From 0a5ec6afbe36caf8d7712dba36a4998d6cc8e2e4 Mon Sep 17 00:00:00 2001
From: asutton <asutton@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Fri, 20 Mar 2015 15:37:43 +0000
Subject: [PATCH] 2015-03-20  Andrew Sutton  <andrew.n.sutton@gmail.com>

	Ensure that empty expansions are satisfied.
	* gcc/cp/constraint.cc (check_pack_expansion): Empty expansions
	are satsified.
	* gcc/testsuite/g++.dg/concepts/template-parm11.C: New.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/c++-concepts@221536 138bc75d-0d04-0410-961f-82ee72b054a4
---
 ChangeLog.concepts                              |  7 +++++++
 gcc/cp/constraint.cc                            |  7 ++++++-
 gcc/testsuite/g++.dg/concepts/template-parm11.C | 20 ++++++++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/concepts/template-parm11.C

diff --git a/ChangeLog.concepts b/ChangeLog.concepts
index 76475b607c7..c1dc635926e 100644
--- a/ChangeLog.concepts
+++ b/ChangeLog.concepts
@@ -1,5 +1,12 @@
 2015-03-20  Andrew Sutton  <andrew.n.sutton@gmail.com>
 
+	Ensure that empty expansions are satisfied.
+	* gcc/cp/constraint.cc (check_pack_expansion): Empty expansions
+	are satsified.
+	* gcc/testsuite/g++.dg/concepts/template-parm11.C: New.
+
+2015-03-20  Andrew Sutton  <andrew.n.sutton@gmail.com>
+
 	Fix regression in variadic constraint processing.
 	* gcc/cp/pt.c (tsubst_pack_expansion): Expose declaration.
 	* gcc/cp/constraint.cc: Rename lift_constraints to
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 9e4e41f1ff8..f9b8ecee39c 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -1546,11 +1546,16 @@ check_pack_expansion (tree t, tree args,
   tree exprs = tsubst_pack_expansion (t, args, complain, in_decl);
   if (exprs == error_mark_node)
     return boolean_false_node;
+  int n = TREE_VEC_LENGTH (exprs);
+  
+  /* An empty expansion is inherently satisfied. */
+  if (n == 0)
+    return boolean_true_node;
 
   /* Build a conjunction of constraints from the resulting
      expansions and then check that. */
   tree result = NULL_TREE;
-  for (int i = 0; i < TREE_VEC_LENGTH (exprs); ++i)
+  for (int i = 0; i < n; ++i)
     {
       tree expr = TREE_VEC_ELT (exprs, i);
       tree constr = transform_expression (expr);
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm11.C b/gcc/testsuite/g++.dg/concepts/template-parm11.C
new file mode 100644
index 00000000000..c246850bf8f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/template-parm11.C
@@ -0,0 +1,20 @@
+// { dg-options "-std=c++1z" }
+
+template<typename T>
+concept bool NameProvider()
+{
+  return requires(){
+    T::_name_t::template _member_t<int>;
+  };
+}
+
+template<NameProvider... ColSpec>
+void getTable(const ColSpec&...)
+{}
+
+int f()
+{
+  getTable(7, 'a'); // { dg-error "cannot call" }
+};
+
+// { dg-excess-errors "ColSpec|false" }
-- 
2.11.4.GIT