https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95468
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-9 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:1b265d910f27743dc3ea8e4fde6c292df220fb9f commit r9-9456-g1b265d910f27743dc3ea8e4fde6c292df220fb9f Author: Patrick Palka <ppa...@redhat.com> Date: Tue Feb 23 09:40:09 2021 -0500 c++: Fix folding of non-dependent BASELINKs [PR95468] Here, the problem ultimately seems to be that tsubst_copy_and_build, when called with empty args as we do during non-dependent expression folding, doesn't touch BASELINKs at all: it delegates to tsubst_copy which then immediately exits early due to the empty args. This means that the CAST_EXPR int(1) in the BASELINK A::condition<int(1)> never gets folded (as part of folding of the overall CALL_EXPR), which later causes us to crash when performing overload resolution of the rebuilt CALL_EXPR (which is still in terms of this templated BASELINK). This doesn't happen when condition() is a namespace-scope function because then condition<int(1)> is represented by a TEMPLATE_ID_EXPR rather than by a BASELINK, which does get handled directly from tsubst_copy_and_build. This patch fixes this issue by having tsubst_copy_and_build handle BASELINK directly rather than delegating to tsubst_copy, so that it processes BASELINKs even when args is empty. gcc/cp/ChangeLog: PR c++/95468 * pt.c (tsubst_copy_and_build) <case BASELINK>: New case, copied over from tsubst_copy. gcc/testsuite/ChangeLog: PR c++/95468 * g++.dg/template/non-dependent15.C: New test. (cherry picked from commit 5bd7afb71fca3a5a6e9f8586d86903bae1849193)
