re PR c++/68965 (`-Wunused-parameter` is reported in variadic lambda or function…

re PR c++/68965 (`-Wunused-parameter` is reported in variadic lambda or function using sizeof...(xs))

	PR c++/68965
	* pt.c (tsubst_copy): Mark elements in expanded vector as used.

	* g++.dg/cpp1y/parameter-pack-1.C: New test.
	* g++.dg/cpp1y/parameter-pack-2.C: New test.

From-SVN: r232569

gcc/cp/ChangeLog

@@ -6,6 +6,9 @@
 	* cp-tree.h (clear_cv_cache, clear_fold_cache): Declare.
 	* decl.c (finish_enum_value_list): Call them.
 
+	PR c++/68965
+	* pt.c (tsubst_copy): Mark elements in expanded vector as used.
+
 2016-01-18  Patrick Palka  <ppalka@gcc.gnu.org>
 
 	PR c++/11858

gcc/cp/pt.c

@@ -14010,7 +14010,12 @@ tsubst_copy (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	  --c_inhibit_evaluation_warnings;
 
 	  if (TREE_CODE (expanded) == TREE_VEC)
+	    {
 	      len = TREE_VEC_LENGTH (expanded);
+	      /* Set TREE_USED for the benefit of -Wunused.  */
+	      for (int i = 0; i < len; i++)
+		TREE_USED (TREE_VEC_ELT (expanded, i)) = true;
+	    }
 
 	  if (expanded == error_mark_node)
 	    return error_mark_node;

gcc/testsuite/ChangeLog

+2016-01-19  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/68965
+	* g++.dg/cpp1y/parameter-pack-1.C: New test.
+	* g++.dg/cpp1y/parameter-pack-2.C: New test.
+
 2016-01-19  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	PR target/69135

gcc/testsuite/g++.dg/cpp1y/parameter-pack-1.C

+// PR c++/68965
+// { dg-do compile { target c++14 } }
+// { dg-options "-Wall -Wextra" }
+
+auto count = [](auto&&... xs)
+{
+    return sizeof...(xs);
+};
+
+struct count_struct
+{
+    template<typename... Ts>
+    auto operator()(Ts&&... xs)
+    {
+        return sizeof...(xs);
+    }
+};
+
+int main()
+{
+    count(1,2,3);
+    count_struct{}(1,2,3);
+}

gcc/testsuite/g++.dg/cpp1y/parameter-pack-2.C

+// PR c++/68965
+// { dg-do compile { target c++14 } }
+// { dg-options "-Wall -Wextra" }
+
+auto count = [](auto&&... xs) // { dg-warning "unused parameter" }
+{
+};
+
+struct count_struct
+{
+    template<typename... Ts>
+    auto operator()(Ts&&... xs) // { dg-warning "unused parameter" }
+    {
+    }
+};
+
+int main()
+{
+    count(1,2,3);
+    count_struct{}(1,2,3);
+}