https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107126
--- Comment #9 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:cff174fabd6c980c09aee95db1d9d5c22421761f commit r14-8915-gcff174fabd6c980c09aee95db1d9d5c22421761f Author: Marek Polacek <pola...@redhat.com> Date: Fri Feb 2 14:53:01 2024 -0500 c++: DR2237, cdtor and template-id tweaks [PR107126] Since my r11-532 changes to implement DR2237, for this test: template<typename T> struct S { S<T>(); }; in C++20 we emit the ugly: q.C:3:8: error: expected unqualified-id before ')' token 3 | S<T>(); which doesn't explain what the problem is. This patch improves that diagnostic, reduces the error to a pedwarn, and adds a -Wc++20-compat diagnostic. We now say: q.C:3:7: warning: template-id not allowed for constructor in C++20 [-Wtemplate-id-cdtor] 3 | S<T>(); q.C:3:7: note: remove the '< >' This patch also fixes <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97202#c8> where the C++20 diagnostic was missing altogether: The problem was that I checked for CPP_TEMPLATE_ID too early, at a point at which cp_parser_template_id may not have been called yet. So let's check for it at the end of the function, after the tentative parse and rollback. -Wc++20-compat triggered in libitm/; I sent a patch for that. DR 2237 PR c++/107126 PR c++/97202 gcc/c-family/ChangeLog: * c-opts.cc (c_common_post_options): In C++20 or with -Wc++20-compat, turn on -Wtemplate-id-cdtor. * c.opt (Wtemplate-id-cdtor): New. gcc/cp/ChangeLog: * parser.cc (cp_parser_unqualified_id): Downgrade the DR2237 error to a pedwarn. (cp_parser_constructor_declarator_p): Likewise. gcc/ChangeLog: * doc/invoke.texi: Document -Wtemplate-id-cdtor. gcc/testsuite/ChangeLog: * g++.dg/DRs/dr2237.C: Adjust dg-error. * g++.dg/parse/constructor2.C: Likewise. * g++.dg/template/error34.C: Likewise. * g++.old-deja/g++.pt/ctor2.C: Likewise. * g++.dg/DRs/dr2237-2.C: New test. * g++.dg/DRs/dr2237-3.C: New test. * g++.dg/DRs/dr2237-4.C: New test. * g++.dg/DRs/dr2237-5.C: New test. * g++.dg/warn/Wtemplate-id-cdtor-1.C: New test. * g++.dg/warn/Wtemplate-id-cdtor-2.C: New test. * g++.dg/warn/Wtemplate-id-cdtor-3.C: New test. * g++.dg/warn/Wtemplate-id-cdtor-4.C: New test.
