From 762c7604e5515a429002431bc4b29dbe0405c7b3 Mon Sep 17 00:00:00 2001
From: "Duncan P. N. Exon Smith" <dexonsmith@apple.com>
Date: Wed, 17 Aug 2016 23:47:56 +0000
Subject: [PATCH] ADT: Tidy up ilist_traits static asserts, NFC

Change the ilist traits to use decltype instead of sizeof, and add
HasObsoleteCustomization so that additions to this list don't need to be
added in two places.

I suspect this will now work with MSVC, since the trait tested in
r278991 seems to work.  If for some reason it continues to fail on
Windows I'll follow up by adding back the #ifndef _MSC_VER.

llvm-svn: 279012
---
 include/llvm/ADT/ilist.h    | 35 ++++++++++++++++-------------------
 unittests/ADT/ilistTest.cpp | 17 +++++++++++++++++
 2 files changed, 33 insertions(+), 19 deletions(-)

diff --git a/include/llvm/ADT/ilist.h b/include/llvm/ADT/ilist.h
index 10ff088dcd6..c77730c99a3 100644
--- a/include/llvm/ADT/ilist.h
+++ b/include/llvm/ADT/ilist.h
@@ -83,34 +83,37 @@ template <class T> T &make();
 
 /// Type trait to check for a traits class that has a getNext member (as a
 /// canary for any of the ilist_nextprev_traits API).
-template <class TraitsT, class NodeT> struct HasGetNext {
+template <class TraitsT, class NodeT> class HasGetNext {
   typedef char Yes[1];
   typedef char No[2];
   template <size_t N> struct SFINAE {};
 
   template <class U>
-  static Yes &hasGetNext(
-      SFINAE<sizeof(static_cast<NodeT *>(make<U>().getNext(&make<NodeT>())))>
-          * = 0);
-  template <class U> static No &hasGetNext(...);
+  static Yes &test(U *I, decltype(I->getNext(&make<NodeT>())) * = 0);
+  template <class> static No &test(...);
 
-  static const bool value = sizeof(hasGetNext<TraitsT>(nullptr)) == sizeof(Yes);
+public:
+  static const bool value = sizeof(test<TraitsT>(nullptr)) == sizeof(Yes);
 };
 
 /// Type trait to check for a traits class that has a createSentinel member (as
 /// a canary for any of the ilist_sentinel_traits API).
-template <class TraitsT> struct HasCreateSentinel {
+template <class TraitsT> class HasCreateSentinel {
   typedef char Yes[1];
   typedef char No[2];
   template <size_t N> struct SFINAE {};
 
   template <class U>
-  static Yes &
-  hasCreateSentinel(SFINAE<sizeof(make<U>().createSentinel())> * = 0);
-  template <class U> static No &hasCreateSentinel(...);
+  static Yes &test(U *I, decltype(I->createSentinel()) * = 0);
+  template <class U> static No &test(...);
 
+public:
+  static const bool value = sizeof(test<TraitsT>(nullptr)) == sizeof(Yes);
+};
+
+template <class TraitsT, class NodeT> struct HasObsoleteCustomization {
   static const bool value =
-      sizeof(hasCreateSentinel<TraitsT>(nullptr)) == sizeof(Yes);
+      HasGetNext<TraitsT, NodeT>::value || HasCreateSentinel<TraitsT>::value;
 };
 
 } // end namespace ilist_detail
@@ -287,14 +290,8 @@ template <typename NodeTy, typename Traits = ilist_traits<NodeTy>>
 class iplist : public Traits, ilist_node_access {
   // TODO: Drop these assertions anytime after 4.0 is branched (keep them for
   // one release to help out-of-tree code update).
-#if !defined(_MSC_VER)
-  // FIXME: This fails in MSVC, but it's worth keeping around to help
-  // non-Windows users root out bugs in their ilist_traits.
-  static_assert(!ilist_detail::HasGetNext<Traits, NodeTy>::value,
-                "ilist next and prev links are not customizable!");
-  static_assert(!ilist_detail::HasCreateSentinel<Traits>::value,
-                "ilist sentinel is not customizable!");
-#endif
+  static_assert(!ilist_detail::HasObsoleteCustomization<Traits, NodeTy>::value,
+                "ilist customization points have changed!");
 
   ilist_sentinel<NodeTy> Sentinel;
 
diff --git a/unittests/ADT/ilistTest.cpp b/unittests/ADT/ilistTest.cpp
index a8ea63ed464..57cdd584ec1 100644
--- a/unittests/ADT/ilistTest.cpp
+++ b/unittests/ADT/ilistTest.cpp
@@ -190,4 +190,21 @@ TEST(ilistTest, privateNode) {
   L2.remove(&N);
 }
 
+struct GetNext {
+  Node *getNext(Node *);
+};
+TEST(ilistTest, HasGetNextTrait) {
+  EXPECT_TRUE((ilist_detail::HasGetNext<GetNext, Node>::value));
+  EXPECT_TRUE((ilist_detail::HasObsoleteCustomization<GetNext, Node>::value));
+}
+
+struct CreateSentinel {
+  Node *createSentinel();
+};
+TEST(ilistTest, HasCreateSentinel) {
+  EXPECT_TRUE((ilist_detail::HasCreateSentinel<CreateSentinel>::value));
+  EXPECT_TRUE(
+      (ilist_detail::HasObsoleteCustomization<CreateSentinel, Node>::value));
+}
+
 } // end namespace