implement more of N4258 - Cleaning up noexcept in the standard library. Specifically add new noexcept stuff to vector and string's move-assignment operations

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@245330 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/memory b/include/memory
index df35a07..790a161 100644
--- a/include/memory
+++ b/include/memory
@@ -5574,6 +5574,15 @@
 _LIBCPP_INLINE_VISIBILITY
 void __swap_allocator(_Alloc &, _Alloc &, false_type) _NOEXCEPT {}
 
+template <typename _Alloc, typename _Traits=allocator_traits<_Alloc>>
+struct __noexcept_move_assign_container : public integral_constant<bool, 
+    _Traits::propagate_on_container_move_assignment::value
+#if _LIBCPP_STD_VER > 14
+        || _Traits::is_always_equal::value
+#else
+        && is_nothrow_move_assignable<_Alloc>::value
+#endif
+    > {};
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/include/string b/include/string
index 2c677ce..372522c 100644
--- a/include/string
+++ b/include/string
@@ -115,8 +115,8 @@
     basic_string& operator=(const basic_string& str);
     basic_string& operator=(basic_string&& str)
         noexcept(
-             allocator_type::propagate_on_container_move_assignment::value &&
-             is_nothrow_move_assignable<allocator_type>::value);
+             allocator_type::propagate_on_container_move_assignment::value ||
+             allocator_type::is_always_equal::value ); // C++17
     basic_string& operator=(const value_type* s);
     basic_string& operator=(value_type c);
     basic_string& operator=(initializer_list<value_type>);
@@ -1377,8 +1377,7 @@
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     basic_string& operator=(basic_string&& __str)
-        _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
-                   is_nothrow_move_assignable<allocator_type>::value);
+        _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value));
 #endif
     _LIBCPP_INLINE_VISIBILITY basic_string& operator=(const value_type* __s) {return assign(__s);}
     basic_string& operator=(value_type __c);
@@ -1845,11 +1844,16 @@
 
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
-    void __move_assign(basic_string& __str, false_type);
+    void __move_assign(basic_string& __str, false_type)
+        _NOEXCEPT_(__alloc_traits::is_always_equal::value);
     _LIBCPP_INLINE_VISIBILITY
     void __move_assign(basic_string& __str, true_type)
+#if _LIBCPP_STD_VER > 14
+        _NOEXCEPT;
+#else
         _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
 #endif
+#endif
 
     _LIBCPP_INLINE_VISIBILITY
     void
@@ -2430,6 +2434,7 @@
 inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, false_type)
+    _NOEXCEPT_(__alloc_traits::is_always_equal::value)
 {
     if (__alloc() != __str.__alloc())
         assign(__str);
@@ -2441,7 +2446,11 @@
 inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, true_type)
+#if _LIBCPP_STD_VER > 14
+    _NOEXCEPT
+#else
     _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
+#endif
 {
     clear();
     shrink_to_fit();
@@ -2454,8 +2463,7 @@
 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::operator=(basic_string&& __str)
-    _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
-               is_nothrow_move_assignable<allocator_type>::value)
+    _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value))
 {
     __move_assign(__str, integral_constant<bool,
           __alloc_traits::propagate_on_container_move_assignment::value>());
diff --git a/include/vector b/include/vector
index 049d3c8..1cafae1 100644
--- a/include/vector
+++ b/include/vector
@@ -51,8 +51,8 @@
     vector& operator=(const vector& x);
     vector& operator=(vector&& x)
         noexcept(
-             allocator_type::propagate_on_container_move_assignment::value &&
-             is_nothrow_move_assignable<allocator_type>::value);
+             allocator_type::propagate_on_container_move_assignment::value ||
+             allocator_type::is_always_equal::value); // C++17
     vector& operator=(initializer_list<value_type> il);
     template <class InputIterator>
         void assign(InputIterator first, InputIterator last);
@@ -175,8 +175,8 @@
     vector& operator=(const vector& x);
     vector& operator=(vector&& x)
         noexcept(
-             allocator_type::propagate_on_container_move_assignment::value &&
-             is_nothrow_move_assignable<allocator_type>::value);
+             allocator_type::propagate_on_container_move_assignment::value ||
+             allocator_type::is_always_equal::value); // C++17
     vector& operator=(initializer_list<value_type> il);
     template <class InputIterator>
         void assign(InputIterator first, InputIterator last);
@@ -562,9 +562,7 @@
     vector(vector&& __x, const allocator_type& __a);
     _LIBCPP_INLINE_VISIBILITY
     vector& operator=(vector&& __x)
-        _NOEXCEPT_(
-             __alloc_traits::propagate_on_container_move_assignment::value &&
-             is_nothrow_move_assignable<allocator_type>::value);
+        _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value));
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 #ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
@@ -787,7 +785,8 @@
     void __move_range(pointer __from_s, pointer __from_e, pointer __to);
     void __move_assign(vector& __c, true_type)
         _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
-    void __move_assign(vector& __c, false_type);
+    void __move_assign(vector& __c, false_type)
+        _NOEXCEPT_(__alloc_traits::is_always_equal::value);
     _LIBCPP_INLINE_VISIBILITY
     void __destruct_at_end(pointer __new_last) _NOEXCEPT
     {
@@ -1303,9 +1302,7 @@
 inline _LIBCPP_INLINE_VISIBILITY
 vector<_Tp, _Allocator>&
 vector<_Tp, _Allocator>::operator=(vector&& __x)
-        _NOEXCEPT_(
-             __alloc_traits::propagate_on_container_move_assignment::value &&
-             is_nothrow_move_assignable<allocator_type>::value)
+    _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value))
 {
     __move_assign(__x, integral_constant<bool,
           __alloc_traits::propagate_on_container_move_assignment::value>());
@@ -1315,6 +1312,7 @@
 template <class _Tp, class _Allocator>
 void
 vector<_Tp, _Allocator>::__move_assign(vector& __c, false_type)
+    _NOEXCEPT_(__alloc_traits::is_always_equal::value)
 {
     if (__base::__alloc() != __c.__alloc())
     {
@@ -2213,9 +2211,7 @@
     vector(vector&& __v, const allocator_type& __a);
     _LIBCPP_INLINE_VISIBILITY
     vector& operator=(vector&& __v)
-        _NOEXCEPT_(
-             __alloc_traits::propagate_on_container_move_assignment::value &&
-             is_nothrow_move_assignable<allocator_type>::value);
+        _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value));
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 #ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
@@ -2838,9 +2834,7 @@
 inline _LIBCPP_INLINE_VISIBILITY
 vector<bool, _Allocator>&
 vector<bool, _Allocator>::operator=(vector&& __v)
-        _NOEXCEPT_(
-             __alloc_traits::propagate_on_container_move_assignment::value &&
-             is_nothrow_move_assignable<allocator_type>::value)
+    _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value))
 {
     __move_assign(__v, integral_constant<bool,
           __storage_traits::propagate_on_container_move_assignment::value>());