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/* go-assert-interface.c -- interface type assertion for Go.

   Copyright 2010 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-alloc.h"

#include "go-assert.h"

#include "go-panic.h"

#include "interface.h"

/* This is called by the compiler to implement a type assertion from

   one interface type to another.  This returns the value that should

   go in the first field of the result tuple.  The result may be an

   empty or a non-empty interface.  */

const void *

__go_assert_interface (const struct __go_type_descriptor *lhs_descriptor,

                       const struct __go_type_descriptor *rhs_descriptor)

{

  const struct __go_interface_type *lhs_interface;

  if (rhs_descriptor == NULL)

    {

      struct __go_empty_interface panic_arg;

      /* A type assertion is not permitted with a nil interface.  */

      newTypeAssertionError (NULL,

                             NULL,

                             lhs_descriptor,

                             NULL,

                             NULL,

                             lhs_descriptor->__reflection,

                             NULL,

                             &panic_arg);

      __go_panic (panic_arg);

    }

  /* A type assertion to an empty interface just returns the object

     descriptor.  */

  __go_assert (lhs_descriptor->__code == GO_INTERFACE);

  lhs_interface = (const struct __go_interface_type *) lhs_descriptor;

  if (lhs_interface->__methods.__count == 0)

    return rhs_descriptor;

  return __go_convert_interface_2 (lhs_descriptor, rhs_descriptor, 0);

}