... well, I suppose that in principle the super-safe thing to do in such
cases would be checking immediately and returning immediately only if we
are in a SFINAE context. Like in the untested patchlet attached.
Paolo.
/////////////////////
Index: pt.c
===================================================================
--- pt.c (revision 237196)
+++ pt.c (working copy)
@@ -13430,6 +13430,10 @@ tsubst (tree t, tree args, tsubst_flags_t complain
{
tree ctx = tsubst_aggr_type (TYPE_CONTEXT (t), args, complain,
in_decl, /*entering_scope=*/1);
+ if (!(complain & tf_error)
+ && ctx == error_mark_node)
+ return error_mark_node;
+
tree f = tsubst_copy (TYPENAME_TYPE_FULLNAME (t), args,
complain, in_decl);
