https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96097
--- Comment #9 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:25ac2bb57ae400621050a7e0845994336ca83b99 commit r15-3603-g25ac2bb57ae400621050a7e0845994336ca83b99 Author: Marek Polacek <pola...@redhat.com> Date: Tue Sep 3 17:01:48 2024 -0400 c++: ICE with TTP [PR96097] We crash when dependent_type_p gets a TEMPLATE_TYPE_PARM outside a template. That happens here because in template <template <typename T, typename T::type TT> typename X> void func() {} template <typename U, int I> struct Y {}; void g() { func<Y>(); } when performing overload resolution for func<Y>() we have to check if U matches T and I matches TT. So we wind up in coerce_template_template_parm/PARM_DECL. TREE_TYPE (arg) is int so we try to substitute TT's type, which is T::type. But we have nothing to substitute T with. And we call make_typename_type where ctx is still T, which checks dependent_scope_p and we trip the assert. It should work to always perform the substitution in a template context. If the result still contains template parameters, we cannot say if they match. PR c++/96097 gcc/cp/ChangeLog: * pt.cc (coerce_template_template_parm): Increment processing_template_decl before calling tsubst. gcc/testsuite/ChangeLog: * g++.dg/template/ttp44.C: New test.
