ADT: Split ilist_node_traits into alloc and callback, NFC

Many lists want to override only allocation semantics, or callbacks for
iplist.  Split these up to prevent code duplication.
- Specialize ilist_alloc_traits to change the implementations of
  deleteNode() and createNode().
- One common desire is to do nothing deleteNode() and disable
  createNode().  Specialize ilist_alloc_traits to inherit from
  ilist_noalloc_traits for that behaviour.
- Specialize ilist_callback_traits to use the addNodeToList(),
  removeNodeFromList(), and transferNodesFromList() callbacks.

As a drive-by, add some coverage to the callback-related unit tests.

llvm-svn: 280128

1 files changed, 2 insertions, 9 deletions

diff --git a/llvm/lib/Support/YAMLParser.cpp b/llvm/lib/Support/YAMLParser.cpp
index 7490f1a9708..c083e1f1ebd 100644
--- a/llvm/lib/Support/YAMLParser.cpp
+++ b/llvm/lib/Support/YAMLParser.cpp
@@ -149,22 +149,15 @@ struct Token : ilist_node<Token> {
 }
 
 namespace llvm {
-template<>
-struct ilist_node_traits<Token> {
+template <> struct ilist_alloc_traits<Token> {
   Token *createNode(const Token &V) {
     return new (Alloc.Allocate<Token>()) Token(V);
   }
   static void deleteNode(Token *V) { V->~Token(); }
 
-  void addNodeToList(Token *) {}
-  void removeNodeFromList(Token *) {}
-  void transferNodesFromList(ilist_node_traits &    /*SrcTraits*/,
-                             ilist_iterator<Token> /*first*/,
-                             ilist_iterator<Token> /*last*/) {}
-
   BumpPtrAllocator Alloc;
 };
-}
+} // end namespace llvm
 
 typedef ilist<Token> TokenQueueT;