CWG 2233 - default arg and parameter pack

	* typeck.c (convert_arguments): Handle default arg followed by none.

From-SVN: r242350

gcc/cp/ChangeLog

 2016-11-12  Jason Merrill  <jason@redhat.com>
 
+	CWG 2233
+	* typeck.c (convert_arguments): Handle default arg followed by none.
+
 	* constexpr.c (potential_constant_expression_1): REALPART_EXPR and
 	IMAGPART_EXPR can be lvalues.
 

gcc/cp/typeck.c

@@ -3835,6 +3835,10 @@ convert_arguments (tree typelist, vec<tree, va_gc> **values, tree fndecl,
 	{
 	  for (; typetail != void_list_node; ++i)
 	    {
+	      /* After DR777, with explicit template args we can end up with a
+		 default argument followed by no default argument.  */
+	      if (!TREE_PURPOSE (typetail))
+		break;
 	      tree parmval
 		= convert_default_arg (TREE_VALUE (typetail),
 				       TREE_PURPOSE (typetail),
@@ -3850,9 +3854,10 @@ convert_arguments (tree typelist, vec<tree, va_gc> **values, tree fndecl,
 		break;
 	    }
 	}
-      else
+
+      if (typetail && typetail != void_list_node)
 	{
-          if (complain & tf_error)
+	  if (complain & tf_error)
 	    error_args_num (input_location, fndecl, /*too_many_p=*/false);
 	  return -1;
 	}

gcc/testsuite/g++.dg/cpp0x/variadic169.C

+// DR 2233
+// { dg-do compile { target c++11 } }
+
+template<typename ...T> void f(int n = 0, T ...t);
+
+int main()
+{
+  f<int>();			// { dg-error "too few arguments" }
+}