Use satisfaction with nested requirements.

Use satisfaction with nested requirements.

gcc/cp/

2019-11-06  Andrew Sutton  <asutton@lock3software.com>

	* constraint.cc (build_parameter_mapping): Use
	current_template_parms when the declaration is not available.
	(norm_info::norm_info) Make explicit.
	(normalize_constraint_expression): Factor into a separate overload
	that takes arguments, and use that in the original function.
	(tsubst_nested_requirement): Use satisfy_constraint instead of
	trying to evaluate this as a constant expression.
	(finish_nested_requirement): Keep the normalized constraint and the
	original normalization arguments with the requirement.
	(diagnose_nested_requirement): Use satisfy_constraint. Tentatively
	implement more comprehensive diagnostics, but do not enable.
	* parser.c (cp_parser_requires_expression): Relax requirement that
	requires-expressions can live only inside templates.
	* pt.c (any_template_parm_r): Look into type of PARM_DECL.

2019-11-06  Jason Merrill  <jason@redhat.com>

	* pt.c (use_pack_expansion_extra_args_p): Still do substitution if
	all packs are simple pack expansions.
	(add_extra_args): Check that the extra args aren't dependent.

gcc/testsuite/
	* lib/prune.exp: Ignore "in requirements" in diagnostics.
	* g++.dg/cpp2a/requires-18.C: New test.
	* g++.dg/cpp2a/requires-19.C: New test.

From-SVN: r277900