Validity check simple replacement fields (#4078)

Co-authored-by: A. Jiang <de34@live.cn> Co-authored-by: Casey Carter <cacarter@microsoft.com>
microsoft · Nov 7, 2023 · 085cd7b · 085cd7b
1 parent 900eeac
commit 085cd7b
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Showing 2 changed files with 6 additions and 3 deletions.
diff --git a/stl/inc/format b/stl/inc/format
@@ -3579,7 +3579,10 @@ struct _Format_checker {
     consteval explicit _Format_checker(basic_string_view<_CharT> _Fmt) noexcept
         : _Parse_context(_Fmt, _Num_args), _Parse_funcs{&_Compile_time_parse_format_specs<_Args, _ParseContext>...} {}
     constexpr void _On_text(const _CharT*, const _CharT*) const noexcept {}
-    constexpr void _On_replacement_field(size_t, const _CharT*) const noexcept {}
+    constexpr void _On_replacement_field(const size_t _Id, const _CharT*) const {
+        _ParseContext _Parse_ctx({});
+        (void) _Parse_funcs[_Id](_Parse_ctx);
+    }
     constexpr const _CharT* _On_format_specs(const size_t _Id, const _CharT* _First, const _CharT*) {
         _Parse_context.advance_to(_Parse_context.begin() + (_First - _Parse_context.begin()._Unwrapped()));
         if (_Id < _Num_args) {

diff --git a/tests/std/tests/P0645R10_text_formatting_custom_formatting/test.cpp b/tests/std/tests/P0645R10_text_formatting_custom_formatting/test.cpp
@@ -57,7 +57,7 @@ struct not_const_formattable_type {
 
 template <>
 struct std::formatter<basic_custom_formattable_type, char> {
-    basic_format_parse_context<char>::iterator parse(basic_format_parse_context<char>& parse_ctx) {
+    constexpr basic_format_parse_context<char>::iterator parse(basic_format_parse_context<char>& parse_ctx) {
         if (parse_ctx.begin() != parse_ctx.end()) {
             throw format_error{"only empty specs please"};
         }
@@ -71,7 +71,7 @@ struct std::formatter<basic_custom_formattable_type, char> {
 
 template <>
 struct std::formatter<not_const_formattable_type, char> {
-    basic_format_parse_context<char>::iterator parse(basic_format_parse_context<char>& parse_ctx) {
+    constexpr basic_format_parse_context<char>::iterator parse(basic_format_parse_context<char>& parse_ctx) {
         if (parse_ctx.begin() != parse_ctx.end()) {
             throw format_error{"only empty specs please"};
         }