[clang] Optimize -Wunsafe-buffer-usage. (PR #124554)

[Ilya Biryukov via cfe-commits]

================
@@ -186,106 +205,202 @@ class MatchDescendantVisitor : public DynamicRecursiveASTVisitor {
     return DynamicRecursiveASTVisitor::TraverseStmt(Node);
   }
 
+  void set_ast_context(ASTContext &Context) { ActiveASTContext = &Context; }
+
+  void set_handler(const UnsafeBufferUsageHandler &NewHandler) {
+    Handler = &NewHandler;
+  }
+
 private:
   // Sets 'Matched' to true if 'Matcher' matches 'Node'
   //
   // Returns 'true' if traversal should continue after this function
   // returns, i.e. if no match is found or 'Bind' is 'BK_All'.
   template <typename T> bool match(const T &Node) {
-    internal::BoundNodesTreeBuilder RecursiveBuilder(*Builder);
-
-    if (Matcher->matches(DynTypedNode::create(Node), Finder,
-                         &RecursiveBuilder)) {
-      ResultBindings.addMatch(RecursiveBuilder);
+    if (Matcher->matches(DynTypedNode::create(Node), *ActiveASTContext,
+                         *Handler)) {
       Matches = true;
-      if (Bind != internal::ASTMatchFinder::BK_All)
+      if (!BindAll)
         return false; // Abort as soon as a match is found.
     }
     return true;
   }
 
-  const internal::DynTypedMatcher *const Matcher;
-  internal::ASTMatchFinder *const Finder;
-  internal::BoundNodesTreeBuilder *const Builder;
-  internal::BoundNodesTreeBuilder ResultBindings;
-  const internal::ASTMatchFinder::BindKind Bind;
+  CustomMatcher *const Matcher;
+  /// Defines how bindings are processed on recursive matches.
----------------
ilya-biryukov wrote:

NIT: `binding` is not really a concept we use anywhere else now that the matchers are gone.
Should this simply say "When false, finds the first match and stops. When true, finds all matches"?

https://github.com/llvm/llvm-project/pull/124554