42 lines · cpp
1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9// UNSUPPORTED: c++03, c++11, c++1410 11// <variant>12 13// template <class ...Types> class variant;14 15// Make sure that the implicitly-generated CTAD works.16 17// We make sure that it is not ill-formed, however we still produce a warning for18// this one because explicit construction from a variant using CTAD is ambiguous19// (in the sense that the programmer intent is not clear).20// ADDITIONAL_COMPILE_FLAGS(gcc-style-warnings): -Wno-ctad-maybe-unsupported21 22#include <variant>23 24#include "test_macros.h"25 26int main(int, char**) {27 // This is the motivating example from P0739R028 {29 std::variant<int, double> v1(3);30 std::variant v2 = v1;31 ASSERT_SAME_TYPE(decltype(v2), std::variant<int, double>);32 }33 34 {35 std::variant<int, double> v1(3);36 std::variant v2 = std::variant(v1); // Technically valid, but intent is ambiguous!37 ASSERT_SAME_TYPE(decltype(v2), std::variant<int, double>);38 }39 40 return 0;41}42