Re: C++ PATCH for c++/48322 (broken handling of variadic parms on multiple levels)

[Jason Merrill]

On 11/20/2011 07:22 PM, Jason Merrill wrote:

Hmm, actually, that still shouldn't have produced an error, it should
just SFINAE. Another bug to fix...

Thus.

Tested x86_64-pc-linux-gnu, applying to trunk.


commit 9c48487dc4ba1a0fd3235b03a00930379a8e7620
Author: Jason Merrill <ja...@redhat.com>
Date:   Sun Nov 20 19:33:21 2011 -0500

    	* pt.c (tsubst_pack_expansion): Fix SFINAE.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index f0ee0c5..2ba26b2 100644
--- a/gcc/cp/pt.c
+++ b/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);
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae30.C b/gcc/testsuite/g++.dg/cpp0x/sfinae30.C
new file mode 100644
index 0000000..6fcf5f7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae30.C
@@ -0,0 +1,25 @@
+// { 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);
+}