/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_Try_h
#define mozilla_Try_h

#include "mozilla/Result.h"

/**
 * MOZ_TRY(expr) is the C++ equivalent of Rust's `target = try!(expr);`, using
 * gcc's statement expressions [0]. First, it evaluates expr, which must produce
 * a Result value. On success, the result's success value is 'returned' as
 * rvalue. On error, immediately returns the error result. This pattern allows
 * to directly assign the success value:
 *
 * ```
 * SuccessValue val = MOZ_TRY(Func());
 * ```
 *
 * Where `Func()` returns a `Result<SuccessValue, E>` and is called in a
 * function that returns `Result<T, E>`.
 *
 * [0]: https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
 */
#define MOZ_TRY(expr)                                     \
  __extension__({                                         \
    auto mozTryVarTempResult = ::mozilla::ToResult(expr); \
    if (MOZ_UNLIKELY(mozTryVarTempResult.isErr())) {      \
      return mozTryVarTempResult.propagateErr();          \
    }                                                     \
    mozTryVarTempResult.unwrap();                         \
  })
/**
 * MOZ_TRY_VAR(target, expr) is the C++ equivalent of Rust's `target =
 * try!(expr);`. First, it evaluates expr, which must produce a Result value. On
 * success, the result's success value is assigned to target. On error,
 * immediately returns the error result. |target| must be an lvalue.
 *
 * This macro is obsolete and its usages should be replaced with `MOZ_TRY`.
 */
#define MOZ_TRY_VAR(target, expr) (target) = MOZ_TRY(expr);

#endif  // mozilla_Try_h