* pt.c (tsubst_pack_expansion): Fix SFINAE.

From-SVN: r181548

gcc/cp/ChangeLog

 2011-11-20  Jason Merrill  <jason@redhat.com>
 
+	* pt.c (tsubst_pack_expansion): Fix SFINAE.
+
 	PR c++/48322
 	* cp-tree.h (PACK_EXPANSION_EXTRA_ARGS): New.
 	* cp-tree.def (EXPR_PACK_EXPANSION): Add an operand for it.

gcc/cp/pt.c

@@ -9350,7 +9350,9 @@ tsubst_pack_expansion (tree t, tree args, tsubst_flags_t complain,
 	    len = my_len;
           else if (len != my_len)
             {
-              if (TREE_CODE (t) == TYPE_PACK_EXPANSION)
+	      if (!(complain & tf_error))
+		/* Fail quietly.  */;
+              else if (TREE_CODE (t) == TYPE_PACK_EXPANSION)
                 error ("mismatched argument pack lengths while expanding "
                        "%<%T%>",
                        pattern);

gcc/testsuite/g++.dg/cpp0x/sfinae30.C

+// { dg-do compile { target c++11 } }
+
+template <class... T> struct tuple;
+template <class T> struct tuple<T> { T t; };
+
+template <class T, class U> struct pair;
+template<> struct pair<int,double> { };
+
+template <class... Ts>
+struct A
+{
+  template <class... Us,
+            class V = tuple<pair<Ts,Us>...> >
+  static void f(Us...)
+  {
+    V v;
+  }
+  template <class U>
+  static void f(bool);
+};
+
+int main()
+{
+  A<int,float>::f<double>(1.0);
+}