From 47265942fa55c8198ef712af8ee23c4700ca2dfb Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Mon, 25 Jul 2016 15:16:16 -0400
Subject: [PATCH] PR c++/71837 - pack expansion in init-capture

	* lambda.c (add_capture): Leave a pack expansion in a TREE_LIST.
	(build_lambda_object): Call build_x_compound_expr_from_list.
	* pt.c (tsubst) [DECLTYPE_TYPE]: Likewise.

From-SVN: r238733
---
 gcc/cp/ChangeLog                            |  5 +++++
 gcc/cp/lambda.c                             |  8 +++++++-
 gcc/cp/pt.c                                 | 12 ++++++++++++
 gcc/testsuite/g++.dg/cpp1y/lambda-init15.C  | 13 +++++++++++++
 gcc/testsuite/g++.dg/cpp1y/lambda-init15a.C | 14 ++++++++++++++
 5 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/lambda-init15.C
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/lambda-init15a.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 9ae7e67..8702097 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,10 @@
 2016-07-25  Jason Merrill  <jason@redhat.com>
 
+	PR c++/71837
+	* lambda.c (add_capture): Leave a pack expansion in a TREE_LIST.
+	(build_lambda_object): Call build_x_compound_expr_from_list.
+	* pt.c (tsubst) [DECLTYPE_TYPE]: Likewise.
+
 	PR c++/71833
 	PR c++/54440
 	* pt.c (coerce_template_parameter_pack): Fix logic for
diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c
index 4d6d80f..9bf8a56 100644
--- a/gcc/cp/lambda.c
+++ b/gcc/cp/lambda.c
@@ -79,6 +79,10 @@ build_lambda_object (tree lambda_expr)
 	  goto out;
 	}
 
+      if (TREE_CODE (val) == TREE_LIST)
+	val = build_x_compound_expr_from_list (val, ELK_INIT,
+					       tf_warning_or_error);
+
       if (DECL_P (val))
 	mark_used (val);
 
@@ -449,7 +453,9 @@ add_capture (tree lambda, tree id, tree orig_init, bool by_reference_p,
       variadic = true;
     }
 
-  if (TREE_CODE (initializer) == TREE_LIST)
+  if (TREE_CODE (initializer) == TREE_LIST
+      /* A pack expansion might end up with multiple elements.  */
+      && !PACK_EXPANSION_P (TREE_VALUE (initializer)))
     initializer = build_x_compound_expr_from_list (initializer, ELK_INIT,
 						   tf_warning_or_error);
   type = TREE_TYPE (initializer);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 7dd6b25..97d5000 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -13620,6 +13620,18 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 				      /*function_p*/false,
 				      /*integral_constant_expression*/false);
 
+	if (DECLTYPE_FOR_INIT_CAPTURE (t))
+	  {
+	    if (type == NULL_TREE)
+	      {
+		if (complain & tf_error)
+		  error ("empty initializer in lambda init-capture");
+		type = error_mark_node;
+	      }
+	    else if (TREE_CODE (type) == TREE_LIST)
+	      type = build_x_compound_expr_from_list (type, ELK_INIT, complain);
+	  }
+
 	--cp_unevaluated_operand;
 	--c_inhibit_evaluation_warnings;
 
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-init15.C b/gcc/testsuite/g++.dg/cpp1y/lambda-init15.C
new file mode 100644
index 0000000..8b3e520
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/lambda-init15.C
@@ -0,0 +1,13 @@
+// PR c++/71837
+// { dg-do compile { target c++14 } }
+
+template < typename ... Ts > void f (Ts ... args)
+{
+  [ts (args ...)] { return ts; } ();
+}
+
+int main ()
+{ 
+  f (0);
+  return 0;
+}
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-init15a.C b/gcc/testsuite/g++.dg/cpp1y/lambda-init15a.C
new file mode 100644
index 0000000..166d650
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/lambda-init15a.C
@@ -0,0 +1,14 @@
+// PR c++/71837
+// { dg-do compile { target c++14 } }
+
+template < typename ... Ts > void f (Ts ... args)
+{
+  [ts (args ...)] { return ts; } (); // { dg-error "" }
+}
+
+int main ()
+{ 
+  f ();				// { dg-message "required" }
+  f (1,2);			// { dg-message "required" }
+  return 0;
+}
-- 
2.7.4