libcxx/test/std/utilities/optional/optional.object/optional.object.ctor/deduct.verify.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 // <optional>
  12
  13 // template<class T>
  14 //   optional(T) -> optional<T>;
  15
  16 #include <optional>
  17 #include <cassert>
  18
  19 struct A {};
  20
  21 int main(int, char**)
  22 {
  23 //  Test the explicit deduction guides
  24
  25 //  Test the implicit deduction guides
  26     {
  27 //  optional()
  28     std::optional opt;   // expected-error {{no viable constructor or deduction guide for deduction of template arguments of 'optional'}}
  29     }
  30
  31     {
  32 //  optional(nullopt_t)
  33     std::optional opt(std::nullopt);   // expected-error-re@optional:* {{static assertion failed{{.*}}instantiation of optional with nullopt_t is ill-formed}}
  34     }
  35
  36   return 0;
  37 }