Implement deduction guides for `std::deque`

[mclow.lists]

Summary

Based off of http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0433r2.html

[mclow.lists]

I should probably add some tests for the implicit deduction guides, too.

[mclow.lists]

Added tests (and fix!) for the implicit deduction guides.

[mclow.lists]

Committed as r332785

include/deque

     void clear() noexcept;
 };
 
+template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
+   deque(InputIterator, InputIterator, Allocator = Allocator())
+   -> deque<typename iterator_traits<InputIterator>::value_type, Allocator>;
+
 template <class T, class Allocator>
     bool operator==(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
 template <class T, class Allocator>

 {
     __deque_base(const __deque_base& __c);
     __deque_base& operator=(const __deque_base& __c);
+public:
+    typedef _Allocator                               allocator_type;
+    typedef allocator_traits<allocator_type>         __alloc_traits;
+    typedef typename __alloc_traits::size_type       size_type;
 protected:
     typedef _Tp                                      value_type;
-    typedef _Allocator                               allocator_type;
-    typedef allocator_traits<allocator_type>         __alloc_traits;
     typedef value_type&                              reference;
     typedef const value_type&                        const_reference;
-    typedef typename __alloc_traits::size_type       size_type;
     typedef typename __alloc_traits::difference_type difference_type;
     typedef typename __alloc_traits::pointer         pointer;
     typedef typename __alloc_traits::const_pointer   const_pointer;

     typedef __deque_iterator<value_type, const_pointer, const_reference, __map_const_pointer,
                              difference_type>    const_iterator;
 
+protected:
     __map __map_;
     size_type __start_;
     __compressed_pair<size_type, allocator_type> __size_;

     void __move_assign(deque& __c, false_type);
 };
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template<class _InputIterator,
+         class _Alloc = typename std::allocator<typename iterator_traits<_InputIterator>::value_type>,
+         class = typename enable_if<__is_allocator<_Alloc>::value, void>::type
+         >
+deque(_InputIterator, _InputIterator)
+  -> deque<typename iterator_traits<_InputIterator>::value_type, _Alloc>;
+
+template<class _InputIterator,
+         class _Alloc,
+         class = typename enable_if<__is_allocator<_Alloc>::value, void>::type
+         >
+deque(_InputIterator, _InputIterator, _Alloc)
+  -> deque<typename iterator_traits<_InputIterator>::value_type, _Alloc>;
+#endif
+
+
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(size_type __n)
 {

test/std/containers/sequences/deque/deque.cons/deduct.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <array>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// XFAIL: libcpp-no-deduction-guides
+
+
+// template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
+//    deque(InputIterator, InputIterator, Allocator = Allocator())
+//    -> deque<typename iterator_traits<InputIterator>::value_type, Allocator>;
+//
+
+
+#include <deque>
+#include <iterator>
+#include <cassert>
+#include <cstddef>
+#include <climits> // INT_MAX
+
+#include "test_macros.h"
+#include "test_iterators.h"
+#include "test_allocator.h"
+
+struct A {};
+
+int main()
+{
+  
+//  Test the explicit deduction guides
+    {
+    const int arr[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+    std::deque deq(std::begin(arr), std::end(arr));
+
+    static_assert(std::is_same_v<decltype(deq), std::deque<int>>, "");
+    assert(std::equal(deq.begin(), deq.end(), std::begin(arr), std::end(arr)));
+    }
+
+    {
+    const long arr[] = {INT_MAX, 1L + INT_MAX, 2L, 3L };
+    std::deque deq(std::begin(arr), std::end(arr), std::allocator<long>());
+    static_assert(std::is_same_v<decltype(deq)::value_type, long>, "");
+    assert(deq.size() == 4);
+    assert(deq[0] == INT_MAX);
+    assert(deq[1] == 1L + INT_MAX);
+    assert(deq[2] == 2L);
+    }
+    
+//  Test the implicit deduction guides
+
+    {
+//  We don't expect this one to work.
+//  std::deque deq(std::allocator<int>()); // deque (allocator &)
+    }
+
+    {
+    std::deque deq(1, A{}); // deque (size_type, T)
+    static_assert(std::is_same_v<decltype(deq)::value_type, A>, "");
+    static_assert(std::is_same_v<decltype(deq)::allocator_type, std::allocator<A>>, "");
+    assert(deq.size() == 1);
+    }
+
+    {
+    std::deque deq(1, A{}, test_allocator<A>()); // deque (size_type, T, allocator)
+    static_assert(std::is_same_v<decltype(deq)::value_type, A>, "");
+    static_assert(std::is_same_v<decltype(deq)::allocator_type, test_allocator<A>>, "");
+    assert(deq.size() == 1);
+    }
+
+    {
+    std::deque deq{1U, 2U, 3U, 4U, 5U}; // deque(initializer-list)
+    static_assert(std::is_same_v<decltype(deq)::value_type, unsigned>, "");
+    assert(deq.size() == 5);
+    assert(deq[2] == 3U);
+    }
+
+    {
+    std::deque deq({1.0, 2.0, 3.0, 4.0}, test_allocator<double>()); // deque(initializer-list, allocator)
+    static_assert(std::is_same_v<decltype(deq)::value_type, double>, "");
+    static_assert(std::is_same_v<decltype(deq)::allocator_type, test_allocator<double>>, "");
+    assert(deq.size() == 4);
+    assert(deq[3] == 4.0);
+    }
+
+    {
+    std::deque<long double> source;
+    std::deque deq(source); // deque(deque &)
+    static_assert(std::is_same_v<decltype(deq)::value_type, long double>, "");
+    static_assert(std::is_same_v<decltype(deq)::allocator_type, std::allocator<long double>>, "");
+    assert(deq.size() == 0);
+    }
+}