re PR c++/68396 (function auto-deduced return types get incorrectly classified as parameter packs)

	PR c++/68396

2015-11-19  Ryan Burn  <contact@rnburn.com>

	* pt.c (find_parameter_packs_r) [DECLTYPE_TYPE]: When traversing
	the DECLTYPE_TYPE_EXPR, set type_pack_expansion_p to false.

From-SVN: r230620

gcc/cp/ChangeLog

+2015-11-19  Ryan Burn  <contact@rnburn.com>
+
+	PR c++/68396
+	* pt.c (find_parameter_packs_r) [DECLTYPE_TYPE]: When traversing
+	the DECLTYPE_TYPE_EXPR, set type_pack_expansion_p to false.
+
 2015-11-19  Cesar Philippidis  <cesar@codesourcery.com>
 
 	* parser.h (struct cp_omp_declare_simd_data): Add clauses member.

gcc/cp/pt.c

@@ -3551,6 +3551,20 @@ find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
       *walk_subtrees = 0;
       return NULL_TREE;
 
+    case DECLTYPE_TYPE:
+      {
+	/* When traversing a DECLTYPE_TYPE_EXPR, we need to set
+	   type_pack_expansion_p to false so that any placeholders
+	   within the expression don't get marked as parameter packs.  */
+	bool type_pack_expansion_p = ppd->type_pack_expansion_p;
+	ppd->type_pack_expansion_p = false;
+	cp_walk_tree (&DECLTYPE_TYPE_EXPR (t), &find_parameter_packs_r,
+		      ppd, ppd->visited);
+	ppd->type_pack_expansion_p = type_pack_expansion_p;
+	*walk_subtrees = 0;
+	return NULL_TREE;
+      }
+
     default:
       return NULL_TREE;
     }

gcc/testsuite/g++.dg/cpp1y/pr68396.C

+// { dg-do compile { target c++14 } }
+
+template <unsigned>
+auto f () {
+  return 2;
+}
+
+template <class>
+class A {};
+
+template <int... Ix>
+auto g () {
+  A<decltype(f<Ix> ())...>();
+  return f<2> ();
+}