[libcxx-commits] [libcxx] p3798: expected::has_error (PR #204826)

[Alex Kremer via libcxx-commits]

================
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++29
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23, c++26
+
+// constexpr bool has_error() const noexcept;
+
+#include <cassert>
+#include <concepts>
+#include <expected>
+#include <type_traits>
+#include <utility>
+
+#include "test_macros.h"
+#include "../../types.h"
+
+// Test noexcept
+template <class T>
+concept HasErrorNoexcept =
+    requires(T t) {
+      { t.has_error() } noexcept;
+    };
+
+struct Foo {};
+static_assert(!HasErrorNoexcept<Foo>);
+
+static_assert(HasErrorNoexcept<std::expected<int, int>>);
+static_assert(HasErrorNoexcept<const std::expected<int, int>>);
+
+constexpr bool test() {
----------------
godexsoft wrote:

The tests are pretty much mirroring `has_value` tests here, simple cases only as `has_error` is implemented in terms of `has_value`.

https://github.com/llvm/llvm-project/pull/204826