https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112769
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:686b5eb9c9ee623a604dde5c49fa11c23f384c62 commit r14-8770-g686b5eb9c9ee623a604dde5c49fa11c23f384c62 Author: Patrick Palka <ppa...@redhat.com> Date: Fri Feb 2 19:07:08 2024 -0500 c++: requires-exprs and partial constraint subst [PR110006] In r11-3261-gb28b621ac67bee we made tsubst_requires_expr never partially substitute into a requires-expression so as to avoid checking its requirements out of order during e.g. generic lambda regeneration. These PRs however illustrate that we still sometimes do need to partially substitute into a requires-expression, in particular when it appears in associated constraints that we're directly substituting for sake of declaration matching or dguide constraint rewriting. In these cases we're being called from tsubst_constraint during which processing_constraint_expression_p is true, so this patch checks this predicate to control whether we defer substitution or partially substitute. In turn, we now need to propagate semantic tsubst flags through tsubst_requires_expr rather than just using tf_none, notably for sake of dguide constraint rewriting which sets tf_dguide. PR c++/110006 PR c++/112769 gcc/cp/ChangeLog: * constraint.cc (subst_info::quiet): Accomodate non-diagnostic tsubst flags. (tsubst_valid_expression_requirement): Likewise. (tsubst_simple_requirement): Return a substituted _REQ node when processing_template_decl. (tsubst_type_requirement_1): Accomodate non-diagnostic tsubst flags. (tsubst_type_requirement): Return a substituted _REQ node when processing_template_decl. (tsubst_compound_requirement): Likewise. Accomodate non-diagnostic tsubst flags. (tsubst_nested_requirement): Likewise. (tsubst_requires_expr): Don't defer partial substitution when processing_constraint_expression_p is true, in which case return a substituted REQUIRES_EXPR. * pt.cc (tsubst_expr) <case REQUIRES_EXPR>: Accomodate non-diagnostic tsubst flags. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/class-deduction-alias18.C: New test. * g++.dg/cpp2a/concepts-friend16.C: New test. Reviewed-by: Jason Merrill <ja...@redhat.com>
