[libcxx-commits] [libcxx] [libc++] Implement P2988R12: `std::optional<T&>` (PR #155202)

[A. Jiang via libcxx-commits]

================
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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++26
+
+// optional
+
+#include <optional>
+#include <utility>
+
+struct X {
+  int i;
+
+  X(int j) : i(j) {}
+};
+
+int main(int, char**) {
+  const std::optional<int> _co(1);
+  std::optional<int> _o(1);
+
+  // expected-error-re@*:* 8 {{call to deleted constructor of 'std::optional<{{.*}}>'}}
+  std::optional<const int&> o1{1};                     // optional(U&&)
+  std::optional<const int&> o2{std::optional<int>(1)}; // optional(optional<U>&&)
+  std::optional<const int&> o3{_co};                   // optional(const optional<U>&)
+  std::optional<const int&> o4{_o};                    // optional(optional<U>&)
+  std::optional<const X&> o5{1};                       // optional(U&&)
+  std::optional<const X&> o6{std::optional<int>(1)};   // optional(optional<U>&&)
+  std::optional<const X&> o7{_co};                     // optional(const optional<U>&)
+  std::optional<const X&> o8{_o};                      // optional(optional<U>&)
+}
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frederick-vs-ja wrote:

We conventionally add an empty new line at the end of the file.
```suggestion
}

```

https://github.com/llvm/llvm-project/pull/155202