openmp: Return error_mark_node from tsubst_attribute for errneous varidHEADtrunkmaster

We incorrectly accept some invalid declare variant cases as if declare
variant wasn't there, in particular if a function template has some dependent
arguments and variant name lookup fails, because that is during
fn_type_unification with complain=tf_none, it just sets it to error_mark_node
and doesn't complain further, because it doesn't know the substitution failed
(we don't return error_mark_node from tsubst_attribute, just create TREE_LIST
with error_mark_node TREE_PURPOSE).

The following patch fixes it by returning error_mark_node in that case, then
fn_type_unification caller can see it failed and can redo it with explain_p
so that errors are reported.

2024-11-01  Jakub Jelinek  <jakub@redhat.com>

	* pt.cc (tsubst_attribute): For "omp declare variant base" attribute
	if varid is error_mark_node, set val to error_mark_node rather than
	creating a TREE_LIST with error_mark_node TREE_PURPOSE.

	* g++.dg/gomp/declare-variant-10.C: New test.

0 files changed, 0 insertions, 0 deletions