https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96363
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-12 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:12d8a4a0fb26729290a184c40956329bb614625f commit r12-8600-g12d8a4a0fb26729290a184c40956329bb614625f Author: Patrick Palka <ppa...@redhat.com> Date: Thu May 26 09:43:14 2022 -0400 c++: constrained partial spec forward decl [PR96363] Here during cp_parser_single_declaration for #2, we were calling associate_classtype_constraints for TPL<T> (the primary template type) before maybe_process_partial_specialization could get a chance to notice that we're in fact declaring a distinct constrained partial spec and not redeclaring the primary template. This caused us to emit a bogus error about differing constraints b/t the primary template and #2's constraints. This patch fixes this by moving the call to associate_classtype_constraints after the call to shadow_tag (which calls maybe_process_partial_specialization) and adjusting shadow_tag to use the return value of m_p_p_s. Moreover, if we later try to define a constrained partial specialization that's been declared earlier (as in the third testcase), then maybe_new_partial_specialization correctly notices it's a redeclaration and returns NULL_TREE. But in this case we also need to update TYPE to point to the redeclared partial spec (it'll otherwise continue pointing to the primary template type, eventually leading to a bogus error). PR c++/96363 gcc/cp/ChangeLog: * decl.cc (shadow_tag): Use the return value of maybe_process_partial_specialization. * parser.cc (cp_parser_single_declaration): Call shadow_tag before associate_classtype_constraints. * pt.cc (maybe_new_partial_specialization): Change return type to bool. Take 'type' argument by mutable reference. Set 'type' to point to the correct constrained specialization when appropriate. (maybe_process_partial_specialization): Adjust accordingly. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-partial-spec12.C: New test. * g++.dg/cpp2a/concepts-partial-spec12a.C: New test. * g++.dg/cpp2a/concepts-partial-spec13.C: New test. (cherry picked from commit 97dc78d705a90c1ae83c78a7f2e24942cc3a6257)
