re PR c++/40155 ([c++0x] variadic template pack problem)

Fix PR c++/40155

gcc/cp/ChangeLog:
	c++/40155
	* pt.c (unify_pack_expansion): In non-deduced contexts, re-use template
	arguments that were previously deduced.

gcc/testsuite/ChangeLog:
	c++/40155
	* g++.dg/cpp0x/variadic-unify-2.C: New test.

From-SVN: r155705

4 files changed, 32 insertions, 18 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 158e80d..07a3486 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2010-01-07  Dodji Seketeli  <dodji@redhat.com>
+
+	c++/40155
+	* pt.c (unify_pack_expansion): In non-deduced contexts, re-use template
+	arguments that were previously deduced.
+
 2010-01-05  Jason Merrill  <jason@redhat.com>
 
 	* pt.c (unify_pack_expansion): Handle deduction from init-list.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index d814736..f27b931 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -14074,8 +14074,15 @@ unify_pack_expansion (tree tparms, tree targs, tree packed_parms,
       tree old_pack = TREE_VALUE (pack);
       tree new_args = TREE_TYPE (pack);
       int i, len = TREE_VEC_LENGTH (new_args);
+      int idx, level;
       bool nondeduced_p = false;
 
+      /* By default keep the original deduced argument pack.
+	 If necessary, more specific code is going to update the
+	 resulting deduced argument later down in this function.  */
+      template_parm_level_and_index (TREE_PURPOSE (pack), &level, &idx);
+      TMPL_ARG (targs, level, idx) = old_pack;
+
       /* If NEW_ARGS contains any NULL_TREE entries, we didn't
 	 actually deduce anything.  */
       for (i = 0; i < len && !nondeduced_p; ++i)
@@ -14106,10 +14113,6 @@ unify_pack_expansion (tree tparms, tree targs, tree packed_parms,
       if (!old_pack)
         {
           tree result;
-          int idx, level;
-          
-          template_parm_level_and_index (TREE_PURPOSE (pack), &level, &idx);
-
           /* Build the deduced *_ARGUMENT_PACK.  */
           if (TREE_CODE (TREE_PURPOSE (pack)) == TEMPLATE_PARM_INDEX)
             {
@@ -14133,12 +14136,7 @@ unify_pack_expansion (tree tparms, tree targs, tree packed_parms,
         {
           /* We only had the explicitly-provided arguments before, but
              now we have a complete set of arguments.  */
-          int idx, level;
           tree explicit_args = ARGUMENT_PACK_EXPLICIT_ARGS (old_pack);
-          template_parm_level_and_index (TREE_PURPOSE (pack), &level, &idx);
-
-          /* Keep the original deduced argument pack.  */
-          TMPL_ARG (targs, level, idx) = old_pack;
 
           SET_ARGUMENT_PACK_ARGS (old_pack, new_args);
           ARGUMENT_PACK_INCOMPLETE_P (old_pack) = 1;
@@ -14148,15 +14146,6 @@ unify_pack_expansion (tree tparms, tree targs, tree packed_parms,
                                     new_args))
         /* Inconsistent unification of this parameter pack.  */
         return 1;
-      else
-        {
-          int idx, level;
-          
-          template_parm_level_and_index (TREE_PURPOSE (pack), &level, &idx);
-
-          /* Keep the original deduced argument pack.  */
-          TMPL_ARG (targs, level, idx) = old_pack;
-        }
     }
 
   return 0;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index d68e6e9..f222396 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2010-01-07  Dodji Seketeli  <dodji@redhat.com>
+
+	c++/40155
+	* g++.dg/cpp0x/variadic-unify-2.C: New test.
+
 2010-01-07  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/42625
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-unify-2.C b/gcc/testsuite/g++.dg/cpp0x/variadic-unify-2.C
new file mode 100644
index 0000000..80c9f5d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic-unify-2.C
@@ -0,0 +1,14 @@
+// Contributed by Dodji Seketeli <dodji@redhat.com>
+// Origin: PR c++/40155
+// { dg-options "-std=c++0x" }
+// { dg-do compile }
+
+template <typename T> struct identity
+{  typedef T type;  };
+
+template <typename RT, typename... A>
+int forward_call(RT (*) (A...), typename identity<A>::type...);
+
+int g (double);
+
+int i = forward_call(&g, 0);