add default ctor for node types (#2782)

Co-authored-by: A. Jiang <[email protected]> Co-authored-by: Casey Carter <[email protected]> Co-authored-by: Stephan T. Lavavej <[email protected]>
microsoft · Jun 25, 2022 · 5c2d2ad · 5c2d2ad
1 parent e9f282d
commit 5c2d2ad
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Showing 4 changed files with 12 additions and 10 deletions.
diff --git a/stl/inc/forward_list b/stl/inc/forward_list
@@ -241,9 +241,10 @@ template <class _Value_type, class _Voidptr>
 struct _Flist_node { // forward_list node
     using _Nodeptr = _Rebind_pointer_t<_Voidptr, _Flist_node>;
 
-    _Nodeptr _Next; // successor node
-    _Value_type _Myval; // the stored value
+    _Nodeptr _Next;
+    _Value_type _Myval = _Returns_exactly<_Value_type>(); // fake a viable constructor to workaround GH-2749
 
+    _Flist_node()                   = default;
     _Flist_node(const _Flist_node&) = delete;
     _Flist_node& operator=(const _Flist_node&) = delete;
 

diff --git a/stl/inc/list b/stl/inc/list
@@ -289,8 +289,10 @@ struct _List_node { // list node
     using _Nodeptr   = _Rebind_pointer_t<_Voidptr, _List_node>;
     _Nodeptr _Next; // successor node, or first element if head
     _Nodeptr _Prev; // predecessor node, or last element if head
-    _Value_type _Myval; // the stored value, unused if head
+    _Value_type _Myval = // the stored value, unused if head
+        _Returns_exactly<_Value_type>(); // fake a viable constructor to workaround GH-2749
 
+    _List_node()                  = default;
     _List_node(const _List_node&) = delete;
     _List_node& operator=(const _List_node&) = delete;
 

diff --git a/stl/inc/type_traits b/stl/inc/type_traits
@@ -1218,13 +1218,13 @@ struct _Common_type3<void_t<common_type_t<_Ty1, _Ty2>>, _Ty1, _Ty2, _Rest...>
 template <class _Ty1, class _Ty2, class... _Rest>
 struct common_type<_Ty1, _Ty2, _Rest...> : _Common_type3<void, _Ty1, _Ty2, _Rest...> {};
 
+template <class _Ty>
+_Ty _Returns_exactly() noexcept; // not defined
+
 #if _HAS_CXX20
 template <class, class, template <class> class, template <class> class>
 struct basic_common_reference {};
 
-template <class _Ty>
-_Ty _Returns_exactly() noexcept; // not defined
-
 template <class _From>
 struct _Copy_cv_impl {
     template <class _To>
@@ -1614,9 +1614,6 @@ template <class _From, class _To>
 using is_nothrow_convertible = _Is_nothrow_convertible<_From, _To>;
 #endif // _HAS_CXX20
 
-template <class _Ty>
-_Ty _Returns_exactly() noexcept; // not defined
-
 template <class _From, class _To, class = void>
 struct _Invoke_convertible : false_type {};
 

diff --git a/stl/inc/xtree b/stl/inc/xtree
@@ -328,13 +328,15 @@ struct _Tree_node {
     _Nodeptr _Right; // right subtree, or largest element if head
     char _Color; // _Red or _Black, _Black if head
     char _Isnil; // true only if head (also nil) node; TRANSITION, should be bool
-    value_type _Myval; // the stored value, unused if head
+    value_type _Myval = // the stored value, unused if head
+        _Returns_exactly<value_type>(); // fake a viable constructor to workaround GH-2749
 
     enum _Redbl { // colors for link to parent
         _Red,
         _Black
     };
 
+    _Tree_node()                  = default;
     _Tree_node(const _Tree_node&) = delete;
     _Tree_node& operator=(const _Tree_node&) = delete;