https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125490
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <[email protected]>: https://gcc.gnu.org/g:f7990da34872cfb448d4d1341714508904cb666c commit r17-1276-gf7990da34872cfb448d4d1341714508904cb666c Author: Patrick Palka <[email protected]> Date: Wed Jun 3 18:03:14 2026 -0400 c++: unchecked 'A op B' constraint-expression [PR125490] Here the nonsensical constraint-expression f() == 42 isn't getting rejected ahead of time because when parsing we pass no_toplevel_fold_p=true to cp_parser_binary_expression, which makes it use build_min instead of build_x_binary_op, effectively bypassing the actual processing of the operator expression until satisfaction time. This flag was introduced by r145014 to avoid undesirable folding / canonicalization of OpenMP for loop conditions, and that's still the only other user of the flag today. But I think cp_parser_constraint_expression doesn't need to use this flag at all because constraint-expression parsing is always templated and we (generally) don't fold templated trees. I think the flag is intended to be used only by OpenMP parsing routines. Note that without this patch we'd go on to reject the constraint-expression at satisfaction time, so this first testcase is effectively IFNDR / QoI. But this change isn't limited to IFNDR cases, we need to process the operator expression at parse time for sake of correct unqualified lookup as in the second testcase. PR c++/125490 gcc/cp/ChangeLog: * parser.cc (cp_parser_constraint_expression): Pass no_toplevel_fold_p=false instead of =true to cp_parser_binary_expression. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-pr125490.C: New test. * g++.dg/cpp2a/concepts-pr125490a.C: New test. Reviewed-by: Jason Merrill <[email protected]>
