[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_slice_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_slice_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_slice_type()
          || lhs->map_type() != NULL
          || lhs->channel_type() != NULL
          || lhs->function_type() != NULL))
    return true;

  return false;
}

// Return true if a value with type T1 may be compared with a value of
// type T2.  IS_EQUALITY_OP is true for == or !=, false for <, etc.

bool
Type::are_compatible_for_comparison(bool is_equality_op, const Type *t1,
                                    const Type *t2, std::string *reason)
{
  if (t1 != t2
      && !Type::are_assignable(t1, t2, NULL)
      && !Type::are_assignable(t2, t1, NULL))
    {
      if (reason != NULL)
        *reason = "incompatible types in binary expression";
      return false;
    }

  if (!is_equality_op)
    {
      if (t1->integer_type() == NULL
          && t1->float_type() == NULL
          && !t1->is_string_type())
        {
          if (reason != NULL)
            *reason = _("invalid comparison of non-ordered type");
          return false;
        }
    }
  else if (t1->is_slice_type()
           || t1->map_type() != NULL
           || t1->function_type() != NULL
           || t2->is_slice_type()
           || t2->map_type() != NULL
           || t2->function_type() != NULL)
    {
      if (!t1->is_nil_type() && !t2->is_nil_type())
        {
          if (reason != NULL)
            {
              if (t1->is_slice_type() || t2->is_slice_type())
                *reason = _("slice can only be compared to nil");
              else if (t1->map_type() != NULL || t2->map_type() != NULL)
                *reason = _("map can only be compared to nil");
              else
                *reason = _("func can only be compared to nil");

              // Match 6g error messages.
              if (t1->interface_type() != NULL || t2->interface_type() != NULL)
                {
                  char buf[200];
                  snprintf(buf, sizeof buf, _("invalid operation (%s)"),
                           reason->c_str());
                  *reason = buf;
                }
            }
          return false;
        }
    }
  else
    {
      if (!t1->is_boolean_type()
          && t1->integer_type() == NULL
          && t1->float_type() == NULL
          && t1->complex_type() == NULL
          && !t1->is_string_type()
          && t1->points_to() == NULL
          && t1->channel_type() == NULL
          && t1->interface_type() == NULL
          && t1->struct_type() == NULL
          && t1->array_type() == NULL
          && !t1->is_nil_type())
        {
          if (reason != NULL)
            *reason = _("invalid comparison of non-comparable type");
          return false;
        }

      if (t1->named_type() != NULL)
        return t1->named_type()->named_type_is_comparable(reason);
      else if (t2->named_type() != NULL)
        return t2->named_type()->named_type_is_comparable(reason);
      else if (t1->struct_type() != NULL)
        {
          const Struct_field_list* fields = t1->struct_type()->fields();
          for (Struct_field_list::const_iterator p = fields->begin();
               p != fields->end();
               ++p)
            {
              if (!p->type()->is_comparable())
                {
                  if (reason != NULL)
                    *reason = _("invalid comparison of non-comparable struct");
                  return false;
                }
            }
        }
      else if (t1->array_type() != NULL)
        {
          if (!t1->array_type()->element_type()->is_comparable())
            {
              if (reason != NULL)
                *reason = _("invalid comparison of non-comparable array");
              return false;
            }
        }
    }

  return true;
}

// 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_slice_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, false, 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_slice_type())
        {
          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_slice_type())
    {
      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;
}

// 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_;
}

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

tree
Type::type_descriptor_pointer(Gogo* gogo, 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.gcc_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 = this->type_descriptor_var_name(gogo, nt);

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

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

  Location loc = nt == NULL ? Linemap::predeclared_location() : nt->location();

  const Package* dummy;
  if (this->type_descriptor_defined_elsewhere(nt, &dummy))
    {
      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.  If NT is not
// NULL, use it to get the name.  Otherwise this is an unnamed type.

std::string
Type::type_descriptor_var_name(Gogo* gogo, Named_type* nt)
{
  if (nt == NULL)
    return "__go_td_" + this->mangled_name(gogo);

  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 true if this type descriptor is defined in a different
// package.  If this returns true it sets *PACKAGE to the package.

bool
Type::type_descriptor_defined_elsewhere(Named_type* nt,
                                        const Package** package)
{
  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.
          *package = nt->named_object()->package();
          return 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.
          *package = this->points_to()->named_type()->named_object()->package();
          return true;
        }
    }
  return false;
}

// 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);

  Location bloc = Linemap::predeclared_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)
{
  Location bloc = Linemap::predeclared_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)
    {
      Location bloc = Linemap::predeclared_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("key", unsafe_pointer_type, bloc));
      params->push_back(Typed_identifier("key_size", 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("key1", unsafe_pointer_type, bloc));
      params->push_back(Typed_identifier("key2", unsafe_pointer_type, bloc));
      params->push_back(Typed_identifier("key_size", 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;
}

// Set *HASH_FN and *EQUAL_FN to the runtime functions which compute a
// hash code for this type and which compare whether two values of
// this type are equal.  If NAME is not NULL it is the name of this
// type.  HASH_FNTYPE and EQUAL_FNTYPE are the types of these
// functions, for convenience; they may be NULL.

void
Type::type_functions(Gogo* gogo, Named_type* name, Function_type* hash_fntype,
                     Function_type* equal_fntype, Named_object** hash_fn,
                     Named_object** equal_fn)
{
  if (hash_fntype == NULL || equal_fntype == NULL)
    {
      Location bloc = Linemap::predeclared_location();

      Type* uintptr_type = Type::lookup_integer_type("uintptr");
      Type* void_type = Type::make_void_type();
      Type* unsafe_pointer_type = Type::make_pointer_type(void_type);

      if (hash_fntype == NULL)
        {
          Typed_identifier_list* params = new Typed_identifier_list();
          params->push_back(Typed_identifier("key", unsafe_pointer_type,
                                             bloc));
          params->push_back(Typed_identifier("key_size", uintptr_type, bloc));

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

          hash_fntype = Type::make_function_type(NULL, params, results, bloc);
        }
      if (equal_fntype == NULL)
        {
          Typed_identifier_list* params = new Typed_identifier_list();
          params->push_back(Typed_identifier("key1", unsafe_pointer_type,
                                             bloc));
          params->push_back(Typed_identifier("key2", unsafe_pointer_type,
                                             bloc));
          params->push_back(Typed_identifier("key_size", uintptr_type, bloc));

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

          equal_fntype = Type::make_function_type(NULL, params, results, bloc);
        }
    }

  const char* hash_fnname;
  const char* equal_fnname;
  if (this->compare_is_identity())
    {
      hash_fnname = "__go_type_hash_identity";
      equal_fnname = "__go_type_equal_identity";
    }
  else if (!this->is_comparable())
    {
      hash_fnname = "__go_type_hash_error";
      equal_fnname = "__go_type_equal_error";
    }
  else
    {
      switch (this->base()->classification())
        {
        case Type::TYPE_ERROR:
        case Type::TYPE_VOID:
        case Type::TYPE_NIL:
        case Type::TYPE_FUNCTION:
        case Type::TYPE_MAP:
          // For these types is_comparable should have returned false.
          go_unreachable();

        case Type::TYPE_BOOLEAN:
        case Type::TYPE_INTEGER:
        case Type::TYPE_POINTER:
        case Type::TYPE_CHANNEL:
          // For these types compare_is_identity should have returned true.
          go_unreachable();

        case Type::TYPE_FLOAT:
          hash_fnname = "__go_type_hash_float";
          equal_fnname = "__go_type_equal_float";
          break;

        case Type::TYPE_COMPLEX:
          hash_fnname = "__go_type_hash_complex";
          equal_fnname = "__go_type_equal_complex";
          break;

        case Type::TYPE_STRING:
          hash_fnname = "__go_type_hash_string";
          equal_fnname = "__go_type_equal_string";
          break;

        case Type::TYPE_STRUCT:
          {
            // This is a struct which can not be compared using a
            // simple identity function.  We need to build a function
            // for comparison.
            this->specific_type_functions(gogo, name, hash_fntype,
                                          equal_fntype, hash_fn, equal_fn);
            return;
          }

        case Type::TYPE_ARRAY:
          if (this->is_slice_type())
            {
              // Type::is_compatible_for_comparison should have
              // returned false.
              go_unreachable();
            }
          else
            {
              // This is an array which can not be compared using a
              // simple identity function.  We need to build a
              // function for comparison.
              this->specific_type_functions(gogo, name, hash_fntype,
                                            equal_fntype, hash_fn, equal_fn);
              return;
            }
          break;

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

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

        default:
          go_unreachable();
        }
    }


  Location bloc = Linemap::predeclared_location();
  *hash_fn = Named_object::make_function_declaration(hash_fnname, NULL,
                                                     hash_fntype, bloc);
  (*hash_fn)->func_declaration_value()->set_asm_name(hash_fnname);
  *equal_fn = Named_object::make_function_declaration(equal_fnname, NULL,
                                                      equal_fntype, bloc);
  (*equal_fn)->func_declaration_value()->set_asm_name(equal_fnname);
}

// A hash table mapping types to the specific hash functions.

Type::Type_functions Type::type_functions_table;

// Handle a type function which is specific to a type: a struct or
// array which can not use an identity comparison.

void
Type::specific_type_functions(Gogo* gogo, Named_type* name,
                              Function_type* hash_fntype,
                              Function_type* equal_fntype,
                              Named_object** hash_fn,
                              Named_object** equal_fn)
{
  Hash_equal_fn fnull(NULL, NULL);
  std::pair<Type*, Hash_equal_fn> val(name != NULL ? name : this, fnull);
  std::pair<Type_functions::iterator, bool> ins =
    Type::type_functions_table.insert(val);
  if (!ins.second)
    {
      // We already have functions for this type
      *hash_fn = ins.first->second.first;
      *equal_fn = ins.first->second.second;
      return;
    }

  std::string base_name;
  if (name == NULL)
    base_name = gogo->pack_hidden_name(this->mangled_name(gogo), false);
  else
    {
      // This name is already hidden or not as appropriate.
      base_name = name->name();
      const Named_object* in_function = name->in_function();
      if (in_function != NULL)
        base_name += '$' + in_function->name();
    }
  std::string hash_name = base_name + "$hash";
  std::string equal_name = base_name + "$equal";

  Location bloc = Linemap::predeclared_location();

  const Package* package = NULL;
  bool is_defined_elsewhere =
    this->type_descriptor_defined_elsewhere(name, &package);
  if (is_defined_elsewhere)
    {
      *hash_fn = Named_object::make_function_declaration(hash_name, package,
                                                         hash_fntype, bloc);
      *equal_fn = Named_object::make_function_declaration(equal_name, package,
                                                          equal_fntype, bloc);
    }
  else
    {
      *hash_fn = gogo->declare_package_function(hash_name, hash_fntype, bloc);
      *equal_fn = gogo->declare_package_function(equal_name, equal_fntype,
                                                 bloc);
    }

  ins.first->second.first = *hash_fn;
  ins.first->second.second = *equal_fn;

  if (!is_defined_elsewhere)
    {
      if (gogo->in_global_scope())
        this->write_specific_type_functions(gogo, name, hash_name, hash_fntype,
                                            equal_name, equal_fntype);
      else
        gogo->queue_specific_type_function(this, name, hash_name, hash_fntype,
                                           equal_name, equal_fntype);
    }
}

// Write the hash and equality functions for a type which needs to be
// written specially.

void
Type::write_specific_type_functions(Gogo* gogo, Named_type* name,
                                    const std::string& hash_name,
                                    Function_type* hash_fntype,
                                    const std::string& equal_name,
                                    Function_type* equal_fntype)
{
  Location bloc = Linemap::predeclared_location();

  Named_object* hash_fn = gogo->start_function(hash_name, hash_fntype, false,
                                               bloc);
  gogo->start_block(bloc);

  if (this->struct_type() != NULL)
    this->struct_type()->write_hash_function(gogo, name, hash_fntype,
                                             equal_fntype);
  else if (this->array_type() != NULL)
    this->array_type()->write_hash_function(gogo, name, hash_fntype,
                                            equal_fntype);
  else
    go_unreachable();

  Block* b = gogo->finish_block(bloc);
  gogo->add_block(b, bloc);
  gogo->lower_block(hash_fn, b);
  gogo->finish_function(bloc);

  Named_object *equal_fn = gogo->start_function(equal_name, equal_fntype,
                                                false, bloc);
  gogo->start_block(bloc);

  if (this->struct_type() != NULL)
    this->struct_type()->write_equal_function(gogo, name);
  else if (this->array_type() != NULL)
    this->array_type()->write_equal_function(gogo, name);
  else
    go_unreachable();

  b = gogo->finish_block(bloc);
  gogo->add_block(b, bloc);
  gogo->lower_block(equal_fn, b);
  gogo->finish_function(bloc);
}

// 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)
{
  Location bloc = Linemap::predeclared_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);

  if (!this->has_pointer())
    runtime_type_kind |= RUNTIME_TYPE_KIND_NO_POINTERS;
  Struct_field_list::const_iterator p = fields->begin();
  go_assert(p->is_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->is_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->is_field_name("fieldAlign"));
  type_info = Expression::TYPE_INFO_FIELD_ALIGNMENT;
  vals->push_back(Expression::make_type_info(this, type_info));

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

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

  ++p;
  go_assert(p->is_field_name("hashfn"));
  Function_type* hash_fntype = p->type()->function_type();

  ++p;
  go_assert(p->is_field_name("equalfn"));
  Function_type* equal_fntype = p->type()->function_type();

  Named_object* hash_fn;
  Named_object* equal_fn;
  this->type_functions(gogo, name, hash_fntype, equal_fntype, &hash_fn,
                       &equal_fn);
  vals->push_back(Expression::make_func_reference(hash_fn, NULL, bloc));
  vals->push_back(Expression::make_func_reference(equal_fn, NULL, bloc));

  ++p;
  go_assert(p->is_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->is_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->is_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
{
  Location bloc = Linemap::predeclared_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->is_field_name("name"));

  ++p;
  go_assert(p->is_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->is_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
{
  Location bloc = Linemap::predeclared_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
{
  Location bloc = Linemap::predeclared_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->is_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->is_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->is_field_name("mtyp"));
  vals->push_back(Expression::make_type_descriptor(nonmethod_type, bloc));

  ++p;
  go_assert(p->is_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->is_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;
}

// Return whether the backend size of the type is known.

bool
Type::is_backend_type_size_known(Gogo* gogo) const
{
  switch (this->classification_)
    {
    case TYPE_ERROR:
    case TYPE_VOID:
    case TYPE_BOOLEAN:
    case TYPE_INTEGER:
    case TYPE_FLOAT:
    case TYPE_COMPLEX:
    case TYPE_STRING:
    case TYPE_FUNCTION:
    case TYPE_POINTER:
    case TYPE_NIL:
    case TYPE_MAP:
    case TYPE_CHANNEL:
    case TYPE_INTERFACE:
      return true;

    case TYPE_STRUCT:
      {
        const Struct_field_list* fields = this->struct_type()->fields();
        for (Struct_field_list::const_iterator pf = fields->begin();
             pf != fields->end();
             ++pf)
          if (!pf->type()->is_backend_type_size_known(gogo))
            return false;
        return true;
      }

    case TYPE_ARRAY:
      {
        const Array_type* at = this->array_type();
        if (at->length() == NULL)
          return true;
        else
          {
            mpz_t ival;
            mpz_init(ival);
            Type* dummy;
            bool length_known = at->length()->integer_constant_value(true,
                                                                     ival,
                                                                     &dummy);
            mpz_clear(ival);
            if (!length_known)
              return false;
            return at->element_type()->is_backend_type_size_known(gogo);
          }
      }

    case TYPE_NAMED:
      return this->named_type()->is_named_backend_type_size_known();

    case TYPE_FORWARD:
      {
        const Forward_declaration_type* fdt = this->forward_declaration_type();
        return fdt->real_type()->is_backend_type_size_known(gogo);
      }

    case TYPE_SINK:
    case TYPE_CALL_MULTIPLE_RESULT:
      go_unreachable();

    default:
      go_unreachable();
    }
}

// If the size of the type can be determined, set *PSIZE to the size
// in bytes and return true.  Otherwise, return false.  This queries
// the backend.

bool
Type::backend_type_size(Gogo* gogo, unsigned int *psize)
{
  Btype* btype = this->get_backend(gogo);
  if (!this->is_backend_type_size_known(gogo))
    return false;
  size_t size = gogo->backend()->type_size(btype);
  *psize = static_cast<unsigned int>(size);
  if (*psize != size)
    return false;
  return true;
}

// If the alignment of the type can be determined, set *PALIGN to
// the alignment in bytes and return true.  Otherwise, return false.

bool
Type::backend_type_align(Gogo* gogo, unsigned int *palign)
{
  Btype* btype = this->get_backend(gogo);
  if (!this->is_backend_type_size_known(gogo))
    return false;
  size_t align = gogo->backend()->type_alignment(btype);
  *palign = static_cast<unsigned int>(align);
  if (*palign != align)
    return false;
  return true;
}

// Like backend_type_align, but return the alignment when used as a
// field.

bool
Type::backend_type_field_align(Gogo* gogo, unsigned int *palign)
{
  Btype* btype = this->get_backend(gogo);
  if (!this->is_backend_type_size_known(gogo))
    return false;
  size_t a = gogo->backend()->type_field_alignment(btype);
  *palign = static_cast<unsigned int>(a);
  if (*palign != a)
    return false;
  return true;
}

// 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:
  bool
  do_compare_is_identity() const
  { return false; }

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

  Expression*
  do_type_descriptor(Gogo*, Named_type*)
  { return Expression::make_error(Linemap::predeclared_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:
  bool
  do_compare_is_identity() const
  { return false; }

  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:
  bool
  do_compare_is_identity() const
  { return true; }

  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,
                            Linemap::predeclared_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,
                            Linemap::predeclared_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,
                            Linemap::predeclared_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,
                            Linemap::predeclared_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 = Linemap::predeclared_location();

      Type* int_type = Type::lookup_integer_type("int");
      fields[1].name = "__length";
      fields[1].btype = int_type->get_backend(gogo);
      fields[1].location = fields[0].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,
                            Linemap::predeclared_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:
  bool
  do_compare_is_identity() const
  { return false; }

  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)
{
  Location bloc = Linemap::predeclared_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->is_field_name("commonType"));
  vals->push_back(this->type_descriptor_constructor(gogo,
                                                    RUNTIME_TYPE_KIND_FUNC,
                                                    name, NULL, true));

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

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

  ++p;
  go_assert(p->is_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)
{
  Location bloc = Linemap::predeclared_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,
                         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
    {
      Location bloc = Linemap::predeclared_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->is_field_name("commonType"));
      vals->push_back(this->type_descriptor_constructor(gogo,
                                                        RUNTIME_TYPE_KIND_PTR,
                                                        name, methods, false));

      ++p;
      go_assert(p->is_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:
  bool
  do_compare_is_identity() const
  { return false; }

  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;
  }

  bool
  do_compare_is_identity() const
  { 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(Linemap::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();
        }
    }
}

// Return whether this field is named NAME.

bool
Struct_field::is_field_name(const std::string& name) const
{
  const std::string& me(this->typed_identifier_.name());
  if (!me.empty())
    return me == name;
  else
    {
      Type* t = this->typed_identifier_.type();
      if (t->points_to() != NULL)
        t = t->points_to();
      Named_type* nt = t->named_type();
      if (nt != NULL && nt->name() == name)
        return true;

      // This is a horrible hack caused by the fact that we don't pack
      // the names of builtin types.  FIXME.
      if (nt != NULL
          && nt->is_builtin()
          && nt->name() == Gogo::unpack_hidden_name(name))
        return true;

      return false;
    }
}

// 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;
}

// Whether comparisons of this struct type are simple identity
// comparisons.

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

// Build identity and hash functions for this struct.

// 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->is_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,
                             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,
                                   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->is_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;
                }
            }