https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100288
--- Comment #13 from CVS 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:c630157fd01140dbce120c1409c413a97dc17104 commit r13-6715-gc630157fd01140dbce120c1409c413a97dc17104 Author: Patrick Palka <ppa...@redhat.com> Date: Thu Mar 16 14:22:54 2023 -0400 c++: checking ICE with diagnosed constraint recursion [PR100288] When satisfaction_cache::get detects constraint recursion, it asserts that entry->result is empty. This makes sense when we're initially detecting/diagnosing recursion from the inner recursive call, but afterwards from the outer recursive call the recursion error is treated like any other unrelated constraint failure encountered during satisfaction, and we set entry->result to whatever the satisfaction value ended up being. Perhaps we should keep entry->result cleared in this case, but that'd require the inner recursive call to communicate to the outer recursive call that constraint recursion occurred, likely via setting entry->result to some sentinel value, which doesn't seem to be worth the complexity. So this patch just relaxes the problematic assert to accept non-empty entry->result as long as we've already issued an error. PR c++/100288 gcc/cp/ChangeLog: * constraint.cc (satisfaction_cache::get): Relax overly strict checking assert in the constraint recursion case. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-recursive-sat5.C: New test.
