);

      Struct_type* s = Type::make_builtin_struct_type(2,
                                                      "", tdt,
                                                      "methods", slice_nsm);

      ret = Type::make_builtin_named_type("InterfaceType", s);
    }

  return ret;
}

// Build a type descriptor for an interface type.

Expression*
Interface_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  source_location bloc = BUILTINS_LOCATION;

  Type* itdt = Interface_type::make_interface_type_descriptor_type();

  const Struct_field_list* ifields = itdt->struct_type()->fields();

  Expression_list* ivals = new Expression_list();
  ivals->reserve(2);

  Struct_field_list::const_iterator pif = ifields->begin();
  go_assert(pif->field_name() == "commonType");
  ivals->push_back(this->type_descriptor_constructor(gogo,
                                                     RUNTIME_TYPE_KIND_INTERFACE,
                                                     name, NULL, true));

  ++pif;
  go_assert(pif->field_name() == "methods");

  Expression_list* methods = new Expression_list();
  if (this->methods_ != NULL && !this->methods_->empty())
    {
      Type* elemtype = pif->type()->array_type()->element_type();

      methods->reserve(this->methods_->size());
      for (Typed_identifier_list::const_iterator pm = this->methods_->begin();
           pm != this->methods_->end();
           ++pm)
        {
          const Struct_field_list* mfields = elemtype->struct_type()->fields();

          Expression_list* mvals = new Expression_list();
          mvals->reserve(3);

          Struct_field_list::const_iterator pmf = mfields->begin();
          go_assert(pmf->field_name() == "name");
          std::string s = Gogo::unpack_hidden_name(pm->name());
          Expression* e = Expression::make_string(s, bloc);
          mvals->push_back(Expression::make_unary(OPERATOR_AND, e, bloc));

          ++pmf;
          go_assert(pmf->field_name() == "pkgPath");
          if (!Gogo::is_hidden_name(pm->name()))
            mvals->push_back(Expression::make_nil(bloc));
          else
            {
              s = Gogo::hidden_name_prefix(pm->name());
              e = Expression::make_string(s, bloc);
              mvals->push_back(Expression::make_unary(OPERATOR_AND, e, bloc));
            }

          ++pmf;
          go_assert(pmf->field_name() == "typ");
          mvals->push_back(Expression::make_type_descriptor(pm->type(), bloc));

          ++pmf;
          go_assert(pmf == mfields->end());

          e = Expression::make_struct_composite_literal(elemtype, mvals,
                                                        bloc);
          methods->push_back(e);
        }
    }

  ivals->push_back(Expression::make_slice_composite_literal(pif->type(),
                                                            methods, bloc));

  ++pif;
  go_assert(pif == ifields->end());

  return Expression::make_struct_composite_literal(itdt, ivals, bloc);
}

// Reflection string.

void
Interface_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  ret->append("interface {");
  if (this->methods_ != NULL)
    {
      for (Typed_identifier_list::const_iterator p = this->methods_->begin();
           p != this->methods_->end();
           ++p)
        {
          if (p != this->methods_->begin())
            ret->append(";");
          ret->push_back(' ');
          if (!Gogo::is_hidden_name(p->name()))
            ret->append(p->name());
          else
            {
              // This matches what the gc compiler does.
              std::string prefix = Gogo::hidden_name_prefix(p->name());
              ret->append(prefix.substr(prefix.find('.') + 1));
              ret->push_back('.');
              ret->append(Gogo::unpack_hidden_name(p->name()));
            }
          std::string sub = p->type()->reflection(gogo);
          go_assert(sub.compare(0, 4, "func") == 0);
          sub = sub.substr(4);
          ret->append(sub);
        }
    }
  ret->append(" }");
}

// Mangled name.

void
Interface_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  ret->push_back('I');

  const Typed_identifier_list* methods = this->methods_;
  if (methods != NULL)
    {
      for (Typed_identifier_list::const_iterator p = methods->begin();
           p != methods->end();
           ++p)
        {
          std::string n = Gogo::unpack_hidden_name(p->name());
          char buf[20];
          snprintf(buf, sizeof buf, "%u_",
                   static_cast<unsigned int>(n.length()));
          ret->append(buf);
          ret->append(n);
          this->append_mangled_name(p->type(), gogo, ret);
        }
    }

  ret->push_back('e');
}

// Export.

void
Interface_type::do_export(Export* exp) const
{
  exp->write_c_string("interface { ");

  const Typed_identifier_list* methods = this->methods_;
  if (methods != NULL)
    {
      for (Typed_identifier_list::const_iterator pm = methods->begin();
           pm != methods->end();
           ++pm)
        {
          exp->write_string(pm->name());
          exp->write_c_string(" (");

          const Function_type* fntype = pm->type()->function_type();

          bool first = true;
          const Typed_identifier_list* parameters = fntype->parameters();
          if (parameters != NULL)
            {
              bool is_varargs = fntype->is_varargs();
              for (Typed_identifier_list::const_iterator pp =
                     parameters->begin();
                   pp != parameters->end();
                   ++pp)
                {
                  if (first)
                    first = false;
                  else
                    exp->write_c_string(", ");
                  if (!is_varargs || pp + 1 != parameters->end())
                    exp->write_type(pp->type());
                  else
                    {
                      exp->write_c_string("...");
                      Type *pptype = pp->type();
                      exp->write_type(pptype->array_type()->element_type());
                    }
                }
            }

          exp->write_c_string(")");

          const Typed_identifier_list* results = fntype->results();
          if (results != NULL)
            {
              exp->write_c_string(" ");
              if (results->size() == 1)
                exp->write_type(results->begin()->type());
              else
                {
                  first = true;
                  exp->write_c_string("(");
                  for (Typed_identifier_list::const_iterator p =
                         results->begin();
                       p != results->end();
                       ++p)
                    {
                      if (first)
                        first = false;
                      else
                        exp->write_c_string(", ");
                      exp->write_type(p->type());
                    }
                  exp->write_c_string(")");
                }
            }

          exp->write_c_string("; ");
        }
    }

  exp->write_c_string("}");
}

// Import an interface type.

Interface_type*
Interface_type::do_import(Import* imp)
{
  imp->require_c_string("interface { ");

  Typed_identifier_list* methods = new Typed_identifier_list;
  while (imp->peek_char() != '}')
    {
      std::string name = imp->read_identifier();
      imp->require_c_string(" (");

      Typed_identifier_list* parameters;
      bool is_varargs = false;
      if (imp->peek_char() == ')')
        parameters = NULL;
      else
        {
          parameters = new Typed_identifier_list;
          while (true)
            {
              if (imp->match_c_string("..."))
                {
                  imp->advance(3);
                  is_varargs = true;
                }

              Type* ptype = imp->read_type();
              if (is_varargs)
                ptype = Type::make_array_type(ptype, NULL);
              parameters->push_back(Typed_identifier(Import::import_marker,
                                                     ptype, imp->location()));
              if (imp->peek_char() != ',')
                break;
              go_assert(!is_varargs);
              imp->require_c_string(", ");
            }
        }
      imp->require_c_string(")");

      Typed_identifier_list* results;
      if (imp->peek_char() != ' ')
        results = NULL;
      else
        {
          results = new Typed_identifier_list;
          imp->advance(1);
          if (imp->peek_char() != '(')
            {
              Type* rtype = imp->read_type();
              results->push_back(Typed_identifier(Import::import_marker,
                                                  rtype, imp->location()));
            }
          else
            {
              imp->advance(1);
              while (true)
                {
                  Type* rtype = imp->read_type();
                  results->push_back(Typed_identifier(Import::import_marker,
                                                      rtype, imp->location()));
                  if (imp->peek_char() != ',')
                    break;
                  imp->require_c_string(", ");
                }
              imp->require_c_string(")");
            }
        }

      Function_type* fntype = Type::make_function_type(NULL, parameters,
                                                       results,
                                                       imp->location());
      if (is_varargs)
        fntype->set_is_varargs();
      methods->push_back(Typed_identifier(name, fntype, imp->location()));

      imp->require_c_string("; ");
    }

  imp->require_c_string("}");

  if (methods->empty())
    {
      delete methods;
      methods = NULL;
    }

  return Type::make_interface_type(methods, imp->location());
}

// Make an interface type.

Interface_type*
Type::make_interface_type(Typed_identifier_list* methods,
                          source_location location)
{
  return new Interface_type(methods, location);
}

// Class Method.

// Bind a method to an object.

Expression*
Method::bind_method(Expression* expr, source_location location) const
{
  if (this->stub_ == NULL)
    {
      // When there is no stub object, the binding is determined by
      // the child class.
      return this->do_bind_method(expr, location);
    }

  Expression* func = Expression::make_func_reference(this->stub_, NULL,
                                                     location);
  return Expression::make_bound_method(expr, func, location);
}

// Return the named object associated with a method.  This may only be
// called after methods are finalized.

Named_object*
Method::named_object() const
{
  if (this->stub_ != NULL)
    return this->stub_;
  return this->do_named_object();
}

// Class Named_method.

// The type of the method.

Function_type*
Named_method::do_type() const
{
  if (this->named_object_->is_function())
    return this->named_object_->func_value()->type();
  else if (this->named_object_->is_function_declaration())
    return this->named_object_->func_declaration_value()->type();
  else
    go_unreachable();
}

// Return the location of the method receiver.

source_location
Named_method::do_receiver_location() const
{
  return this->do_type()->receiver()->location();
}

// Bind a method to an object.

Expression*
Named_method::do_bind_method(Expression* expr, source_location location) const
{
  Expression* func = Expression::make_func_reference(this->named_object_, NULL,
                                                     location);
  Bound_method_expression* bme = Expression::make_bound_method(expr, func,
                                                               location);
  // If this is not a local method, and it does not use a stub, then
  // the real method expects a different type.  We need to cast the
  // first argument.
  if (this->depth() > 0 && !this->needs_stub_method())
    {
      Function_type* ftype = this->do_type();
      go_assert(ftype->is_method());
      Type* frtype = ftype->receiver()->type();
      bme->set_first_argument_type(frtype);
    }
  return bme;
}

// Class Interface_method.

// Bind a method to an object.

Expression*
Interface_method::do_bind_method(Expression* expr,
                                 source_location location) const
{
  return Expression::make_interface_field_reference(expr, this->name_,
                                                    location);
}

// Class Methods.

// Insert a new method.  Return true if it was inserted, false
// otherwise.

bool
Methods::insert(const std::string& name, Method* m)
{
  std::pair<Method_map::iterator, bool> ins =
    this->methods_.insert(std::make_pair(name, m));
  if (ins.second)
    return true;
  else
    {
      Method* old_method = ins.first->second;
      if (m->depth() < old_method->depth())
        {
          delete old_method;
          ins.first->second = m;
          return true;
        }
      else
        {
          if (m->depth() == old_method->depth())
            old_method->set_is_ambiguous();
          return false;
        }
    }
}

// Return the number of unambiguous methods.

size_t
Methods::count() const
{
  size_t ret = 0;
  for (Method_map::const_iterator p = this->methods_.begin();
       p != this->methods_.end();
       ++p)
    if (!p->second->is_ambiguous())
      ++ret;
  return ret;
}

// Class Named_type.

// Return the name of the type.

const std::string&
Named_type::name() const
{
  return this->named_object_->name();
}

// Return the name of the type to use in an error message.

std::string
Named_type::message_name() const
{
  return this->named_object_->message_name();
}

// Return the base type for this type.  We have to be careful about
// circular type definitions, which are invalid but may be seen here.

Type*
Named_type::named_base()
{
  if (this->seen_ > 0)
    return this;
  ++this->seen_;
  Type* ret = this->type_->base();
  --this->seen_;
  return ret;
}

const Type*
Named_type::named_base() const
{
  if (this->seen_ > 0)
    return this;
  ++this->seen_;
  const Type* ret = this->type_->base();
  --this->seen_;
  return ret;
}

// Return whether this is an error type.  We have to be careful about
// circular type definitions, which are invalid but may be seen here.

bool
Named_type::is_named_error_type() const
{
  if (this->seen_ > 0)
    return false;
  ++this->seen_;
  bool ret = this->type_->is_error_type();
  --this->seen_;
  return ret;
}

// Add a method to this type.

Named_object*
Named_type::add_method(const std::string& name, Function* function)
{
  if (this->local_methods_ == NULL)
    this->local_methods_ = new Bindings(NULL);
  return this->local_methods_->add_function(name, NULL, function);
}

// Add a method declaration to this type.

Named_object*
Named_type::add_method_declaration(const std::string& name, Package* package,
                                   Function_type* type,
                                   source_location location)
{
  if (this->local_methods_ == NULL)
    this->local_methods_ = new Bindings(NULL);
  return this->local_methods_->add_function_declaration(name, package, type,
                                                        location);
}

// Add an existing method to this type.

void
Named_type::add_existing_method(Named_object* no)
{
  if (this->local_methods_ == NULL)
    this->local_methods_ = new Bindings(NULL);
  this->local_methods_->add_named_object(no);
}

// Look for a local method NAME, and returns its named object, or NULL
// if not there.

Named_object*
Named_type::find_local_method(const std::string& name) const
{
  if (this->local_methods_ == NULL)
    return NULL;
  return this->local_methods_->lookup(name);
}

// Return whether NAME is an unexported field or method, for better
// error reporting.

bool
Named_type::is_unexported_local_method(Gogo* gogo,
                                       const std::string& name) const
{
  Bindings* methods = this->local_methods_;
  if (methods != NULL)
    {
      for (Bindings::const_declarations_iterator p =
             methods->begin_declarations();
           p != methods->end_declarations();
           ++p)
        {
          if (Gogo::is_hidden_name(p->first)
              && name == Gogo::unpack_hidden_name(p->first)
              && gogo->pack_hidden_name(name, false) != p->first)
            return true;
        }
    }
  return false;
}

// Build the complete list of methods for this type, which means
// recursively including all methods for anonymous fields.  Create all
// stub methods.

void
Named_type::finalize_methods(Gogo* gogo)
{
  if (this->all_methods_ != NULL)
    return;

  if (this->local_methods_ != NULL
      && (this->points_to() != NULL || this->interface_type() != NULL))
    {
      const Bindings* lm = this->local_methods_;
      for (Bindings::const_declarations_iterator p = lm->begin_declarations();
           p != lm->end_declarations();
           ++p)
        error_at(p->second->location(),
                 "invalid pointer or interface receiver type");
      delete this->local_methods_;
      this->local_methods_ = NULL;
      return;
    }

  Type::finalize_methods(gogo, this, this->location_, &this->all_methods_);
}

// Return the method NAME, or NULL if there isn't one or if it is
// ambiguous.  Set *IS_AMBIGUOUS if the method exists but is
// ambiguous.

Method*
Named_type::method_function(const std::string& name, bool* is_ambiguous) const
{
  return Type::method_function(this->all_methods_, name, is_ambiguous);
}

// Return a pointer to the interface method table for this type for
// the interface INTERFACE.  IS_POINTER is true if this is for a
// pointer to THIS.

tree
Named_type::interface_method_table(Gogo* gogo, const Interface_type* interface,
                                   bool is_pointer)
{
  go_assert(!interface->is_empty());

  Interface_method_tables** pimt = (is_pointer
                                    ? &this->interface_method_tables_
                                    : &this->pointer_interface_method_tables_);

  if (*pimt == NULL)
    *pimt = new Interface_method_tables(5);

  std::pair<const Interface_type*, tree> val(interface, NULL_TREE);
  std::pair<Interface_method_tables::iterator, bool> ins = (*pimt)->insert(val);

  if (ins.second)
    {
      // This is a new entry in the hash table.
      go_assert(ins.first->second == NULL_TREE);
      ins.first->second = gogo->interface_method_table_for_type(interface,
                                                                this,
                                                                is_pointer);
    }

  tree decl = ins.first->second;
  if (decl == error_mark_node)
    return error_mark_node;
  go_assert(decl != NULL_TREE && TREE_CODE(decl) == VAR_DECL);
  return build_fold_addr_expr(decl);
}

// Return whether a named type has any hidden fields.

bool
Named_type::named_type_has_hidden_fields(std::string* reason) const
{
  if (this->seen_ > 0)
    return false;
  ++this->seen_;
  bool ret = this->type_->has_hidden_fields(this, reason);
  --this->seen_;
  return ret;
}

// Look for a use of a complete type within another type.  This is
// used to check that we don't try to use a type within itself.

class Find_type_use : public Traverse
{
 public:
  Find_type_use(Named_type* find_type)
    : Traverse(traverse_types),
      find_type_(find_type), found_(false)
  { }

  // Whether we found the type.
  bool
  found() const
  { return this->found_; }

 protected:
  int
  type(Type*);

 private:
  // The type we are looking for.
  Named_type* find_type_;
  // Whether we found the type.
  bool found_;
};

// Check for FIND_TYPE in TYPE.

int
Find_type_use::type(Type* type)
{
  if (type->named_type() != NULL && this->find_type_ == type->named_type())
    {
      this->found_ = true;
      return TRAVERSE_EXIT;
    }

  // It's OK if we see a reference to the type in any type which is
  // essentially a pointer: a pointer, a slice, a function, a map, or
  // a channel.
  if (type->points_to() != NULL
      || type->is_open_array_type()
      || type->function_type() != NULL
      || type->map_type() != NULL
      || type->channel_type() != NULL)
    return TRAVERSE_SKIP_COMPONENTS;

  // For an interface, a reference to the type in a method type should
  // be ignored, but we have to consider direct inheritance.  When
  // this is called, there may be cases of direct inheritance
  // represented as a method with no name.
  if (type->interface_type() != NULL)
    {
      const Typed_identifier_list* methods = type->interface_type()->methods();
      if (methods != NULL)
        {
          for (Typed_identifier_list::const_iterator p = methods->begin();
               p != methods->end();
               ++p)
            {
              if (p->name().empty())
                {
                  if (Type::traverse(p->type(), this) == TRAVERSE_EXIT)
                    return TRAVERSE_EXIT;
                }
            }
        }
      return TRAVERSE_SKIP_COMPONENTS;
    }

  // Otherwise, FIND_TYPE_ depends on TYPE, in the sense that we need
  // to convert TYPE to the backend representation before we convert
  // FIND_TYPE_.
  if (type->named_type() != NULL)
    {
      switch (type->base()->classification())
        {
        case Type::TYPE_ERROR:
        case Type::TYPE_BOOLEAN:
        case Type::TYPE_INTEGER:
        case Type::TYPE_FLOAT:
        case Type::TYPE_COMPLEX:
        case Type::TYPE_STRING:
        case Type::TYPE_NIL:
          break;

        case Type::TYPE_ARRAY:
        case Type::TYPE_STRUCT:
          this->find_type_->add_dependency(type->named_type());
          break;

        case Type::TYPE_VOID:
        case Type::TYPE_SINK:
        case Type::TYPE_FUNCTION:
        case Type::TYPE_POINTER:
        case Type::TYPE_CALL_MULTIPLE_RESULT:
        case Type::TYPE_MAP:
        case Type::TYPE_CHANNEL:
        case Type::TYPE_INTERFACE:
        case Type::TYPE_NAMED:
        case Type::TYPE_FORWARD:
        default:
          go_unreachable();
        }
    }

  return TRAVERSE_CONTINUE;
}

// Verify that a named type does not refer to itself.

bool
Named_type::do_verify()
{
  Find_type_use find(this);
  Type::traverse(this->type_, &find);
  if (find.found())
    {
      error_at(this->location_, "invalid recursive type %qs",
               this->message_name().c_str());
      this->is_error_ = true;
      return false;
    }

  // Check whether any of the local methods overloads an existing
  // struct field or interface method.  We don't need to check the
  // list of methods against itself: that is handled by the Bindings
  // code.
  if (this->local_methods_ != NULL)
    {
      Struct_type* st = this->type_->struct_type();
      bool found_dup = false;
      if (st != NULL)
        {
          for (Bindings::const_declarations_iterator p =
                 this->local_methods_->begin_declarations();
               p != this->local_methods_->end_declarations();
               ++p)
            {
              const std::string& name(p->first);
              if (st != NULL && st->find_local_field(name, NULL) != NULL)
                {
                  error_at(p->second->location(),
                           "method %qs redeclares struct field name",
                           Gogo::message_name(name).c_str());
                  found_dup = true;
                }
            }
        }
      if (found_dup)
        return false;
    }

  return true;
}

// Return whether this type is or contains a pointer.

bool
Named_type::do_has_pointer() const
{
  if (this->seen_ > 0)
    return false;
  ++this->seen_;
  bool ret = this->type_->has_pointer();
  --this->seen_;
  return ret;
}

// Return a hash code.  This is used for method lookup.  We simply
// hash on the name itself.

unsigned int
Named_type::do_hash_for_method(Gogo* gogo) const
{
  const std::string& name(this->named_object()->name());
  unsigned int ret = Type::hash_string(name, 0);

  // GOGO will be NULL here when called from Type_hash_identical.
  // That is OK because that is only used for internal hash tables
  // where we are going to be comparing named types for equality.  In
  // other cases, which are cases where the runtime is going to
  // compare hash codes to see if the types are the same, we need to
  // include the package prefix and name in the hash.
  if (gogo != NULL && !Gogo::is_hidden_name(name) && !this->is_builtin())
    {
      const Package* package = this->named_object()->package();
      if (package == NULL)
        {
          ret = Type::hash_string(gogo->unique_prefix(), ret);
          ret = Type::hash_string(gogo->package_name(), ret);
        }
      else
        {
          ret = Type::hash_string(package->unique_prefix(), ret);
          ret = Type::hash_string(package->name(), ret);
        }
    }

  return ret;
}

// Convert a named type to the backend representation.  In order to
// get dependencies right, we fill in a dummy structure for this type,
// then convert all the dependencies, then complete this type.  When
// this function is complete, the size of the type is known.

void
Named_type::convert(Gogo* gogo)
{
  if (this->is_error_ || this->is_converted_)
    return;

  this->create_placeholder(gogo);

  // Convert all the dependencies.  If they refer indirectly back to
  // this type, they will pick up the intermediate tree we just
  // created.
  for (std::vector<Named_type*>::const_iterator p = this->dependencies_.begin();
       p != this->dependencies_.end();
       ++p)
    (*p)->convert(gogo);

  // Complete this type.
  Btype* bt = this->named_btype_;
  Type* base = this->type_->base();
  switch (base->classification())
    {
    case TYPE_VOID:
    case TYPE_BOOLEAN:
    case TYPE_INTEGER:
    case TYPE_FLOAT:
    case TYPE_COMPLEX:
    case TYPE_STRING:
    case TYPE_NIL:
      break;

    case TYPE_MAP:
    case TYPE_CHANNEL:
      break;

    case TYPE_FUNCTION:
    case TYPE_POINTER:
      // The size of these types is already correct.  We don't worry
      // about filling them in until later, when we also track
      // circular references.
      break;

    case TYPE_STRUCT:
      {
        std::vector<Backend::Btyped_identifier> bfields;
        get_backend_struct_fields(gogo, base->struct_type()->fields(),
                                  &bfields);
        if (!gogo->backend()->set_placeholder_struct_type(bt, bfields))
          bt = gogo->backend()->error_type();
      }
      break;

    case TYPE_ARRAY:
      // Slice types were completed in create_placeholder.
      if (!base->is_open_array_type())
        {
          Btype* bet = base->array_type()->get_backend_element(gogo);
          Bexpression* blen = base->array_type()->get_backend_length(gogo);
          if (!gogo->backend()->set_placeholder_array_type(bt, bet, blen))
            bt = gogo->backend()->error_type();
        }
      break;

    case TYPE_INTERFACE:
      // Interface types were completed in create_placeholder.
      break;

    case TYPE_ERROR:
      return;

    default:
    case TYPE_SINK:
    case TYPE_CALL_MULTIPLE_RESULT:
    case TYPE_NAMED:
    case TYPE_FORWARD:
      go_unreachable();
    }

  this->named_btype_ = bt;
  this->is_converted_ = true;
}

// Create the placeholder for a named type.  This is the first step in
// converting to the backend representation.

void
Named_type::create_placeholder(Gogo* gogo)
{
  if (this->is_error_)
    this->named_btype_ = gogo->backend()->error_type();

  if (this->named_btype_ != NULL)
    return;

  // Create the structure for this type.  Note that because we call
  // base() here, we don't attempt to represent a named type defined
  // as another named type.  Instead both named types will point to
  // different base representations.
  Type* base = this->type_->base();
  Btype* bt;
  bool set_name = true;
  switch (base->classification())
    {
    case TYPE_ERROR:
      this->is_error_ = true;
      this->named_btype_ = gogo->backend()->error_type();
      return;

    case TYPE_VOID:
    case TYPE_BOOLEAN:
    case TYPE_INTEGER:
    case TYPE_FLOAT:
    case TYPE_COMPLEX:
    case TYPE_STRING:
    case TYPE_NIL:
      // These are simple basic types, we can just create them
      // directly.
      bt = Type::get_named_base_btype(gogo, base);
      break;

    case TYPE_MAP:
    case TYPE_CHANNEL:
      // All maps and channels have the same backend representation.
      bt = Type::get_named_base_btype(gogo, base);
      break;

    case TYPE_FUNCTION:
    case TYPE_POINTER:
      {
        bool for_function = base->classification() == TYPE_FUNCTION;
        bt = gogo->backend()->placeholder_pointer_type(this->name(),
                                                       this->location_,
                                                       for_function);
        set_name = false;
      }
      break;

    case TYPE_STRUCT:
      bt = gogo->backend()->placeholder_struct_type(this->name(),
                                                    this->location_);
      set_name = false;
      break;

    case TYPE_ARRAY:
      if (base->is_open_array_type())
        bt = gogo->backend()->placeholder_struct_type(this->name(),
                                                      this->location_);
      else
        bt = gogo->backend()->placeholder_array_type(this->name(),
                                                     this->location_);
      set_name = false;
      break;

    case TYPE_INTERFACE:
      if (base->interface_type()->is_empty())
        bt = Interface_type::get_backend_empty_interface_type(gogo);
      else
        {
          bt = gogo->backend()->placeholder_struct_type(this->name(),
                                                        this->location_);
          set_name = false;
        }
      break;

    default:
    case TYPE_SINK:
    case TYPE_CALL_MULTIPLE_RESULT:
    case TYPE_NAMED:
    case TYPE_FORWARD:
      go_unreachable();
    }

  if (set_name)
    bt = gogo->backend()->named_type(this->name(), bt, this->location_);

  this->named_btype_ = bt;

  if (base->is_open_array_type())
    {
      // We do not record slices as dependencies of other types,
      // because we can fill them in completely here with the final
      // size.
      std::vector<Backend::Btyped_identifier> bfields;
      get_backend_slice_fields(gogo, base->array_type(), &bfields);
      if (!gogo->backend()->set_placeholder_struct_type(bt, bfields))
        this->named_btype_ = gogo->backend()->error_type();
    }
  else if (base->interface_type() != NULL
           && !base->interface_type()->is_empty())
    {
      // We do not record interfaces as dependencies of other types,
      // because we can fill them in completely here with the final
      // size.
      std::vector<Backend::Btyped_identifier> bfields;
      get_backend_interface_fields(gogo, base->interface_type(), &bfields);
      if (!gogo->backend()->set_placeholder_struct_type(bt, bfields))
        this->named_btype_ = gogo->backend()->error_type();
    }
}

// Get a tree for a named type.

Btype*
Named_type::do_get_backend(Gogo* gogo)
{
  if (this->is_error_)
    return gogo->backend()->error_type();

  Btype* bt = this->named_btype_;

  if (!gogo->named_types_are_converted())
    {
      // We have not completed converting named types.  NAMED_BTYPE_
      // is a placeholder and we shouldn't do anything further.
      if (bt != NULL)
        return bt;

      // We don't build dependencies for types whose sizes do not
      // change or are not relevant, so we may see them here while
      // converting types.
      this->create_placeholder(gogo);
      bt = this->named_btype_;
      go_assert(bt != NULL);
      return bt;
    }

  // We are not converting types.  This should only be called if the
  // type has already been converted.
  if (!this->is_converted_)
    {
      go_assert(saw_errors());
      return gogo->backend()->error_type();
    }

  go_assert(bt != NULL);

  // Complete the tree.
  Type* base = this->type_->base();
  Btype* bt1;
  switch (base->classification())
    {
    case TYPE_ERROR:
      return gogo->backend()->error_type();

    case TYPE_VOID:
    case TYPE_BOOLEAN:
    case TYPE_INTEGER:
    case TYPE_FLOAT:
    case TYPE_COMPLEX:
    case TYPE_STRING:
    case TYPE_NIL:
    case TYPE_MAP:
    case TYPE_CHANNEL:
    case TYPE_STRUCT:
    case TYPE_ARRAY:
    case TYPE_INTERFACE:
      return bt;

    case TYPE_FUNCTION:
      // Don't build a circular data structure.  GENERIC can't handle
      // it.
      if (this->seen_ > 0)
        {
          this->is_circular_ = true;
          return gogo->backend()->circular_pointer_type(bt, true);
        }
      ++this->seen_;
      bt1 = Type::get_named_base_btype(gogo, base);
      --this->seen_;
      if (this->is_circular_)
        bt1 = gogo->backend()->circular_pointer_type(bt, true);
      if (!gogo->backend()->set_placeholder_function_type(bt, bt1))
        bt = gogo->backend()->error_type();
      return bt;

    case TYPE_POINTER:
      // Don't build a circular data structure. GENERIC can't handle
      // it.
      if (this->seen_ > 0)
        {
          this->is_circular_ = true;
          return gogo->backend()->circular_pointer_type(bt, false);
        }
      ++this->seen_;
      bt1 = Type::get_named_base_btype(gogo, base);
      --this->seen_;
      if (this->is_circular_)
        bt1 = gogo->backend()->circular_pointer_type(bt, false);
      if (!gogo->backend()->set_placeholder_pointer_type(bt, bt1))
        bt = gogo->backend()->error_type();
      return bt;

    default:
    case TYPE_SINK:
    case TYPE_CALL_MULTIPLE_RESULT:
    case TYPE_NAMED:
    case TYPE_FORWARD:
      go_unreachable();
    }

  go_unreachable();
}

// Build a type descriptor for a named type.

Expression*
Named_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  // If NAME is not NULL, then we don't really want the type
  // descriptor for this type; we want the descriptor for the
  // underlying type, giving it the name NAME.
  return this->named_type_descriptor(gogo, this->type_,
                                     name == NULL ? this : name);
}

// Add to the reflection string.  This is used mostly for the name of
// the type used in a type descriptor, not for actual reflection
// strings.

void
Named_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  if (this->location() != BUILTINS_LOCATION)
    {
      const Package* package = this->named_object_->package();
      if (package != NULL)
        ret->append(package->name());
      else
        ret->append(gogo->package_name());
      ret->push_back('.');
    }
  if (this->in_function_ != NULL)
    {
      ret->append(Gogo::unpack_hidden_name(this->in_function_->name()));
      ret->push_back('$');
    }
  ret->append(Gogo::unpack_hidden_name(this->named_object_->name()));
}

// Get the mangled name.

void
Named_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  Named_object* no = this->named_object_;
  std::string name;
  if (this->location() == BUILTINS_LOCATION)
    go_assert(this->in_function_ == NULL);
  else
    {
      const std::string& unique_prefix(no->package() == NULL
                                       ? gogo->unique_prefix()
                                       : no->package()->unique_prefix());
      const std::string& package_name(no->package() == NULL
                                      ? gogo->package_name()
                                      : no->package()->name());
      name = unique_prefix;
      name.append(1, '.');
      name.append(package_name);
      name.append(1, '.');
      if (this->in_function_ != NULL)
        {
          name.append(Gogo::unpack_hidden_name(this->in_function_->name()));
          name.append(1, '$');
        }
    }
  name.append(Gogo::unpack_hidden_name(no->name()));
  char buf[20];
  snprintf(buf, sizeof buf, "N%u_", static_cast<unsigned int>(name.length()));
  ret->append(buf);
  ret->append(name);
}

// Export the type.  This is called to export a global type.

void
Named_type::export_named_type(Export* exp, const std::string&) const
{
  // We don't need to write the name of the type here, because it will
  // be written by Export::write_type anyhow.
  exp->write_c_string("type ");
  exp->write_type(this);
  exp->write_c_string(";\n");
}

// Import a named type.

void
Named_type::import_named_type(Import* imp, Named_type** ptype)
{
  imp->require_c_string("type ");
  Type *type = imp->read_type();
  *ptype = type->named_type();
  go_assert(*ptype != NULL);
  imp->require_c_string(";\n");
}

// Export the type when it is referenced by another type.  In this
// case Export::export_type will already have issued the name.

void
Named_type::do_export(Export* exp) const
{
  exp->write_type(this->type_);

  // To save space, we only export the methods directly attached to
  // this type.
  Bindings* methods = this->local_methods_;
  if (methods == NULL)
    return;

  exp->write_c_string("\n");
  for (Bindings::const_definitions_iterator p = methods->begin_definitions();
       p != methods->end_definitions();
       ++p)
    {
      exp->write_c_string(" ");
      (*p)->export_named_object(exp);
    }

  for (Bindings::const_declarations_iterator p = methods->begin_declarations();
       p != methods->end_declarations();
       ++p)
    {
      if (p->second->is_function_declaration())
        {
          exp->write_c_string(" ");
          p->second->export_named_object(exp);
        }
    }
}

// Make a named type.

Named_type*
Type::make_named_type(Named_object* named_object, Type* type,
                      source_location location)
{
  return new Named_type(named_object, type, location);
}

// Finalize the methods for TYPE.  It will be a named type or a struct
// type.  This sets *ALL_METHODS to the list of methods, and builds
// all required stubs.

void
Type::finalize_methods(Gogo* gogo, const Type* type, source_location location,
                       Methods** all_methods)
{
  *all_methods = NULL;
  Types_seen types_seen;
  Type::add_methods_for_type(type, NULL, 0, false, false, &types_seen,
                             all_methods);
  Type::build_stub_methods(gogo, type, *all_methods, location);
}

// Add the methods for TYPE to *METHODS.  FIELD_INDEXES is used to
// build up the struct field indexes as we go.  DEPTH is the depth of
// the field within TYPE.  IS_EMBEDDED_POINTER is true if we are
// adding these methods for an anonymous field with pointer type.
// NEEDS_STUB_METHOD is true if we need to use a stub method which
// calls the real method.  TYPES_SEEN is used to avoid infinite
// recursion.

void
Type::add_methods_for_type(const Type* type,
                           const Method::Field_indexes* field_indexes,
                           unsigned int depth,
                           bool is_embedded_pointer,
                           bool needs_stub_method,
                           Types_seen* types_seen,
                           Methods** methods)
{
  // Pointer types may not have methods.
  if (type->points_to() != NULL)
    return;

  const Named_type* nt = type->named_type();
  if (nt != NULL)
    {
      std::pair<Types_seen::iterator, bool> ins = types_seen->insert(nt);
      if (!ins.second)
        return;
    }

  if (nt != NULL)
    Type::add_local_methods_for_type(nt, field_indexes, depth,
                                     is_embedded_pointer, needs_stub_method,
                                     methods);

  Type::add_embedded_methods_for_type(type, field_indexes, depth,
                                      is_embedded_pointer, needs_stub_method,
                                      types_seen, methods);

  // If we are called with depth > 0, then we are looking at an
  // anonymous field of a struct.  If such a field has interface type,
  // then we need to add the interface methods.  We don't want to add
  // them when depth == 0, because we will already handle them
  // following the usual rules for an interface type.
  if (depth > 0)
    Type::add_interface_methods_for_type(type, field_indexes, depth, methods);
}

// Add the local methods for the named type NT to *METHODS.  The
// parameters are as for add_methods_to_type.

void
Type::add_local_methods_for_type(const Named_type* nt,
                                 const Method::Field_indexes* field_indexes,
                                 unsigned int depth,
                                 bool is_embedded_pointer,
                                 bool needs_stub_method,
                                 Methods** methods)
{
  const Bindings* local_methods = nt->local_methods();
  if (local_methods == NULL)
    return;

  if (*methods == NULL)
    *methods = new Methods();

  for (Bindings::const_declarations_iterator p =
         local_methods->begin_declarations();
       p != local_methods->end_declarations();
       ++p)
    {
      Named_object* no = p->second;
      bool is_value_method = (is_embedded_pointer
                              || !Type::method_expects_pointer(no));
      Method* m = new Named_method(no, field_indexes, depth, is_value_method,
                                   (needs_stub_method
                                    || (depth > 0 && is_value_method)));
      if (!(*methods)->insert(no->name(), m))
        delete m;
    }
}

// Add the embedded methods for TYPE to *METHODS.  These are the
// methods attached to anonymous fields.  The parameters are as for
// add_methods_to_type.

void
Type::add_embedded_methods_for_type(const Type* type,
                                    const Method::Field_indexes* field_indexes,
                                    unsigned int depth,
                                    bool is_embedded_pointer,
                                    bool needs_stub_method,
                                    Types_seen* types_seen,
                                    Methods** methods)
{
  // Look for anonymous fields in TYPE.  TYPE has fields if it is a
  // struct.
  const Struct_type* st = type->struct_type();
  if (st == NULL)
    return;

  const Struct_field_list* fields = st->fields();
  if (fields == NULL)
    return;

  unsigned int i = 0;
  for (Struct_field_list::const_iterator pf = fields->begin();
       pf != fields->end();
       ++pf, ++i)
    {
      if (!pf->is_anonymous())
        continue;

      Type* ftype = pf->type();
      bool is_pointer = false;
      if (ftype->points_to() != NULL)
        {
          ftype = ftype->points_to();
          is_pointer = true;
        }
      Named_type* fnt = ftype->named_type();
      if (fnt == NULL)
        {
          // This is an error, but it will be diagnosed elsewhere.
          continue;
        }

      Method::Field_indexes* sub_field_indexes = new Method::Field_indexes();
      sub_field_indexes->next = field_indexes;
      sub_field_indexes->field_index = i;

      Type::add_methods_for_type(fnt, sub_field_indexes, depth + 1,
                                 (is_embedded_pointer || is_pointer),
                                 (needs_stub_method
                                  || is_pointer
                                  || i > 0),
                                 types_seen,
                                 methods);
    }
}

// If TYPE is an interface type, then add its method to *METHODS.
// This is for interface methods attached to an anonymous field.  The
// parameters are as for add_methods_for_type.

void
Type::add_interface_methods_for_type(const Type* type,
                                     const Method::Field_indexes* field_indexes,
                                     unsigned int depth,
                                     Methods** methods)
{
  const Interface_type* it = type->interface_type();
  if (it == NULL)
    return;

  const Typed_identifier_list* imethods = it->methods();
  if (imethods == NULL)
    return;

  if (*methods == NULL)
    *methods = new Methods();

  for (Typed_identifier_list::const_iterator pm = imethods->begin();
       pm != imethods->end();
       ++pm)
    {
      Function_type* fntype = pm->type()->function_type();
      if (fntype == NULL)
        {
          // This is an error, but it should be reported elsewhere
          // when we look at the methods for IT.
          continue;
        }
      go_assert(!fntype->is_method());
      fntype = fntype->copy_with_receiver(const_cast<Type*>(type));
      Method* m = new Interface_method(pm->name(), pm->location(), fntype,
                                       field_indexes, depth);
      if (!(*methods)->insert(pm->name(), m))
        delete m;
    }
}

// Build stub methods for TYPE as needed.  METHODS is the set of
// methods for the type.  A stub method may be needed when a type
// inherits a method from an anonymous field.  When we need the
// address of the method, as in a type descriptor, we need to build a
// little stub which does the required field dereferences and jumps to
// the real method.  LOCATION is the location of the type definition.

void
Type::build_stub_methods(Gogo* gogo, const Type* type, const Methods* methods,
                         source_location location)
{
  if (methods == NULL)
    return;
  for (Methods::const_iterator p = methods->begin();
       p != methods->end();
       ++p)
    {
      Method* m = p->second;
      if (m->is_ambiguous() || !m->needs_stub_method())
        continue;

      const std::string& name(p->first);

      // Build a stub method.

      const Function_type* fntype = m->type();

      static unsigned int counter;
      char buf[100];
      snprintf(buf, sizeof buf, "$this%u", counter);
      ++counter;

      Type* receiver_type = const_cast<Type*>(type);
      if (!m->is_value_method())
        receiver_type = Type::make_pointer_type(receiver_type);
      source_location receiver_location = m->receiver_location();
      Typed_identifier* receiver = new Typed_identifier(buf, receiver_type,
                                                        receiver_location);

      const Typed_identifier_list* fnparams = fntype->parameters();
      Typed_identifier_list* stub_params;
      if (fnparams == NULL || fnparams->empty())
        stub_params = NULL;
      else
        {
          // We give each stub parameter a unique name.
          stub_params = new Typed_identifier_list();
          for (Typed_identifier_list::const_iterator pp = fnparams->begin();
               pp != fnparams->end();
               ++pp)
            {
              char pbuf[100];
              snprintf(pbuf, sizeof pbuf, "$p%u", counter);
              stub_params->push_back(Typed_identifier(pbuf, pp->type(),
                                                      pp->location()));
              ++counter;
            }
        }

      const Typed_identifier_list* fnresults = fntype->results();
      Typed_identifier_list* stub_results;
      if (fnresults == NULL || fnresults->empty())
        stub_results = NULL;
      else
        {
          // We create the result parameters without any names, since
          // we won't refer to them.
          stub_results = new Typed_identifier_list();
          for (Typed_identifier_list::const_iterator pr = fnresults->begin();
               pr != fnresults->end();
               ++pr)
            stub_results->push_back(Typed_identifier("", pr->type(),
                                                     pr->location()));
        }

      Function_type* stub_type = Type::make_function_type(receiver,
                                                          stub_params,
                                                          stub_results,
                                                          fntype->location());
      if (fntype->is_varargs())
        stub_type->set_is_varargs();

      // We only create the function in the package which creates the
      // type.
      const Package* package;
      if (type->named_type() == NULL)
        package = NULL;
      else
        package = type->named_type()->named_object()->package();
      Named_object* stub;
      if (package != NULL)
        stub = Named_object::make_function_declaration(name, package,
                                                       stub_type, location);
      else
        {
          stub = gogo->start_function(name, stub_type, false,
                                      fntype->location());
          Type::build_one_stub_method(gogo, m, buf, stub_params,
                                      fntype->is_varargs(), location);
          gogo->finish_function(fntype->location());
        }

      m->set_stub_object(stub);
    }
}

// Build a stub method which adjusts the receiver as required to call
// METHOD.  RECEIVER_NAME is the name we used for the receiver.
// PARAMS is the list of function parameters.

void
Type::build_one_stub_method(Gogo* gogo, Method* method,
                            const char* receiver_name,
                            const Typed_identifier_list* params,
                            bool is_varargs,
                            source_location location)
{
  Named_object* receiver_object = gogo->lookup(receiver_name, NULL);
  go_assert(receiver_object != NULL);

  Expression* expr = Expression::make_var_reference(receiver_object, location);
  expr = Type::apply_field_indexes(expr, method->field_indexes(), location);
  if (expr->type()->points_to() == NULL)
    expr = Expression::make_unary(OPERATOR_AND, expr, location);

  Expression_list* arguments;
  if (params == NULL || params->empty())
    arguments = NULL;
  else
    {
      arguments = new Expression_list();
      for (Typed_identifier_list::const_iterator p = params->begin();
           p != params->end();
           ++p)
        {
          Named_object* param = gogo->lookup(p->name(), NULL);
          go_assert(param != NULL);
          Expression* param_ref = Expression::make_var_reference(param,
                                                                 location);
          arguments->push_back(param_ref);
        }
    }

  Expression* func = method->bind_method(expr, location);
  go_assert(func != NULL);
  Call_expression* call = Expression::make_call(func, arguments, is_varargs,
                                                location);
  size_t count = call->result_count();
  if (count == 0)
    gogo->add_statement(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));
        }
      Statement* retstat = Statement::make_return_statement(retvals, location);
      gogo->add_statement(retstat);
    }
}

// Apply FIELD_INDEXES to EXPR.  The field indexes have to be applied
// in reverse order.

Expression*
Type::apply_field_indexes(Expression* expr,
                          const Method::Field_indexes* field_indexes,
                          source_location location)
{
  if (field_indexes == NULL)
    return expr;
  expr = Type::apply_field_indexes(expr, field_indexes->next, location);
  Struct_type* stype = expr->type()->deref()->struct_type();
  go_assert(stype != NULL
             && field_indexes->field_index < stype->field_count());
  if (expr->type()->struct_type() == NULL)
    {
      go_assert(expr->type()->points_to() != NULL);
      expr = Expression::make_unary(OPERATOR_MULT, expr, location);
      go_assert(expr->type()->struct_type() == stype);
    }
  return Expression::make_field_reference(expr, field_indexes->field_index,
                                          location);
}

// Return whether NO is a method for which the receiver is a pointer.

bool
Type::method_expects_pointer(const Named_object* no)
{
  const Function_type *fntype;
  if (no->is_function())
    fntype = no->func_value()->type();
  else if (no->is_function_declaration())
    fntype = no->func_declaration_value()->type();
  else
    go_unreachable();
  return fntype->receiver()->type()->points_to() != NULL;
}

// Given a set of methods for a type, METHODS, return the method NAME,
// or NULL if there isn't one or if it is ambiguous.  If IS_AMBIGUOUS
// is not NULL, then set *IS_AMBIGUOUS to true if the method exists
// but is ambiguous (and return NULL).

Method*
Type::method_function(const Methods* methods, const std::string& name,
                      bool* is_ambiguous)
{
  if (is_ambiguous != NULL)
    *is_ambiguous = false;
  if (methods == NULL)
    return NULL;
  Methods::const_iterator p = methods->find(name);
  if (p == methods->end())
    return NULL;
  Method* m = p->second;
  if (m->is_ambiguous())
    {
      if (is_ambiguous != NULL)
        *is_ambiguous = true;
      return NULL;
    }
  return m;
}

// Look for field or method NAME for TYPE.  Return an Expression for
// the field or method bound to EXPR.  If there is no such field or
// method, give an appropriate error and return an error expression.

Expression*
Type::bind_field_or_method(Gogo* gogo, const Type* type, Expression* expr,
                           const std::string& name,
                           source_location location)
{
  if (type->deref()->is_error_type())
    return Expression::make_error(location);

  const Named_type* nt = type->deref()->named_type();
  const Struct_type* st = type->deref()->struct_type();
  const Interface_type* it = type->interface_type();

  // If this is a pointer to a pointer, then it is possible that the
  // pointed-to type has methods.
  if (nt == NULL
      && st == NULL
      && it == NULL
      && type->points_to() != NULL
      && type->points_to()->points_to() != NULL)
    {
      expr = Expression::make_unary(OPERATOR_MULT, expr, location);
      type = type->points_to();
      if (type->deref()->is_error_type())
        return Expression::make_error(location);
      nt = type->points_to()->named_type();
      st = type->points_to()->struct_type();
    }

  bool receiver_can_be_pointer = (expr->type()->points_to() != NULL
                                  || expr->is_addressable());
  std::vector<const Named_type*> seen;
  bool is_method = false;
  bool found_pointer_method = false;
  std::string ambig1;
  std::string ambig2;
  if (Type::find_field_or_method(type, name, receiver_can_be_pointer,
                                 &seen, NULL, &is_method,
                                 &found_pointer_method, &ambig1, &ambig2))
    {
      Expression* ret;
      if (!is_method)
        {
          go_assert(st != NULL);
          if (type->struct_type() == NULL)
            {
              go_assert(type->points_to() != NULL);
              expr = Expression::make_unary(OPERATOR_MULT, expr,
                                            location);
              go_assert(expr->type()->struct_type() == st);
            }
          ret = st->field_reference(expr, name, location);
        }
      else if (it != NULL && it->find_method(name) != NULL)
        ret = Expression::make_interface_field_reference(expr, name,
                                                         location);
      else
        {
          Method* m;
          if (nt != NULL)
            m = nt->method_function(name, NULL);
          else if (st != NULL)
            m = st->method_function(name, NULL);
          else
            go_unreachable();
          go_assert(m != NULL);
          if (!m->is_value_method() && expr->type()->points_to() == NULL)
            expr = Expression::make_unary(OPERATOR_AND, expr, location);
          ret = m->bind_method(expr, location);
        }
      go_assert(ret != NULL);
      return ret;
    }
  else
    {
      if (!ambig1.empty())
        error_at(location, "%qs is ambiguous via %qs and %qs",
                 Gogo::message_name(name).c_str(),
                 Gogo::message_name(ambig1).c_str(),
                 Gogo::message_name(ambig2).c_str());
      else if (found_pointer_method)
        error_at(location, "method requires a pointer");
      else if (nt == NULL && st == NULL && it == NULL)
        error_at(location,
                 ("reference to field %qs in object which "
                  "has no fields or methods"),
                 Gogo::message_name(name).c_str());
      else
        {
          bool is_unexported;
          if (!Gogo::is_hidden_name(name))
            is_unexported = false;
          else
            {
              std::string unpacked = Gogo::unpack_hidden_name(name);
              seen.clear();
              is_unexported = Type::is_unexported_field_or_method(gogo, type,
                                                                  unpacked,
                                                                  &seen);
            }
          if (is_unexported)
            error_at(location, "reference to unexported field or method %qs",
                     Gogo::message_name(name).c_str());
          else
            error_at(location, "reference to undefined field or method %qs",
                     Gogo::message_name(name).c_str());
        }
      return Expression::make_error(location);
    }
}

// Look in TYPE for a field or method named NAME, return true if one
// is found.  This looks through embedded anonymous fields and handles
// ambiguity.  If a method is found, sets *IS_METHOD to true;
// otherwise, if a field is found, set it to false.  If
// RECEIVER_CAN_BE_POINTER is false, then the receiver is a value
// whose address can not be taken.  SEEN is used to avoid infinite
// recursion on invalid types.

// When returning false, this sets *FOUND_POINTER_METHOD if we found a
// method we couldn't use because it requires a pointer.  LEVEL is
// used for recursive calls, and can be NULL for a non-recursive call.
// When this function returns false because it finds that the name is
// ambiguous, it will store a path to the ambiguous names in *AMBIG1
// and *AMBIG2.  If the name is not found at all, *AMBIG1 and *AMBIG2
// will be unchanged.

// This function just returns whether or not there is a field or
// method, and whether it is a field or method.  It doesn't build an
// expression to refer to it.  If it is a method, we then look in the
// list of all methods for the type.  If it is a field, the search has
// to be done again, looking only for fields, and building up the
// expression as we go.

bool
Type::find_field_or_method(const Type* type,
                           const std::string& name,
                           bool receiver_can_be_pointer,
                           std::vector<const Named_type*>* seen,
                           int* level,
                           bool* is_method,
                           bool* found_pointer_method,
                           std::string* ambig1,
                           std::string* ambig2)
{
  // Named types can have locally defined methods.
  const Named_type* nt = type->named_type();
  if (nt == NULL && type->points_to() != NULL)
    nt = type->points_to()->named_type();
  if (nt != NULL)
    {
      Named_object* no = nt->find_local_method(name);
      if (no != NULL)
        {
          if (receiver_can_be_pointer || !Type::method_expects_pointer(no))
            {
              *is_method = true;
              return true;
            }

          // Record that we have found a pointer method in order to
          // give a better error message if we don't find anything
          // else.
          *found_pointer_method = true;
        }

      for (std::vector<const Named_type*>::const_iterator p = seen->begin();
           p != seen->end();
           ++p)
        {
          if (*p == nt)
            {
              // We've already seen this type when searching for methods.
              return false;
            }
        }
    }

  // Interface types can have methods.
  const Interface_type* it = type->interface_type();
  if (it != NULL && it->find_method(name) != NULL)
    {
      *is_method = true;
      return true;
    }

  // Struct types can have fields.  They can also inherit fields and
  // methods from anonymous fields.
  const Struct_type* st = type->deref()->struct_type();
  if (st == NULL)
    return false;
  const Struct_field_list* fields = st->fields();
  if (fields == NULL)
    return false;

  if (nt != NULL)
    seen->push_back(nt);

  int found_level = 0;
  bool found_is_method = false;
  std::string found_ambig1;
  std::string found_ambig2;
  const Struct_field* found_parent = NULL;
  for (Struct_field_list::const_iterator pf = fields->begin();
       pf != fields->end();
       ++pf)
    {
      if (pf->field_name() == name)
        {
          *is_method = false;
          if (nt != NULL)
            seen->pop_back();
          return true;
        }

      if (!pf->is_anonymous())
        continue;

      if (pf->type()->deref()->is_error_type()
          || pf->type()->deref()->is_undefined())
        continue;

      Named_type* fnt = pf->type()->named_type();
      if (fnt == NULL)
        fnt = pf->type()->deref()->named_type();
      go_assert(fnt != NULL);

      int sublevel = level == NULL ? 1 : *level + 1;
      bool sub_is_method;
      std::string subambig1;
      std::string subambig2;
      bool subfound = Type::find_field_or_method(fnt,
                                                 name,
                                                 receiver_can_be_pointer,
                                                 seen,
                                                 &sublevel,
                                                 &sub_is_method,
                                                 found_pointer_method,
                                                 &subambig1,
                                                 &subambig2);
      if (!subfound)
        {
          if (!subambig1.empty())
            {
              // The name was found via this field, but is ambiguous.
              // if the ambiguity is lower or at the same level as
              // anything else we have already found, then we want to
              // pass the ambiguity back to the caller.
              if (found_level == 0 || sublevel <= found_level)
                {
                  found_ambig1 = pf->field_name() + '.' + subambig1;
                  found_ambig2 = pf->field_name() + '.' + subambig2;
                  found_level = sublevel;
                }
            }
        }
      else
        {
          // The name was found via this field.  Use the level to see
          // if we want to use this one, or whether it introduces an
          // ambiguity.
          if (found_level == 0 || sublevel < found_level)
            {
              found_level = sublevel;
              found_is_method = sub_is_method;
              found_ambig1.clear();
              found_ambig2.clear();
              found_parent = &*pf;
            }
          else if (sublevel > found_level)
            ;
          else if (found_ambig1.empty())
            {
              // We found an ambiguity.
              go_assert(found_parent != NULL);
              found_ambig1 = found_parent->field_name();
              found_ambig2 = pf->field_name();
            }
          else
            {
              // We found an ambiguity, but we already know of one.
              // Just report the earlier one.
            }
        }
    }

  // Here if we didn't find anything FOUND_LEVEL is 0.  If we found
  // something ambiguous, FOUND_LEVEL is not 0 and FOUND_AMBIG1 and
  // FOUND_AMBIG2 are not empty.  If we found the field, FOUND_LEVEL
  // is not 0 and FOUND_AMBIG1 and FOUND_AMBIG2 are empty.

  if (nt != NULL)
    seen->pop_back();

  if (found_level == 0)
    return false;
  else if (!found_ambig1.empty())
    {
      go_assert(!found_ambig1.empty());
      ambig1->assign(found_ambig1);
      ambig2->assign(found_ambig2);
      if (level != NULL)
        *level = found_level;
      return false;
    }
  else
    {
      if (level != NULL)
        *level = found_level;
      *is_method = found_is_method;
      return true;
    }
}

// Return whether NAME is an unexported field or method for TYPE.

bool
Type::is_unexported_field_or_method(Gogo* gogo, const Type* type,
                                    const std::string& name,
                                    std::vector<const Named_type*>* seen)
{
  const Named_type* nt = type->named_type();
  if (nt == NULL)
    nt = type->deref()->named_type();
  if (nt != NULL)
    {
      if (nt->is_unexported_local_method(gogo, name))
        return true;

      for (std::vector<const Named_type*>::const_iterator p = seen->begin();
           p != seen->end();
           ++p)
        {
          if (*p == nt)
            {
              // We've already seen this type.
              return false;
            }
        }
    }

  const Interface_type* it = type->interface_type();
  if (it != NULL && it->is_unexported_method(gogo, name))
    return true;

  type = type->deref();

  const Struct_type* st = type->struct_type();
  if (st != NULL && st->is_unexported_local_field(gogo, name))
    return true;

  if (st == NULL)
    return false;

  const Struct_field_list* fields = st->fields();
  if (fields == NULL)
    return false;

  if (nt != NULL)
    seen->push_back(nt);

  for (Struct_field_list::const_iterator pf = fields->begin();
       pf != fields->end();
       ++pf)
    {
      if (pf->is_anonymous()
          && !pf->type()->deref()->is_error_type()
          && !pf->type()->deref()->is_undefined())
        {
          Named_type* subtype = pf->type()->named_type();
          if (subtype == NULL)
            subtype = pf->type()->deref()->named_type();
          if (subtype == NULL)
            {
              // This is an error, but it will be diagnosed elsewhere.
              continue;
            }
          if (Type::is_unexported_field_or_method(gogo, subtype, name, seen))
            {
              if (nt != NULL)
                seen->pop_back();
              return true;
            }
        }
    }

  if (nt != NULL)
    seen->pop_back();

  return false;
}

// Class Forward_declaration.

Forward_declaration_type::Forward_declaration_type(Named_object* named_object)
  : Type(TYPE_FORWARD),
    named_object_(named_object->resolve()), warned_(false)
{
  go_assert(this->named_object_->is_unknown()
             || this->named_object_->is_type_declaration());
}

// Return the named object.

Named_object*
Forward_declaration_type::named_object()
{
  return this->named_object_->resolve();
}

const Named_object*
Forward_declaration_type::named_object() const
{
  return this->named_object_->resolve();
}

// Return the name of the forward declared type.

const std::string&
Forward_declaration_type::name() const
{
  return this->named_object()->name();
}

// Warn about a use of a type which has been declared but not defined.

void
Forward_declaration_type::warn() const
{
  Named_object* no = this->named_object_->resolve();
  if (no->is_unknown())
    {
      // The name was not defined anywhere.
      if (!this->warned_)
        {
          error_at(this->named_object_->location(),
                   "use of undefined type %qs",
                   no->message_name().c_str());
          this->warned_ = true;
        }
    }
  else if (no->is_type_declaration())
    {
      // The name was seen as a type, but the type was never defined.
      if (no->type_declaration_value()->using_type())
        {
          error_at(this->named_object_->location(),
                   "use of undefined type %qs",
                   no->message_name().c_str());
          this->warned_ = true;
        }
    }
  else
    {
      // The name was defined, but not as a type.
      if (!this->warned_)
        {
          error_at(this->named_object_->location(), "expected type");
          this->warned_ = true;
        }
    }
}

// Get the base type of a declaration.  This gives an error if the
// type has not yet been defined.

Type*
Forward_declaration_type::real_type()
{
  if (this->is_defined())
    return this->named_object()->type_value();
  else
    {
      this->warn();
      return Type::make_error_type();
    }
}

const Type*
Forward_declaration_type::real_type() const
{
  if (this->is_defined())
    return this->named_object()->type_value();
  else
    {
      this->warn();
      return Type::make_error_type();
    }
}

// Return whether the base type is defined.

bool
Forward_declaration_type::is_defined() const
{
  return this->named_object()->is_type();
}

// Add a method.  This is used when methods are defined before the
// type.

Named_object*
Forward_declaration_type::add_method(const std::string& name,
                                     Function* function)
{
  Named_object* no = this->named_object();
  if (no->is_unknown())
    no->declare_as_type();
  return no->type_declaration_value()->add_method(name, function);
}

// Add a method declaration.  This is used when methods are declared
// before the type.

Named_object*
Forward_declaration_type::add_method_declaration(const std::string& name,
                                                 Function_type* type,
                                                 source_location location)
{
  Named_object* no = this->named_object();
  if (no->is_unknown())
    no->declare_as_type();
  Type_declaration* td = no->type_declaration_value();
  return td->add_method_declaration(name, type, location);
}

// Traversal.

int
Forward_declaration_type::do_traverse(Traverse* traverse)
{
  if (this->is_defined()
      && Type::traverse(this->real_type(), traverse) == TRAVERSE_EXIT)
    return TRAVERSE_EXIT;
  return TRAVERSE_CONTINUE;
}

// Get the backend representation for the type.

Btype*
Forward_declaration_type::do_get_backend(Gogo* gogo)
{
  if (this->is_defined())
    return Type::get_named_base_btype(gogo, this->real_type());

  if (this->warned_)
    return gogo->backend()->error_type();

  // We represent an undefined type as a struct with no fields.  That
  // should work fine for the backend, since the same case can arise
  // in C.
  std::vector<Backend::Btyped_identifier> fields;
  Btype* bt = gogo->backend()->struct_type(fields);
  return gogo->backend()->named_type(this->name(), bt,
                                     this->named_object()->location());
}

// Build a type descriptor for a forwarded type.

Expression*
Forward_declaration_type::do_type_descriptor(Gogo* gogo, Named_type* name)
{
  if (!this->is_defined())
    return Expression::make_nil(BUILTINS_LOCATION);
  else
    {
      Type* t = this->real_type();
      if (name != NULL)
        return this->named_type_descriptor(gogo, t, name);
      else
        return Expression::make_type_descriptor(t, BUILTINS_LOCATION);
    }
}

// The reflection string.

void
Forward_declaration_type::do_reflection(Gogo* gogo, std::string* ret) const
{
  this->append_reflection(this->real_type(), gogo, ret);
}

// The mangled name.

void
Forward_declaration_type::do_mangled_name(Gogo* gogo, std::string* ret) const
{
  if (this->is_defined())
    this->append_mangled_name(this->real_type(), gogo, ret);
  else
    {
      const Named_object* no = this->named_object();
      std::string name;
      if (no->package() == NULL)
        name = gogo->package_name();
      else
        name = no->package()->name();
      name += '.';
      name += Gogo::unpack_hidden_name(no->name());
      char buf[20];
      snprintf(buf, sizeof buf, "N%u_",
               static_cast<unsigned int>(name.length()));
      ret->append(buf);
      ret->append(name);
    }
}

// Export a forward declaration.  This can happen when a defined type
// refers to a type which is only declared (and is presumably defined
// in some other file in the same package).

void
Forward_declaration_type::do_export(Export*) const
{
  // If there is a base type, that should be exported instead of this.
  go_assert(!this->is_defined());

  // We don't output anything.
}

// Make a forward declaration.

Type*
Type::make_forward_declaration(Named_object* named_object)
{
  return new Forward_declaration_type(named_object);
}

// Class Typed_identifier_list.

// Sort the entries by name.

struct Typed_identifier_list_sort
{
 public:
  bool
  operator()(const Typed_identifier& t1, const Typed_identifier& t2) const
  { return t1.name() < t2.name(); }
};

void
Typed_identifier_list::sort_by_name()
{
  std::sort(this->entries_.begin(), this->entries_.end(),
            Typed_identifier_list_sort());
}

// Traverse types.

int
Typed_identifier_list::traverse(Traverse* traverse)
{
  for (Typed_identifier_list::const_iterator p = this->begin();
       p != this->end();
       ++p)
    {
      if (Type::traverse(p->type(), traverse) == TRAVERSE_EXIT)
        return TRAVERSE_EXIT;
    }
  return TRAVERSE_CONTINUE;
}

// Copy the list.

Typed_identifier_list*
Typed_identifier_list::copy() const
{
  Typed_identifier_list* ret = new Typed_identifier_list();
  for (Typed_identifier_list::const_iterator p = this->begin();
       p != this->end();
       ++p)
    ret->push_back(Typed_identifier(p->name(), p->type(), p->location()));
  return ret;
}