https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70229
--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
And the fix should be just to
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -419,7 +419,8 @@ check_constexpr_ctor_body_1 (tree last, tree list)
switch (TREE_CODE (list))
{
case DECL_EXPR:
- if (TREE_CODE (DECL_EXPR_DECL (list)) == USING_DECL)
+ if (TREE_CODE (DECL_EXPR_DECL (list)) == USING_DECL
+ || TREE_CODE (DECL_EXPR_DECL (list)) == TYPE_DECL)
return true;
return false;
but this is not a regression so I suppose we'll have to wait till gcc7?
