A non-type template parm with a placeholder type is type-dependent.

	* pt.c (type_dependent_expression_p): A non-type template parm with
	a placeholder type is type-dependent.

From-SVN: r270984

gcc/cp/ChangeLog

+2019-05-07  Jason Merrill  <jason@redhat.com>
+
+	* pt.c (type_dependent_expression_p): A non-type template parm with
+	a placeholder type is type-dependent.
+
 2019-05-06  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/90265 - ICE with generic lambda.

gcc/cp/pt.c

@@ -25981,6 +25981,13 @@ type_dependent_expression_p (tree expression)
       return false;
     }
 
+  /* The type of a non-type template parm declared with a placeholder type
+     depends on the corresponding template argument, even though
+     placeholders are not normally considered dependent.  */
+  if (TREE_CODE (expression) == TEMPLATE_PARM_INDEX
+      && is_auto (TREE_TYPE (expression)))
+    return true;
+
   gcc_assert (TREE_CODE (expression) != TYPE_DECL);
 
   /* Dependent type attributes might not have made it from the decl to