libstdc++: Optimize basic_format_parse_context::check_dynamic_spec

This change makes the check_dynamic_spec precondition checks slightly
faster to compile, and avoids those checks entirely for the common cases
of calling check_dynamic_spec_integral or check_dynamic_spec_string.

Instead of checking for unique types by keeping counts in an array and
looping over that array, we can just keep a sum of how many valid types
are present, and check that it equals the total number of types in the
pack.

The diagnostic is slightly worse now, because there's only a single
"invalid template argument types" string that appears in the output,
where previously we had either "non-unique template argument type" or
"disallowed template argument type", depending on the failure mode.
Given that most users will never use this function directly, and
probably won't use invalid types anyway, the inferior diagnostic seems
acceptable.

libstdc++-v3/ChangeLog:

	* include/std/format (basic_format_parse_context::__once): New
	variable template.
	(basic_format_parse_context::__valid_types_for_check_dynamic_spec):
	New function template for checking argument types.
	(basic_format_parse_context::__check_dynamic_spec): New function
	template to implement the common check_dynamic_spec logic.
	(basic_format_parse_context::check_dynamic_spec_integral): Call
	__check_dynamic_spec instead of check_dynamic_spec.
	(basic_format_parse_context::check_dynamic_spec_string):
	Likewise. Use _CharT instead of char_type consistently.
	(basic_format_parse_context::check_dynamic_spec): Use
	__valid_types_for_check_dynamic_spec for precondition checks and
	call __check_dynamic_spec for checking the arg id.
	* testsuite/std/format/parse_ctx_neg.cc: Adjust expected errors.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>

0 files changed, 0 insertions, 0 deletions