https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93551
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jason Merrill <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:85409531ff032a008ebfbb715344648f15492dac commit r10-6438-g85409531ff032a008ebfbb715344648f15492dac Author: Jason Merrill <ja...@redhat.com> Date: Tue Feb 4 17:18:35 2020 -0500 c++: Fix error-recovery with concepts. Here, push_tinst_level refused to push into the scope of Foo::Foo because it was triggered from the ill-formed function fun. But we didn't check the return value and tried to pop the un-pushed level. PR c++/93551 * constraint.cc (satisfy_declaration_constraints): Check return value of push_tinst_level.