text: //===----------------------------------------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  // UNSUPPORTED: c++03
  
  // <tuple>
  
  // template <class... Types> class tuple;
  
  // template <class Alloc>
  //   explicit(see-below) tuple(allocator_arg_t, const Alloc& a);
  
  // NOTE: this constructor does not currently support tags derived from
  // allocator_arg_t because libc++ has to deduce the parameter as a template
  // argument. See PR27684 (https://bugs.llvm.org/show_bug.cgi?id=27684)
  
  #include <tuple>
  #include <cassert>
  
  #include "test_macros.h"
  #include "DefaultOnly.h"
  #include "allocators.h"
  #include "../alloc_first.h"
  #include "../alloc_last.h"
  
  template <class T = void>
  struct NonDefaultConstructible {
    constexpr NonDefaultConstructible() {
        static_assert(!std::is_same<T, T>::value, "Default Ctor instantiated");
    }
  
    explicit constexpr NonDefaultConstructible(int) {}
  };
  
  
  struct DerivedFromAllocArgT : std::allocator_arg_t {};
  
  int main(int, char**)
  {
      {
          std::tuple<> t(std::allocator_arg, A1<int>());
      }
      {
          std::tuple<int> t(std::allocator_arg, A1<int>());
          assert(std::get<0>(t) == 0);
      }
      {
          std::tuple<DefaultOnly> t(std::allocator_arg, A1<int>());
          assert(std::get<0>(t) == DefaultOnly());
      }
      {
          assert(!alloc_first::allocator_constructed);
          std::tuple<alloc_first> t(std::allocator_arg, A1<int>(5));
          assert(alloc_first::allocator_constructed);
          assert(std::get<0>(t) == alloc_first());
      }
      {
          assert(!alloc_last::allocator_constructed);
          std::tuple<alloc_last> t(std::allocator_arg, A1<int>(5));
          assert(alloc_last::allocator_constructed);
          assert(std::get<0>(t) == alloc_last());
      }
      {
          alloc_first::allocator_constructed = false;
          std::tuple<DefaultOnly, alloc_first> t(std::allocator_arg, A1<int>(5));
          assert(std::get<0>(t) == DefaultOnly());
          assert(alloc_first::allocator_constructed);
          assert(std::get<1>(t) == alloc_first());
      }
      {
          alloc_first::allocator_constructed = false;
          alloc_last::allocator_constructed = false;
          std::tuple<DefaultOnly, alloc_first, alloc_last> t(std::allocator_arg,
                                                             A1<int>(5));
          assert(std::get<0>(t) == DefaultOnly());
          assert(alloc_first::allocator_constructed);
          assert(std::get<1>(t) == alloc_first());
          assert(alloc_last::allocator_constructed);
          assert(std::get<2>(t) == alloc_last());
      }
      {
          alloc_first::allocator_constructed = false;
          alloc_last::allocator_constructed = false;
          std::tuple<DefaultOnly, alloc_first, alloc_last> t(std::allocator_arg,
                                                             A2<int>(5));
          assert(std::get<0>(t) == DefaultOnly());
          assert(!alloc_first::allocator_constructed);
          assert(std::get<1>(t) == alloc_first());
          assert(!alloc_last::allocator_constructed);
          assert(std::get<2>(t) == alloc_last());
      }
      {
          // Test that the uses-allocator default constructor does not evaluate
          // its SFINAE when it otherwise shouldn't be selected. Do this by
          // using 'NonDefaultConstructible' which will cause a compile error
          // if std::is_default_constructible is evaluated on it.
          using T = NonDefaultConstructible<>;
          T v(42);
          std::tuple<T, T> t(v, v);
          (void)t;
          std::tuple<T, T> t2(42, 42);
          (void)t2;
      }
  
    return 0;
  }
  