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//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14
// is_invocable_r
#include <type_traits>
// Non-invocable types
static_assert(!std::is_invocable_r<void, void>::value);
static_assert(!std::is_invocable_r<void, int>::value);
static_assert(!std::is_invocable_r<void, int*>::value);
static_assert(!std::is_invocable_r<void, int&>::value);
static_assert(!std::is_invocable_r<void, int&&>::value);
// Result type matches
template <typename T>
T Return();
static_assert(std::is_invocable_r<int, decltype(Return<int>)>::value);
static_assert(std::is_invocable_r<char, decltype(Return<char>)>::value);
static_assert(std::is_invocable_r<int*, decltype(Return<int*>)>::value);
static_assert(std::is_invocable_r<int&, decltype(Return<int&>)>::value);
static_assert(std::is_invocable_r<int&&, decltype(Return<int&&>)>::value);
// void result type
// Any actual return type should be useable with a result type of void.
static_assert(std::is_invocable_r<void, decltype(Return<void>)>::value);
static_assert(std::is_invocable_r<void, decltype(Return<int>)>::value);
static_assert(std::is_invocable_r<void, decltype(Return<int*>)>::value);
static_assert(std::is_invocable_r<void, decltype(Return<int&>)>::value);
static_assert(std::is_invocable_r<void, decltype(Return<int&&>)>::value);
// const- and volatile-qualified void should work too.
static_assert(std::is_invocable_r<const void, decltype(Return<void>)>::value);
static_assert(std::is_invocable_r<const void, decltype(Return<int>)>::value);
static_assert(std::is_invocable_r<volatile void, decltype(Return<void>)>::value);
static_assert(std::is_invocable_r<volatile void, decltype(Return<int>)>::value);
static_assert(std::is_invocable_r<const volatile void, decltype(Return<void>)>::value);
static_assert(std::is_invocable_r<const volatile void, decltype(Return<int>)>::value);
// Conversion of result type
// It should be possible to use a result type to which the actual return type
// can be converted.
static_assert(std::is_invocable_r<char, decltype(Return<int>)>::value);
static_assert(std::is_invocable_r<const int*, decltype(Return<int*>)>::value);
static_assert(std::is_invocable_r<void*, decltype(Return<int*>)>::value);
static_assert(std::is_invocable_r<const int&, decltype(Return<int>)>::value);
static_assert(std::is_invocable_r<const int&, decltype(Return<int&>)>::value);
static_assert(std::is_invocable_r<const int&, decltype(Return<int&&>)>::value);
static_assert(std::is_invocable_r<const char&, decltype(Return<int>)>::value);
// But not a result type where the conversion doesn't work.
static_assert(!std::is_invocable_r<int, decltype(Return<void>)>::value);
static_assert(!std::is_invocable_r<int, decltype(Return<int*>)>::value);
// Non-moveable result type
// Define a type that can't be move-constructed.
struct CantMove {
CantMove() = default;
CantMove(CantMove&&) = delete;
};
static_assert(!std::is_move_constructible_v<CantMove>);
static_assert(!std::is_copy_constructible_v<CantMove>);
// Define functions that return that type.
CantMove MakeCantMove() { return {}; }
CantMove MakeCantMoveWithArg(int) { return {}; }
// Assumption check: it should be possible to call one of those functions and
// use it to initialize a CantMove object.
CantMove cant_move = MakeCantMove();
// Therefore std::is_invocable_r should agree that they can be invoked to yield
// a CantMove.
static_assert(std::is_invocable_r<CantMove, decltype(MakeCantMove)>::value);
static_assert(std::is_invocable_r<CantMove, decltype(MakeCantMoveWithArg), int>::value);
// Of course it still shouldn't be possible to call one of the functions and get
// back some other type.
static_assert(!std::is_invocable_r<int, decltype(MakeCantMove)>::value);
// And the argument types should still be important.
static_assert(!std::is_invocable_r<CantMove, decltype(MakeCantMove), int>::value);
static_assert(!std::is_invocable_r<CantMove, decltype(MakeCantMoveWithArg)>::value);
// is_invocable_r
// The struct form should be available too, not just the _v variant.
static_assert(std::is_invocable_r<int, decltype(Return<int>)>::value);
static_assert(!std::is_invocable_r<int*, decltype(Return<int>)>::value);
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