https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119378
--- Comment #6 from GCC 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:05ea8baf6ff96c77a9a2467d5c45b1ed575fca92 commit r16-309-g05ea8baf6ff96c77a9a2467d5c45b1ed575fca92 Author: Patrick Palka <ppa...@redhat.com> Date: Wed Apr 30 10:54:23 2025 -0400 c++: UNBOUND_CLASS_TEMPLATE context substitution [PR119981] In r15-123 and r14-11434 we unconditionally set processing_template_decl when substituting the context of an UNBOUND_CLASS_TEMPLATE, in order to handle instantiation of the dependently scoped friend declaration template<int N> template<class T> friend class A<N>::B; where the scope A<N> remains dependent after instantiation. But this turns out to misbehave for the UNBOUND_CLASS_TEMPLATE in the below testcase representing g<[]{}>::template fn since with the flag set substituting the args of test3 into the lambda causes us to defer the substitution and yield a lambda that still looks dependent, which in turn makes g<[]{}> still dependent and not suitable for qualified name lookup. This patch restricts setting processing_template_decl during UNBOUND_CLASS_TEMPLATE substitution to the case where there are multiple levels of introduced template parameters, as in the friend declaration. (This means we need to substitute the template parameter list(s) first, which makes sense since they lexically appear first.) PR c++/119981 PR c++/119378 gcc/cp/ChangeLog: * pt.cc (tsubst) <case UNBOUND_CLASS_TEMPLATE>: Substitute into template parameter list first. When substituting the context, only set processing_template_decl if there's more than one level of introduced template parameters. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/lambda-targ15.C: New test. Reviewed-by: Jason Merrill <ja...@redhat.com>
