re PR c++/56177 (ICE when used forward for 'auto f();')

	PR c++/56177
	* decl.c (start_preparsed_function): Update restype if we change
	decl1.

From-SVN: r195780

gcc/cp/ChangeLog

 2013-02-05  Jason Merrill  <jason@redhat.com>
 
+	PR c++/56177
+	* decl.c (start_preparsed_function): Update restype if we change
+	decl1.
+
 	PR c++/56208
 	* pt.c (fn_type_unification): Discard any access checks from
 	substituting explicit args.

gcc/cp/decl.c

@@ -13116,6 +13116,7 @@ start_preparsed_function (tree decl1, tree attrs, int flags)
 	    DECL_CONTEXT (decl1) = DECL_CONTEXT (DECL_TI_TEMPLATE (decl1));
 	}
       fntype = TREE_TYPE (decl1);
+      restype = TREE_TYPE (fntype);
 
       /* If #pragma weak applies, mark the decl appropriately now.
 	 The pragma only applies to global functions.  Because

gcc/testsuite/g++.dg/cpp1y/auto-fn14.C

+// PR c++/56177
+// { dg-options "-std=c++1y" }
+
+auto f ();
+auto f () { return 33; }