PR c++/70844 - -Wuseless-cast and inheriting constructor.

	* method.c (forward_parm): Suppress warn_useless_cast.

From-SVN: r249344

gcc/cp/ChangeLog

+2017-06-17  Jason Merrill  <jason@redhat.com>
+
+	PR c++/70844 - -Wuseless-cast and inheriting constructor.
+	* method.c (forward_parm): Suppress warn_useless_cast.
+
 2017-06-16  Jason Merrill  <jason@redhat.com>
 
 	PR c++/81045 - Wrong type-dependence with auto return type.

gcc/cp/method.c

@@ -486,6 +486,7 @@ forward_parm (tree parm)
     type = PACK_EXPANSION_PATTERN (type);
   if (TREE_CODE (type) != REFERENCE_TYPE)
     type = cp_build_reference_type (type, /*rval=*/true);
+  warning_sentinel w (warn_useless_cast);
   exp = build_static_cast (type, exp, tf_warning_or_error);
   if (DECL_PACK_P (parm))
     exp = make_pack_expansion (exp);

gcc/testsuite/g++.dg/cpp0x/inh-ctor27.C

+// PR c++/70844
+// { dg-options -Wuseless-cast }
+// { dg-do compile { target c++11 } }
+
+struct base {
+    base (int const &);
+};
+
+struct derived : public base {
+    using base::base;
+};
+
+derived d(0);