https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118516
--- Comment #4 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:3605e057040ead00c072c20bfbb8f26636f8295e commit r15-7728-g3605e057040ead00c072c20bfbb8f26636f8295e Author: Marek Polacek <pola...@redhat.com> Date: Thu Feb 20 14:35:25 2025 -0500 c++: too many errors with sneaky template [PR118516] Since C++20 P0846, a name followed by a < can be treated as a template-name even though name lookup did not find a template-name. That happens in this test with "i < foo ()": for (int id = 0; i < foo(); ++id); and results in a raft of errors about non-constant foo(). The problem is that the require_potential_constant_expression call in cp_parser_template_argument emits errors even when we're parsing tentatively. So we repeat the error when we're trying to parse as a nested-name-specifier, type-name, etc. Guarding the call with !cp_parser_uncommitted_to_tentative_parse_p would mean that require_potential_constant_expression never gets called. But we don't need the call at all as far as I can tell. Stuff like template<int N> struct S { }; int foo () { return 4; } void g () { S<foo()> s; } gets diagnosed in convert_nontype_argument. In fact, with this patch, we only emit "call to non-constexpr function" once. (That is, in C++17 only; C++14 uses a different path.) PR c++/118516 gcc/cp/ChangeLog: * parser.cc (cp_parser_template_argument): Don't call require_potential_constant_expression. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/fn-template11.C: * g++.dg/template/fn-template1.C: New test. * g++.dg/template/fn-template2.C: New test.
