libcxx/test/std/utilities/meta/meta.rel/is_invocable.pass.cpp

//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++98, c++03, c++11, c++14

// type_traits

// is_invocable

// Most testing of is_invocable is done within the [meta.trans.other] result_of
// tests.

#include <type_traits>
#include <functional>
#include <memory>

#include "test_macros.h"

struct Tag {};
struct DerFromTag : Tag {};

struct Implicit {
  Implicit(int) {}
};

struct Explicit {
  explicit Explicit(int) {}
};

struct NotCallableWithInt {
  int operator()(int) = delete;
  int operator()(Tag) { return 42; }
};

int main()
{
    {
        using Fn = int(Tag::*)(int);
        using RFn = int(Tag::*)(int) &&;
        // INVOKE bullet 1, 2 and 3
        {
            // Bullet 1
            static_assert(std::is_invocable<Fn, Tag&, int>::value, "");
            static_assert(std::is_invocable<Fn, DerFromTag&, int>::value, "");
            static_assert(std::is_invocable<RFn, Tag&&, int>::value, "");
            static_assert(!std::is_invocable<RFn, Tag&, int>::value, "");
            static_assert(!std::is_invocable<Fn, Tag&>::value, "");
            static_assert(!std::is_invocable<Fn, Tag const&, int>::value, "");
        }
        {
            // Bullet 2
            using T = std::reference_wrapper<Tag>;
            using DT = std::reference_wrapper<DerFromTag>;
            using CT = std::reference_wrapper<const Tag>;
            static_assert(std::is_invocable<Fn, T&, int>::value, "");
            static_assert(std::is_invocable<Fn, DT&, int>::value, "");
            static_assert(std::is_invocable<Fn, const T&, int>::value, "");
            static_assert(std::is_invocable<Fn, T&&, int>::value, "");
            static_assert(!std::is_invocable<Fn, CT&, int>::value, "");
            static_assert(!std::is_invocable<RFn, T, int>::value, "");
        }
        {
            // Bullet 3
            using T = Tag*;
            using DT = DerFromTag*;
            using CT = const Tag*;
            using ST = std::unique_ptr<Tag>;
            static_assert(std::is_invocable<Fn, T&, int>::value, "");
            static_assert(std::is_invocable<Fn, DT&, int>::value, "");
            static_assert(std::is_invocable<Fn, const T&, int>::value, "");
            static_assert(std::is_invocable<Fn, T&&, int>::value, "");
            static_assert(std::is_invocable<Fn, ST, int>::value, "");
            static_assert(!std::is_invocable<Fn, CT&, int>::value, "");
            static_assert(!std::is_invocable<RFn, T, int>::value, "");
        }
    }
    {
        // Bullets 4, 5 and 6
        using Fn = int (Tag::*);
        static_assert(!std::is_invocable<Fn>::value, "");
        {
            // Bullet 4
            static_assert(std::is_invocable<Fn, Tag&>::value, "");
            static_assert(std::is_invocable<Fn, DerFromTag&>::value, "");
            static_assert(std::is_invocable<Fn, Tag&&>::value, "");
            static_assert(std::is_invocable<Fn, Tag const&>::value, "");
        }
        {
            // Bullet 5
            using T = std::reference_wrapper<Tag>;
            using DT = std::reference_wrapper<DerFromTag>;
            using CT = std::reference_wrapper<const Tag>;
            static_assert(std::is_invocable<Fn, T&>::value, "");
            static_assert(std::is_invocable<Fn, DT&>::value, "");
            static_assert(std::is_invocable<Fn, const T&>::value, "");
            static_assert(std::is_invocable<Fn, T&&>::value, "");
            static_assert(std::is_invocable<Fn, CT&>::value, "");
        }
        {
            // Bullet 6
            using T = Tag*;
            using DT = DerFromTag*;
            using CT = const Tag*;
            using ST = std::unique_ptr<Tag>;
            static_assert(std::is_invocable<Fn, T&>::value, "");
            static_assert(std::is_invocable<Fn, DT&>::value, "");
            static_assert(std::is_invocable<Fn, const T&>::value, "");
            static_assert(std::is_invocable<Fn, T&&>::value, "");
            static_assert(std::is_invocable<Fn, ST>::value, "");
            static_assert(std::is_invocable<Fn, CT&>::value, "");
        }
    }
    {
        // INVOKE bullet 7
        {
            // Function pointer
            using Fp = void(*)(Tag&, int);
            static_assert(std::is_invocable<Fp, Tag&, int>::value, "");
            static_assert(std::is_invocable<Fp, DerFromTag&, int>::value, "");
            static_assert(!std::is_invocable<Fp, const Tag&, int>::value, "");
            static_assert(!std::is_invocable<Fp>::value, "");
            static_assert(!std::is_invocable<Fp, Tag&>::value, "");
        }
        {
            // Function reference
            using Fp = void(&)(Tag&, int);
            static_assert(std::is_invocable<Fp, Tag&, int>::value, "");
            static_assert(std::is_invocable<Fp, DerFromTag&, int>::value, "");
            static_assert(!std::is_invocable<Fp, const Tag&, int>::value, "");
            static_assert(!std::is_invocable<Fp>::value, "");
            static_assert(!std::is_invocable<Fp, Tag&>::value, "");
        }
        {
            // Function object
            using Fn = NotCallableWithInt;
            static_assert(std::is_invocable<Fn, Tag>::value, "");
            static_assert(!std::is_invocable<Fn, int>::value, "");
        }
    }
    {
        // Check that the conversion to the return type is properly checked
        using Fn = int(*)();
        static_assert(std::is_invocable_r<Implicit, Fn>::value, "");
        static_assert(std::is_invocable_r<double, Fn>::value, "");
        static_assert(std::is_invocable_r<const volatile void, Fn>::value, "");
        static_assert(!std::is_invocable_r<Explicit, Fn>::value, "");
    }
    {
        // Check for is_invocable_v
        using Fn = void(*)();
        static_assert(std::is_invocable_v<Fn>, "");
        static_assert(!std::is_invocable_v<Fn, int>, "");
    }
    {
        // Check for is_invocable_r_v
        using Fn = void(*)();
        static_assert(std::is_invocable_r_v<void, Fn>, "");
        static_assert(!std::is_invocable_r_v<int, Fn>, "");
    }
}