From 4200a7231e1ad67dc5476b7b6ab9ea015ccaa65d Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 11 Aug 2016 11:43:12 -0400
Subject: [PATCH] PR c++/73456 - ICE with constrained parameter pack.

	* logic.cc (non_atomic_constraint_p): Handle EXPR_PACK_EXPANSION.

From-SVN: r239376
---
 gcc/cp/ChangeLog                          |  5 +++++
 gcc/cp/logic.cc                           |  3 +++
 gcc/testsuite/g++.dg/concepts/variadic4.C | 20 ++++++++++++++++++++
 3 files changed, 28 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/concepts/variadic4.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 647b3e65800..04d6aa0ccbf 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2016-08-11  Jason Merrill  <jason@redhat.com>
+
+	PR c++/73456
+	* logic.cc (non_atomic_constraint_p): Handle EXPR_PACK_EXPANSION.
+
 2016-08-10  Jason Merrill  <jason@redhat.com>
 
 	Implement C++17 constexpr if.
diff --git a/gcc/cp/logic.cc b/gcc/cp/logic.cc
index dda98dfc310..b86e740e7c3 100644
--- a/gcc/cp/logic.cc
+++ b/gcc/cp/logic.cc
@@ -305,6 +305,9 @@ non_atomic_constraint_p (tree t)
     case ICONV_CONSTR:
     case DEDUCT_CONSTR:
     case EXCEPT_CONSTR:
+      /* A pack expansion isn't atomic, but it can't decompose to prove an
+	 atom, so it shouldn't cause analyze_atom to return undecided.  */
+    case EXPR_PACK_EXPANSION:
       return false;
     case CHECK_CONSTR:
     case PARM_CONSTR:
diff --git a/gcc/testsuite/g++.dg/concepts/variadic4.C b/gcc/testsuite/g++.dg/concepts/variadic4.C
new file mode 100644
index 00000000000..d20fa7da4e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/variadic4.C
@@ -0,0 +1,20 @@
+// PR c++/73456
+// { dg-options "-std=c++1z -fconcepts" }
+
+template<typename...> struct list {};
+
+template<typename Seq>
+concept bool Sequence = true;
+
+template<Sequence... Seqs>
+struct zip;
+
+template<Sequence... Seqs>
+    requires requires { typename list<Seqs...>; }
+// main.cpp:12:8: internal compiler error: in non_atomic_constraint_p, at cp/logic.cc:315
+struct zip<Seqs...> {};
+
+int main()
+{
+    zip<list<>, list<int>> {};
+}
-- 
2.30.2