Check make_format_args's preconditions (#3080)

Co-authored-by: Stephan T. Lavavej <stl@nuwen.net> Co-authored-by: Sam Huang <samestimable2016@gmail.com>
microsoft · Oct 12, 2022 · fe9f858 · fe9f858
1 parent 1fe4d43
commit fe9f858
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/stl/inc/format b/stl/inc/format
@@ -3403,11 +3403,17 @@ _EXPORT_STD using wformat_args = basic_format_args<wformat_context>;
 
 _EXPORT_STD template <class _Context = format_context, class... _Args>
 _NODISCARD auto make_format_args(_Args&&... _Vals) {
+    static_assert((_Has_formatter<_Args, _Context> && ...),
+        "Cannot format an argument. To make type T formattable, provide a formatter<T> specialization. "
+        "See N4917 [format.arg.store]/2 and [formatter.requirements].");
     return _Format_arg_store<_Context, _Args...>{_Vals...};
 }
 
 _EXPORT_STD template <class... _Args>
 _NODISCARD auto make_wformat_args(_Args&&... _Vals) {
+    static_assert((_Has_formatter<_Args, wformat_context> && ...),
+        "Cannot format an argument. To make type T formattable, provide a formatter<T> specialization. "
+        "See N4917 [format.arg.store]/2 and [formatter.requirements].");
     return _Format_arg_store<wformat_context, _Args...>{_Vals...};
 }