From 7285637ab1390a21fb3da86ec73ac74e3550b32d Mon Sep 17 00:00:00 2001
From: jason <jason@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Fri, 16 Feb 2018 21:02:55 +0000
Subject: [PATCH] 	PR c++/81853 - using-directive and constexpr.

	* constexpr.c (cxx_eval_constant_expression): Handle USING_STMT.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@257762 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/cp/ChangeLog                      |  3 +++
 gcc/cp/constexpr.c                    |  4 ++++
 gcc/testsuite/g++.dg/ext/stmtexpr22.C | 13 +++++++++++++
 3 files changed, 20 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/stmtexpr22.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index b7d45707d5e..07788c0d516 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,8 @@
 2018-02-16  Jason Merrill  <jason@redhat.com>
 
+	PR c++/81853 - using-directive and constexpr.
+	* constexpr.c (cxx_eval_constant_expression): Handle USING_STMT.
+
 	PR c++/84420 - ICE with structured binding in lambda.
 	* lambda.c (is_capture_proxy): Check DECL_DECOMPOSITION_P.
 
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index d89bdd5a6a4..91148aa8d72 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -4726,6 +4726,10 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
 					jump_target);
       break;
 
+    case USING_STMT:
+      r = void_node;
+      break;
+
     default:
       if (STATEMENT_CODE_P (TREE_CODE (t)))
 	{
diff --git a/gcc/testsuite/g++.dg/ext/stmtexpr22.C b/gcc/testsuite/g++.dg/ext/stmtexpr22.C
new file mode 100644
index 00000000000..f46523a5875
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/stmtexpr22.C
@@ -0,0 +1,13 @@
+// PR c++/81853
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+namespace N {
+  enum { i };
+}
+
+int g ()
+{
+  constexpr int j = ({ using namespace N; i; });
+  return j;
+}
-- 
2.11.4.GIT