libcxx/test/std/utilities/variant/variant.visit/robust_against_adl.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
  10
  11 // XFAIL: availability-bad_variant_access-missing && !no-exceptions
  12
  13 // <variant>
  14 // template <class Visitor, class... Variants>
  15 // constexpr see below visit(Visitor&& vis, Variants&&... vars);
  16
  17 #include <variant>
  18
  19 #include "test_macros.h"
  20
  21 struct Incomplete;
  22 template<class T> struct Holder { T t; };
  23
  24 constexpr bool test(bool do_it)
  25 {
  26     if (do_it) {
  27         std::variant<Holder<Incomplete>*, int> v = nullptr;
  28         std::visit([](auto){}, v);
  29         std::visit([](auto) -> Holder<Incomplete>* { return nullptr; }, v);
  30 #if TEST_STD_VER > 17
  31         std::visit<void>([](auto){}, v);
  32         std::visit<void*>([](auto) -> Holder<Incomplete>* { return nullptr; }, v);
  33 #endif
  34     }
  35     return true;
  36 }
  37
  38 int main(int, char**)
  39 {
  40     test(true);
  41 #if TEST_STD_VER > 17
  42     static_assert(test(true));
  43 #endif
  44     return 0;
  45 }