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diff --git a/deps/v8/third_party/antlr4/runtime/Cpp/runtime/src/tree/AbstractParseTreeVisitor.h b/deps/v8/third_party/antlr4/runtime/Cpp/runtime/src/tree/AbstractParseTreeVisitor.h
new file mode 100644
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+++ b/deps/v8/third_party/antlr4/runtime/Cpp/runtime/src/tree/AbstractParseTreeVisitor.h
@@ -0,0 +1,127 @@
+/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+
+#pragma once
+
+#include "tree/ParseTreeVisitor.h"
+
+namespace antlr4 {
+namespace tree {
+
+class ANTLR4CPP_PUBLIC AbstractParseTreeVisitor : public ParseTreeVisitor {
+ public:
+  /// The default implementation calls <seealso cref="ParseTree#accept"/> on the
+  /// specified tree.
+  virtual antlrcpp::Any visit(ParseTree* tree) override {
+    return tree->accept(this);
+  }
+
+  /**
+   * <p>The default implementation initializes the aggregate result to
+   * {@link #defaultResult defaultResult()}. Before visiting each child, it
+   * calls {@link #shouldVisitNextChild shouldVisitNextChild}; if the result
+   * is {@code false} no more children are visited and the current aggregate
+   * result is returned. After visiting a child, the aggregate result is
+   * updated by calling {@link #aggregateResult aggregateResult} with the
+   * previous aggregate result and the result of visiting the child.</p>
+   *
+   * <p>The default implementation is not safe for use in visitors that modify
+   * the tree structure. Visitors that modify the tree should override this
+   * method to behave properly in respect to the specific algorithm in use.</p>
+   */
+  virtual antlrcpp::Any visitChildren(ParseTree* node) override {
+    antlrcpp::Any result = defaultResult();
+    size_t n = node->children.size();
+    for (size_t i = 0; i < n; i++) {
+      if (!shouldVisitNextChild(node, result)) {
+        break;
+      }
+
+      antlrcpp::Any childResult = node->children[i]->accept(this);
+      result = aggregateResult(result, childResult);
+    }
+
+    return result;
+  }
+
+  /// The default implementation returns the result of
+  /// <seealso cref="#defaultResult defaultResult"/>.
+  virtual antlrcpp::Any visitTerminal(TerminalNode* /*node*/) override {
+    return defaultResult();
+  }
+
+  /// The default implementation returns the result of
+  /// <seealso cref="#defaultResult defaultResult"/>.
+  virtual antlrcpp::Any visitErrorNode(ErrorNode* /*node*/) override {
+    return defaultResult();
+  }
+
+ protected:
+  /// <summary>
+  /// Gets the default value returned by visitor methods. This value is
+  /// returned by the default implementations of
+  /// <seealso cref="#visitTerminal visitTerminal"/>, <seealso
+  /// cref="#visitErrorNode visitErrorNode"/>. The default implementation of
+  /// <seealso cref="#visitChildren visitChildren"/> initializes its aggregate
+  /// result to this value. <p/> The base implementation returns {@code null}.
+  /// </summary>
+  /// <returns> The default value returned by visitor methods. </returns>
+  virtual antlrcpp::Any defaultResult() {
+    return nullptr;  // support isNotNull
+  }
+
+  /// <summary>
+  /// Aggregates the results of visiting multiple children of a node. After
+  /// either all children are visited or <seealso cref="#shouldVisitNextChild"/>
+  /// returns
+  /// {@code false}, the aggregate value is returned as the result of
+  /// <seealso cref="#visitChildren"/>.
+  /// <p/>
+  /// The default implementation returns {@code nextResult}, meaning
+  /// <seealso cref="#visitChildren"/> will return the result of the last child
+  /// visited (or return the initial value if the node has no children).
+  /// </summary>
+  /// <param name="aggregate"> The previous aggregate value. In the default
+  /// implementation, the aggregate value is initialized to
+  /// <seealso cref="#defaultResult"/>, which is passed as the {@code aggregate}
+  /// argument to this method after the first child node is visited. </param>
+  /// <param name="nextResult"> The result of the immediately preceeding call to
+  /// visit a child node.
+  /// </param>
+  /// <returns> The updated aggregate result. </returns>
+  virtual antlrcpp::Any aggregateResult(antlrcpp::Any /*aggregate*/,
+                                        const antlrcpp::Any& nextResult) {
+    return nextResult;
+  }
+
+  /// <summary>
+  /// This method is called after visiting each child in
+  /// <seealso cref="#visitChildren"/>. This method is first called before the
+  /// first child is visited; at that point {@code currentResult} will be the
+  /// initial value (in the default implementation, the initial value is
+  /// returned by a call to <seealso cref="#defaultResult"/>. This method is not
+  /// called after the last child is visited. <p/> The default implementation
+  /// always returns {@code true}, indicating that
+  /// {@code visitChildren} should only return after all children are visited.
+  /// One reason to override this method is to provide a "short circuit"
+  /// evaluation option for situations where the result of visiting a single
+  /// child has the potential to determine the result of the visit operation as
+  /// a whole.
+  /// </summary>
+  /// <param name="node"> The <seealso cref="ParseTree"/> whose children are
+  /// currently being visited. </param> <param name="currentResult"> The current
+  /// aggregate result of the children visited to the current point.
+  /// </param>
+  /// <returns> {@code true} to continue visiting children. Otherwise return
+  /// {@code false} to stop visiting children and immediately return the
+  /// current aggregate result from <seealso cref="#visitChildren"/>. </returns>
+  virtual bool shouldVisitNextChild(ParseTree* /*node*/,
+                                    const antlrcpp::Any& /*currentResult*/) {
+    return true;
+  }
+};
+
+}  // namespace tree
+}  // namespace antlr4