[Bug c++/92049] bogus errors with -fchecking=2

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92049

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Caused by

@@ -26326,9 +26559,9 @@ build_non_dependent_expr (tree expr)
     unexpected recursive instantiations.  */
       && !parsing_nsdmi ()
       /* Don't do this during concept expansion either and for
-         the same reason.  */
-      && !expanding_concept ())
-    fold_non_dependent_expr (expr, tf_none);
+    the same reason.  */
+      && !parsing_constraint_expression_p ())
+    fold_non_dependent_expr (expr);

   STRIP_ANY_LOCATION_WRAPPER (expr);

found in

commit 5aadd5d943b0522963cb7afdb3484c45d867defb
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Jan 7 19:58:31 2019 -0500

    December checkpoint of C++2a Concepts overhaul.

    Squashed commit of the following:

but I don't see that change in the ChangeLog.  I guess we need that tf_none
back.  Testing a patch.