56 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++1110 11// <functional>12 13// template<class T> struct is_placeholder;14// A program may specialize this template for a program-defined type T15// to have a base characteristic of integral_constant<int, N> with N > 016// to indicate that T should be treated as a placeholder type.17// https://llvm.org/PR5175318 19#include <cassert>20#include <functional>21#include <type_traits>22#include <utility>23 24struct My2 {};25template<> struct std::is_placeholder<My2> : std::integral_constant<int, 2> {};26 27int main(int, char**)28{29 {30 auto f = [](auto x) { return 10*x + 9; };31 My2 place;32 auto bound = std::bind(f, place);33 assert(bound(7, 8) == 89);34 }35 {36 auto f = [](auto x) { return 10*x + 9; };37 const My2 place;38 auto bound = std::bind(f, place);39 assert(bound(7, 8) == 89);40 }41 {42 auto f = [](auto x) { return 10*x + 9; };43 My2 place;44 auto bound = std::bind(f, std::move(place));45 assert(bound(7, 8) == 89);46 }47 {48 auto f = [](auto x) { return 10*x + 9; };49 const My2 place;50 auto bound = std::bind(f, std::move(place));51 assert(bound(7, 8) == 89);52 }53 54 return 0;55}56