Try.h (1477B)
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- 2 * vim: set ts=8 sts=2 et sw=2 tw=80: 3 * This Source Code Form is subject to the terms of the Mozilla Public 4 * License, v. 2.0. If a copy of the MPL was not distributed with this 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 6 7 #ifndef mozilla_Try_h 8 #define mozilla_Try_h 9 10 #include "mozilla/Likely.h" 11 #include "mozilla/Result.h" 12 13 /** 14 * MOZ_TRY(expr) is the C++ equivalent of Rust's `target = try!(expr);`, using 15 * gcc's statement expressions [0]. First, it evaluates expr, which must produce 16 * a Result value. On success, the result's success value is 'returned' as 17 * rvalue. On error, immediately returns the error result. This pattern allows 18 * to directly assign the success value: 19 * 20 * ``` 21 * SuccessValue val = MOZ_TRY(Func()); 22 * ``` 23 * 24 * Where `Func()` returns a `Result<SuccessValue, E>` and is called in a 25 * function that returns `Result<T, E>`. 26 * 27 * [0]: https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html 28 */ 29 #define MOZ_TRY(expr) \ 30 __extension__({ \ 31 auto mozTryVarTempResult = ::mozilla::ToResult(expr); \ 32 if (MOZ_UNLIKELY(mozTryVarTempResult.isErr())) { \ 33 return mozTryVarTempResult.propagateErr(); \ 34 } \ 35 mozTryVarTempResult.unwrap(); \ 36 }) 37 38 #endif // mozilla_Try_h