libcxx/test/std/strings/string.view/string.view.io/stream_insert_decl_present.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 // <string>
  10
  11 // template<class charT, class traits, class Allocator>
  12 //   basic_ostream<charT, traits>&
  13 //   operator<<(basic_ostream<charT, traits>& os,
  14 //              const basic_string_view<charT,traits> str);
  15
  16 #include <string_view>
  17 #include <iosfwd>
  18
  19 template <class SV, class = void>
  20 struct HasDecl : std::false_type {};
  21 template <class SV>
  22 struct HasDecl<SV, decltype(static_cast<void>(std::declval<std::ostream&>() << std::declval<SV&>()))> : std::true_type {};
  23
  24 static_assert(HasDecl<std::string_view>::value, "streaming operator declaration not present");