https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100372
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-11 branch has been updated by Jason Merrill <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:74ad5558d2acddcf4f5e96129ec29dd2f3d47d3a commit r11-8433-g74ad5558d2acddcf4f5e96129ec29dd2f3d47d3a Author: Jason Merrill <ja...@redhat.com> Date: Tue May 18 17:12:37 2021 -0400 c++: template template parm pack expansion [PR100372] Here we have a pack expansion of a template template parameter pack, of which the pattern is a TEMPLATE_DECL, which strip_typedefs doesn't want to see. PR c++/100372 gcc/cp/ChangeLog: * tree.c (strip_typedefs): Only look at the pattern of a TYPE_PACK_EXPANSION if it's a type. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/alias-decl-ttp1.C: New test.