https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105982
--- Comment #3 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:01aff2ba18a654324957af446a3065db489c0f14 commit r13-1224-g01aff2ba18a654324957af446a3065db489c0f14 Author: Patrick Palka <ppa...@redhat.com> Date: Thu Jun 23 16:18:55 2022 -0400 c++: context completion in lookup_template_class [PR105982] The below testcase demonstrates that completion of the substituted context during lookup_template_class can end up registering the desired specialization for us in more cases than r13-1045-gcb7fd1ea85feea anticipated. In particular this can happen for a non-dependent specialization of a nested class as well. For this testcase, during overload resolution with A's guides, we substitute the deduced argument T=int into the TYPENAME_TYPE B::C, during which we call lookup_template_class for A<T>::B with T=int, which completes A<int> for the first time, which recursively registers the desired specialization of B already. The parent call to lookup_template_class then tries to register the same specialization, triggering an ICE. This patch fixes this by making lookup_template_class determine more directly whether we need to recheck the specializations table after completion of the context -- when and only when the call to complete_type had an effect. PR c++/105982 gcc/cp/ChangeLog: * pt.cc (lookup_template_class): After calling complete_type for the substituted context, check the table again iff the type was previously incomplete and complete_type made it complete. gcc/testsuite/ChangeLog: * g++.dg/cpp1z/class-deduction111.C: New test.
