Revert "Remove code only needed to detect a pre-4.0 API break."

This reverts commit 17a3fbf2a3683f862de52e0058110eb8b356be56
due to build failures in llvm/unittests/ADT/IListTest.cpp

diff --git a/llvm/include/llvm/ADT/ilist.h b/llvm/include/llvm/ADT/ilist.h
index aed19cc..9913b7c 100644 (file)
--- a/llvm/include/llvm/ADT/ilist.h
+++ b/llvm/include/llvm/ADT/ilist.h
@@ -92,6 +92,63 @@ struct ilist_traits : public ilist_node_traits<NodeTy> {};
 /// Const traits should never be instantiated.
 template <typename Ty> struct ilist_traits<const Ty> {};
 
+namespace ilist_detail {
+
+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 {
+  typedef char Yes[1];
+  typedef char No[2];
+  template <size_t N> struct SFINAE {};
+
+  template <class U>
+  static Yes &test(U *I, decltype(I->getNext(&make<NodeT>())) * = nullptr);
+  template <class> static No &test(...);
+
+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 {
+  typedef char Yes[1];
+  typedef char No[2];
+
+  template <class U>
+  static Yes &test(U *I, decltype(I->createSentinel()) * = nullptr);
+  template <class> static No &test(...);
+
+public:
+  static const bool value = sizeof(test<TraitsT>(nullptr)) == sizeof(Yes);
+};
+
+/// Type trait to check for a traits class that has a createNode member.
+/// Allocation should be managed in a wrapper class, instead of in
+/// ilist_traits.
+template <class TraitsT, class NodeT> struct HasCreateNode {
+  typedef char Yes[1];
+  typedef char No[2];
+  template <size_t N> struct SFINAE {};
+
+  template <class U>
+  static Yes &test(U *I, decltype(I->createNode(make<NodeT>())) * = 0);
+  template <class> 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 = HasGetNext<TraitsT, NodeT>::value ||
+                            HasCreateSentinel<TraitsT>::value ||
+                            HasCreateNode<TraitsT, NodeT>::value;
+};
+
+} // end namespace ilist_detail
+
 //===----------------------------------------------------------------------===//
 //
 /// A wrapper around an intrusive list with callbacks and non-intrusive
@@ -125,6 +182,13 @@ public:
       typename base_list_type::const_reverse_iterator const_reverse_iterator;
 
 private:
+  // TODO: Drop this assertion and the transitive type traits anytime after
+  // v4.0 is branched (i.e,. keep them for one release to help out-of-tree code
+  // update).
+  static_assert(
+      !ilist_detail::HasObsoleteCustomization<TraitsT, value_type>::value,
+      "ilist customization points have changed!");
+
   static bool op_less(const_reference L, const_reference R) { return L < R; }
   static bool op_equal(const_reference L, const_reference R) { return L == R; }