c2df707666
There are a handful of standard library types that are intended to support CTAD but don't need any explicit deduction guides to do so. This patch adds a dummy deduction guide to those types to suppress -Wctad-maybe-unsupported (which gets emitted in user code). This is a re-application of the original patch by Eric Fiselier in fcd549a7d828 which had been reverted due to reasons lost at this point. I also added the macro to a few more types. Reviving this patch was prompted by the discussion on https://llvm.org/D133425. Differential Revision: https://reviews.llvm.org/D133535
42 lines
1.2 KiB
C++
42 lines
1.2 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03, c++11, c++14
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// <variant>
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// template <class ...Types> class variant;
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// Make sure that the implicitly-generated CTAD works.
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// We make sure that it is not ill-formed, however we still produce a warning for
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// this one because explicit construction from a variant using CTAD is ambiguous
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// (in the sense that the programer intent is not clear).
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// ADDITIONAL_COMPILE_FLAGS: -Wno-ctad-maybe-unsupported
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#include <variant>
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#include "test_macros.h"
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int main(int, char**) {
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// This is the motivating example from P0739R0
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{
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std::variant<int, double> v1(3);
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std::variant v2 = v1;
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ASSERT_SAME_TYPE(decltype(v2), std::variant<int, double>);
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}
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{
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std::variant<int, double> v1(3);
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std::variant v2 = std::variant(v1); // Technically valid, but intent is ambiguous!
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ASSERT_SAME_TYPE(decltype(v2), std::variant<int, double>);
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}
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return 0;
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}
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