libcxx/test/std/concepts/concepts.callable/concept.predicate/predicate.subsumption.compile.pass.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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03, c++11, c++14, c++17
  10
  11 // template<class F, class... Args>
  12 // concept predicate;
  13
  14 #include <concepts>
  15
  16 constexpr bool check_subsumption(std::regular_invocable auto) {
  17   return false;
  18 }
  19
  20 // clang-format off
  21 template<class F>
  22 requires std::predicate<F> && true
  23 constexpr bool check_subsumption(F)
  24 {
  25   return true;
  26 }
  27 // clang-format on
  28
  29 static_assert(!check_subsumption([] {}));
  30 static_assert(check_subsumption([] { return true; }));