libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.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 // <iterator>
  10
  11 // template<class NotAnIterator>
  12 // struct iterator_traits
  13 // {
  14 // };
  15
  16 #include <iterator>
  17
  18 #include "test_macros.h"
  19
  20 struct not_an_iterator
  21 {
  22 };
  23
  24 template <class T>
  25 struct has_value_type
  26 {
  27 private:
  28     struct two {char lx; char lxx;};
  29     template <class U> static two test(...);
  30     template <class U> static char test(typename U::value_type* = 0);
  31 public:
  32     static const bool value = sizeof(test<T>(0)) == 1;
  33 };
  34
  35 int main(int, char**)
  36 {
  37     typedef std::iterator_traits<not_an_iterator> It;
  38     static_assert(!(has_value_type<It>::value), "");
  39
  40   return 0;
  41 }