Index: libcxx/include/vector
===================================================================
--- libcxx/include/vector
+++ libcxx/include/vector
@@ -519,29 +519,14 @@
     vector(size_type __n, const value_type& __x);
     vector(size_type __n, const value_type& __x, const allocator_type& __a);
     template <class _InputIterator>
-        vector(_InputIterator __first,
-               typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
-                                 !__is_cpp17_forward_iterator<_InputIterator>::value &&
-                                 is_constructible<
-                                    value_type,
-                                    typename iterator_traits<_InputIterator>::reference>::value,
-                                 _InputIterator>::type __last);
-    template <class _InputIterator>
-        vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
+        vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a = allocator_type(),
                typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
                                  !__is_cpp17_forward_iterator<_InputIterator>::value &&
                                  is_constructible<
                                     value_type,
                                     typename iterator_traits<_InputIterator>::reference>::value>::type* = 0);
     template <class _ForwardIterator>
-        vector(_ForwardIterator __first,
-               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value &&
-                                 is_constructible<
-                                    value_type,
-                                    typename iterator_traits<_ForwardIterator>::reference>::value,
-                                 _ForwardIterator>::type __last);
-    template <class _ForwardIterator>
-        vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
+        vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a = allocator_type(),
                typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value &&
                                  is_constructible<
                                     value_type,
@@ -1174,31 +1159,14 @@
     }
 }
 
-template <class _Tp, class _Allocator>
-template <class _InputIterator>
-vector<_Tp, _Allocator>::vector(_InputIterator __first,
-       typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
-                         !__is_cpp17_forward_iterator<_InputIterator>::value &&
-                         is_constructible<
-                            value_type,
-                            typename iterator_traits<_InputIterator>::reference>::value,
-                          _InputIterator>::type __last)
-{
-#if _LIBCPP_DEBUG_LEVEL >= 2
-    __get_db()->__insert_c(this);
-#endif
-    for (; __first != __last; ++__first)
-        __emplace_back(*__first);
-}
-
 template <class _Tp, class _Allocator>
 template <class _InputIterator>
 vector<_Tp, _Allocator>::vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
-       typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
-                         !__is_cpp17_forward_iterator<_InputIterator>::value &&
-                         is_constructible<
-                            value_type,
-                            typename iterator_traits<_InputIterator>::reference>::value>::type*)
+                                typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                                !__is_cpp17_forward_iterator<_InputIterator>::value &&
+                                is_constructible<
+                                   value_type,
+                                   typename iterator_traits<_InputIterator>::reference>::value>::type*)
     : __base(__a)
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1208,26 +1176,6 @@
         __emplace_back(*__first);
 }
 
-template <class _Tp, class _Allocator>
-template <class _ForwardIterator>
-vector<_Tp, _Allocator>::vector(_ForwardIterator __first,
-                                typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value &&
-                                is_constructible<
-                                   value_type,
-                                   typename iterator_traits<_ForwardIterator>::reference>::value,
-                                                   _ForwardIterator>::type __last)
-{
-#if _LIBCPP_DEBUG_LEVEL >= 2
-    __get_db()->__insert_c(this);
-#endif
-    size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
-    if (__n > 0)
-    {
-        __vallocate(__n);
-        __construct_at_end(__first, __last, __n);
-    }
-}
-
 template <class _Tp, class _Allocator>
 template <class _ForwardIterator>
 vector<_Tp, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
Index: libcxx/test/std/containers/sequences/vector/vector.cons/construct_iter_iter_alloc.pass.cpp
===================================================================
--- libcxx/test/std/containers/sequences/vector/vector.cons/construct_iter_iter_alloc.pass.cpp
+++ libcxx/test/std/containers/sequences/vector/vector.cons/construct_iter_iter_alloc.pass.cpp
@@ -25,6 +25,17 @@
 #include "container_test_types.h"
 #endif
 
+template <class C, class Iterator>
+void test(Iterator first, Iterator last) {
+  C c(first, last);
+  LIBCPP_ASSERT(c.__invariants());
+  assert(c.size() == static_cast<std::size_t>(std::distance(first, last)));
+  LIBCPP_ASSERT(is_contiguous_container_asan_correct(c));
+  for (typename C::const_iterator i = c.cbegin(), e = c.cend(); i != e;
+       ++i, ++first)
+    assert(*i == *first);
+}
+
 template <class C, class Iterator, class A>
 void test(Iterator first, Iterator last, const A& a) {
   C c(first, last, a);
@@ -82,6 +93,12 @@
         random_access_iterator<const int*>(an), alloc);
     test<std::vector<int, min_allocator<int> > >(a, an, alloc);
     test<std::vector<int, implicit_conv_allocator<int> > >(a, an, nullptr);
+    test<std::vector<int> >({}, input_iterator<const int*>{});
+    test<std::vector<int> >(input_iterator<const int*>{}, {});
+    test<std::vector<int> >({}, forward_iterator<const int*>{});
+    test<std::vector<int> >(forward_iterator<const int*>{}, {});
+
+
   }
 #endif
 }