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diff --git a/antlr4-cpp-runtime-4.9.2-source/runtime/src/tree/ParseTreeVisitor.h b/antlr4-cpp-runtime-4.9.2-source/runtime/src/tree/ParseTreeVisitor.h
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+/* 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 "support/Any.h"
+
+namespace antlr4 {
+namespace tree {
+
+  /// <summary>
+  /// This interface defines the basic notion of a parse tree visitor. Generated
+  /// visitors implement this interface and the {@code XVisitor} interface for
+  /// grammar {@code X}.
+  /// </summary>
+  /// @param <T> The return type of the visit operation. Use <seealso cref="Void"/> for
+  /// operations with no return type. </param>
+  // ml: no template parameter here, to avoid the need for virtual template functions. Instead we have our Any class.
+  class ANTLR4CPP_PUBLIC ParseTreeVisitor {
+  public:
+    virtual ~ParseTreeVisitor();
+
+    /// <summary>
+    /// Visit a parse tree, and return a user-defined result of the operation.
+    /// </summary>
+    /// <param name="tree"> The <seealso cref="ParseTree"/> to visit. </param>
+    /// <returns> The result of visiting the parse tree. </returns>
+    virtual antlrcpp::Any visit(ParseTree *tree) = 0;
+
+    /// <summary>
+    /// Visit the children of a node, and return a user-defined result of the
+    /// operation.
+    /// </summary>
+    /// <param name="node"> The <seealso cref="ParseTree"/> whose children should be visited. </param>
+    /// <returns> The result of visiting the children of the node. </returns>
+    virtual antlrcpp::Any visitChildren(ParseTree *node) = 0;
+
+    /// <summary>
+    /// Visit a terminal node, and return a user-defined result of the operation.
+    /// </summary>
+    /// <param name="node"> The <seealso cref="TerminalNode"/> to visit. </param>
+    /// <returns> The result of visiting the node. </returns>
+    virtual antlrcpp::Any visitTerminal(TerminalNode *node) = 0;
+
+    /// <summary>
+    /// Visit an error node, and return a user-defined result of the operation.
+    /// </summary>
+    /// <param name="node"> The <seealso cref="ErrorNode"/> to visit. </param>
+    /// <returns> The result of visiting the node. </returns>
+    virtual antlrcpp::Any visitErrorNode(ErrorNode *node) = 0;
+
+  };
+
+} // namespace tree
+} // namespace antlr4