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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.
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/*
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   John Lenz
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package com.google.javascript.rhino;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.javascript.jscomp.base.JSCompDoubles.isPositive;

import com.google.common.base.Preconditions;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.List;

/**
 * An AST construction helper class
 *
 * @author [email protected] (John Lenz)
 */
public class IR {

  private IR() {}

  public static Node empty() {
    return new Node(Token.EMPTY);
  }

  public static Node export(Node declaration) {
    return new Node(Token.EXPORT, declaration);
  }

  public static Node importNode(Node name, Node importSpecs, Node moduleIdentifier) {
    checkState(name.isName() || name.isEmpty(), name);
    checkState(
        importSpecs.isImportSpec() || importSpecs.isImportStar() || importSpecs.isEmpty(),
        importSpecs);
    checkState(moduleIdentifier.isStringLit(), moduleIdentifier);
    return new Node(Token.IMPORT, name, importSpecs, moduleIdentifier);
  }

  public static Node importStar(String name) {
    return Node.newString(Token.IMPORT_STAR, name);
  }

  public static Node function(Node name, Node params, Node body) {
    checkState(name.isName());
    checkState(params.isParamList());
    checkState(body.isBlock());
    return new Node(Token.FUNCTION, name, params, body);
  }

  public static Node arrowFunction(Node name, Node params, Node body) {
    checkState(name.isName());
    checkState(params.isParamList());
    checkState(body.isBlock() || mayBeExpression(body));
    Node func = new Node(Token.FUNCTION, name, params, body);
    func.setIsArrowFunction(true);
    return func;
  }

  public static Node paramList(Node... params) {
    Node paramList = new Node(Token.PARAM_LIST);
    for (Node param : params) {
      checkState(param.isName() || param.isRest() || param.isDefaultValue());
      paramList.addChildToBack(param);
    }
    return paramList;
  }

  public static Node root(Node... rootChildren) {
    Node root = new Node(Token.ROOT);
    for (Node child : rootChildren) {
      checkState(child.getToken() == Token.ROOT || child.getToken() == Token.SCRIPT);
      root.addChildToBack(child);
    }
    return root;
  }

  public static Node block() {
    Node block = new Node(Token.BLOCK);
    return block;
  }

  public static Node block(Node stmt) {
    checkState(mayBeStatement(stmt), "Block node cannot contain %s", stmt.getToken());
    Node block = new Node(Token.BLOCK, stmt);
    return block;
  }

  public static Node block(Node... stmts) {
    Node block = block();
    for (Node stmt : stmts) {
      checkState(mayBeStatement(stmt));
      block.addChildToBack(stmt);
    }
    return block;
  }

  public static Node block(List stmts) {
    Node paramList = block();
    for (Node stmt : stmts) {
      checkState(mayBeStatement(stmt));
      paramList.addChildToBack(stmt);
    }
    return paramList;
  }

  private static Node blockUnchecked(Node stmt) {
    return new Node(Token.BLOCK, stmt);
  }

  public static Node script() {
    // TODO(johnlenz): finish setting up the SCRIPT node
    Node block = new Node(Token.SCRIPT);
    return block;
  }

  public static Node script(Node... stmts) {
    Node block = script();
    for (Node stmt : stmts) {
      checkState(mayBeStatementNoReturn(stmt));
      block.addChildToBack(stmt);
    }
    return block;
  }

  public static Node script(List stmts) {
    Node paramList = script();
    for (Node stmt : stmts) {
      checkState(mayBeStatementNoReturn(stmt));
      paramList.addChildToBack(stmt);
    }
    return paramList;
  }

  public static Node var(Node lhs, Node value) {
    return declaration(lhs, value, Token.VAR);
  }

  public static Node var(Node lhs) {
    return declaration(lhs, Token.VAR);
  }

  public static Node let(Node lhs, Node value) {
    return declaration(lhs, value, Token.LET);
  }

  public static Node let(Node lhs) {
    return declaration(lhs, Token.LET);
  }

  public static Node constNode(Node lhs, Node value) {
    return declaration(lhs, value, Token.CONST);
  }

  public static Node declaration(Node lhs, Token type) {
    checkState(lhs.isName() || lhs.isDestructuringPattern() || lhs.isDestructuringLhs(), lhs);
    if (lhs.isDestructuringPattern()) {
      lhs = new Node(Token.DESTRUCTURING_LHS, lhs);
    }
    return new Node(type, lhs);
  }

  public static Node declaration(Node lhs, Node value, Token type) {
    if (lhs.isName()) {
      checkState(!lhs.hasChildren());
    } else {
      checkState(lhs.isArrayPattern() || lhs.isObjectPattern());
      lhs = new Node(Token.DESTRUCTURING_LHS, lhs);
    }
    Preconditions.checkState(mayBeExpression(value), "%s can't be an expression", value);

    lhs.addChildToBack(value);
    return new Node(type, lhs);
  }

  public static Node returnNode() {
    return new Node(Token.RETURN);
  }

  public static Node returnNode(Node expr) {
    checkState(mayBeExpression(expr));
    return new Node(Token.RETURN, expr);
  }

  public static Node yield() {
    return new Node(Token.YIELD);
  }

  public static Node yield(Node expr) {
    checkState(mayBeExpression(expr));
    return new Node(Token.YIELD, expr);
  }

  public static Node await(Node expr) {
    checkState(mayBeExpression(expr));
    return new Node(Token.AWAIT, expr);
  }

  public static Node throwNode(Node expr) {
    checkState(mayBeExpression(expr));
    return new Node(Token.THROW, expr);
  }

  public static Node exprResult(Node expr) {
    checkState(mayBeExpression(expr), expr);
    return new Node(Token.EXPR_RESULT, expr);
  }

  public static Node ifNode(Node cond, Node then) {
    checkState(mayBeExpression(cond));
    checkState(then.isBlock());
    return new Node(Token.IF, cond, then);
  }

  public static Node ifNode(Node cond, Node then, Node elseNode) {
    checkState(mayBeExpression(cond));
    checkState(then.isBlock());
    checkState(elseNode.isBlock());
    return new Node(Token.IF, cond, then, elseNode);
  }

  public static Node doNode(Node body, Node cond) {
    checkState(body.isBlock());
    checkState(mayBeExpression(cond));
    return new Node(Token.DO, body, cond);
  }

  public static Node whileNode(Node cond, Node body) {
    checkState(body.isBlock());
    checkState(mayBeExpression(cond));
    return new Node(Token.WHILE, cond, body);
  }

  public static Node forIn(Node target, Node cond, Node body) {
    checkState(target.isVar() || mayBeExpression(target));
    checkState(mayBeExpression(cond));
    checkState(body.isBlock());
    return new Node(Token.FOR_IN, target, cond, body);
  }

  public static Node forNode(Node init, Node cond, Node incr, Node body) {
    checkState(init.isVar() || init.isLet() || init.isConst() || mayBeExpressionOrEmpty(init));
    checkState(mayBeExpressionOrEmpty(cond));
    checkState(mayBeExpressionOrEmpty(incr));
    checkState(body.isBlock());
    Node r = new Node(Token.FOR, init, cond, incr);
    r.addChildToBack(body);
    return r;
  }

  public static Node switchNode(Node cond, Node... cases) {
    checkState(mayBeExpression(cond));
    Node switchNode = new Node(Token.SWITCH, cond);
    for (Node caseNode : cases) {
      checkState(caseNode.isCase() || caseNode.isDefaultCase());
      switchNode.addChildToBack(caseNode);
    }
    return switchNode;
  }

  public static Node caseNode(Node expr, Node body) {
    checkState(mayBeExpression(expr));
    checkState(body.isBlock());
    body.setIsAddedBlock(true);
    return new Node(Token.CASE, expr, body);
  }

  public static Node defaultCase(Node body) {
    checkState(body.isBlock());
    body.setIsAddedBlock(true);
    return new Node(Token.DEFAULT_CASE, body);
  }

  public static Node label(Node name, Node stmt) {
    // TODO(johnlenz): additional validation here.
    checkState(name.isLabelName());
    checkState(mayBeStatement(stmt));
    Node block = new Node(Token.LABEL, name, stmt);
    return block;
  }

  public static Node labelName(String name) {
    checkState(!name.isEmpty());
    return Node.newString(Token.LABEL_NAME, name);
  }

  public static Node tryFinally(Node tryBody, Node finallyBody) {
    checkState(tryBody.isBlock());
    checkState(finallyBody.isBlock());
    Node catchBody = block().srcrefIfMissing(tryBody);
    return new Node(Token.TRY, tryBody, catchBody, finallyBody);
  }

  public static Node tryCatch(Node tryBody, Node catchNode) {
    checkState(tryBody.isBlock());
    checkState(catchNode.isCatch());
    Node catchBody = blockUnchecked(catchNode).srcrefIfMissing(catchNode);
    return new Node(Token.TRY, tryBody, catchBody);
  }

  public static Node tryCatchFinally(Node tryBody, Node catchNode, Node finallyBody) {
    checkState(finallyBody.isBlock());
    Node tryNode = tryCatch(tryBody, catchNode);
    tryNode.addChildToBack(finallyBody);
    return tryNode;
  }

  public static Node catchNode(Node expr, Node body) {
    checkState(expr.isName());
    checkState(body.isBlock());
    return new Node(Token.CATCH, expr, body);
  }

  public static Node breakNode() {
    return new Node(Token.BREAK);
  }

  public static Node breakNode(Node name) {
    // TODO(johnlenz): additional validation here.
    checkState(name.isLabelName());
    return new Node(Token.BREAK, name);
  }

  public static Node continueNode() {
    return new Node(Token.CONTINUE);
  }

  public static Node continueNode(Node name) {
    // TODO(johnlenz): additional validation here.
    checkState(name.isLabelName());
    return new Node(Token.CONTINUE, name);
  }

  public static Node call(Node target, Node... args) {
    Node call = new Node(Token.CALL, target);
    for (Node arg : args) {
      checkState(mayBeExpression(arg) || arg.isSpread(), arg);
      call.addChildToBack(arg);
    }
    return call;
  }

  public static Node startOptChainCall(Node target, Node... args) {
    Node call = new Node(Token.OPTCHAIN_CALL, target);
    for (Node arg : args) {
      checkState(mayBeExpression(arg) || arg.isSpread(), arg);
      call.addChildToBack(arg);
    }
    call.setIsOptionalChainStart(true);
    return call;
  }

  public static Node continueOptChainCall(Node target, Node... args) {
    Node call = new Node(Token.OPTCHAIN_CALL, target);
    for (Node arg : args) {
      checkState(mayBeExpression(arg) || arg.isSpread(), arg);
      call.addChildToBack(arg);
    }
    call.setIsOptionalChainStart(false);
    return call;
  }

  public static Node newNode(Node target, Node... args) {
    Node newcall = new Node(Token.NEW, target);
    for (Node arg : args) {
      checkState(mayBeExpression(arg) || arg.isSpread(), arg);
      newcall.addChildToBack(arg);
    }
    return newcall;
  }

  public static Node name(String name) {
    Preconditions.checkState(
        name.indexOf('.') == -1, "Invalid name '%s'. Did you mean to use NodeUtil.newQName?", name);
    return Node.newString(Token.NAME, name);
  }

  public static Node startOptChainGetprop(Node target, String prop) {
    checkState(mayBeExpression(target), target);
    Node optChainGetProp = Node.newString(Token.OPTCHAIN_GETPROP, prop);
    optChainGetProp.addChildToBack(target);
    optChainGetProp.setIsOptionalChainStart(true);
    return optChainGetProp;
  }

  public static Node continueOptChainGetprop(Node target, String prop) {
    checkState(mayBeExpression(target), target);
    Node optChainGetProp = Node.newString(Token.OPTCHAIN_GETPROP, prop);
    optChainGetProp.addChildToBack(target);
    optChainGetProp.setIsOptionalChainStart(false);
    return optChainGetProp;
  }

  public static Node getprop(Node target, String prop) {
    checkState(mayBeExpression(target));
    Node getprop = Node.newString(Token.GETPROP, prop);
    getprop.addChildToBack(target);
    return getprop;
  }

  public static Node getprop(Node target, String prop, String... moreProps) {
    checkState(mayBeExpression(target));
    Node result = IR.getprop(target, prop);
    for (String moreProp : moreProps) {
      result = IR.getprop(result, moreProp);
    }
    return result;
  }

  public static Node startOptChainGetelem(Node target, Node elem) {
    checkState(mayBeExpression(target), target);
    checkState(mayBeExpression(elem), elem);
    Node optChainGetElem = new Node(Token.OPTCHAIN_GETELEM, target, elem);
    optChainGetElem.setIsOptionalChainStart(true);
    return optChainGetElem;
  }

  public static Node continueOptChainGetelem(Node target, Node elem) {
    checkState(mayBeExpression(target), target);
    checkState(mayBeExpression(elem), elem);
    Node optChainGetElem = new Node(Token.OPTCHAIN_GETELEM, target, elem);
    optChainGetElem.setIsOptionalChainStart(false);
    return optChainGetElem;
  }

  public static Node getelem(Node target, Node elem) {
    checkState(mayBeExpression(target));
    checkState(mayBeExpression(elem));
    return new Node(Token.GETELEM, target, elem);
  }

  public static Node delprop(Node target) {
    checkState(mayBeExpression(target));
    return new Node(Token.DELPROP, target);
  }

  public static Node assign(Node target, Node expr) {
    checkState(target.isValidAssignmentTarget(), target);
    checkState(mayBeExpression(expr), expr);
    return new Node(Token.ASSIGN, target, expr);
  }

  public static Node hook(Node cond, Node trueval, Node falseval) {
    checkState(mayBeExpression(cond));
    checkState(mayBeExpression(trueval));
    checkState(mayBeExpression(falseval));
    return new Node(Token.HOOK, cond, trueval, falseval);
  }

  public static Node in(Node expr1, Node expr2) {
    return binaryOp(Token.IN, expr1, expr2);
  }

  public static Node comma(Node expr1, Node expr2) {
    return binaryOp(Token.COMMA, expr1, expr2);
  }

  public static Node and(Node expr1, Node expr2) {
    return binaryOp(Token.AND, expr1, expr2);
  }

  public static Node or(Node expr1, Node expr2) {
    return binaryOp(Token.OR, expr1, expr2);
  }

  public static Node coalesce(Node expr1, Node expr2) {
    return binaryOp(Token.COALESCE, expr1, expr2);
  }

  public static Node not(Node expr1) {
    return unaryOp(Token.NOT, expr1);
  }

  /** "<" */
  public static Node lt(Node expr1, Node expr2) {
    return binaryOp(Token.LT, expr1, expr2);
  }

  /** ">=" */
  public static Node ge(Node expr1, Node expr2) {
    return binaryOp(Token.GE, expr1, expr2);
  }

  /** "==" */
  public static Node eq(Node expr1, Node expr2) {
    return binaryOp(Token.EQ, expr1, expr2);
  }

  /** "!=" */
  public static Node ne(Node expr1, Node expr2) {
    return binaryOp(Token.NE, expr1, expr2);
  }

  /** "===" */
  public static Node sheq(Node expr1, Node expr2) {
    return binaryOp(Token.SHEQ, expr1, expr2);
  }

  /** "!==" */
  public static Node shne(Node expr1, Node expr2) {
    return binaryOp(Token.SHNE, expr1, expr2);
  }

  public static Node voidNode(Node expr1) {
    return unaryOp(Token.VOID, expr1);
  }

  public static Node neg(Node expr1) {
    return unaryOp(Token.NEG, expr1);
  }

  public static Node pos(Node expr1) {
    return unaryOp(Token.POS, expr1);
  }

  public static Node cast(Node expr1, JSDocInfo jsdoc) {
    Node op = unaryOp(Token.CAST, expr1);
    op.setJSDocInfo(jsdoc);
    return op;
  }

  public static Node inc(Node exp, boolean isPost) {
    Node op = unaryOp(Token.INC, exp);
    op.putBooleanProp(Node.INCRDECR_PROP, isPost);
    return op;
  }

  public static Node dec(Node exp, boolean isPost) {
    Node op = unaryOp(Token.DEC, exp);
    op.putBooleanProp(Node.INCRDECR_PROP, isPost);
    return op;
  }

  public static Node add(Node expr1, Node expr2) {
    return binaryOp(Token.ADD, expr1, expr2);
  }

  public static Node sub(Node expr1, Node expr2) {
    return binaryOp(Token.SUB, expr1, expr2);
  }

  /** "||=" */
  public static Node assignOr(Node expr1, Node expr2) {
    return binaryOp(Token.ASSIGN_OR, expr1, expr2);
  }

  /** "&&=" */
  public static Node assignAnd(Node expr1, Node expr2) {
    return binaryOp(Token.ASSIGN_AND, expr1, expr2);
  }

  /** "??=" */
  public static Node assignCoalesce(Node expr1, Node expr2) {
    return binaryOp(Token.ASSIGN_COALESCE, expr1, expr2);
  }

  // TODO(johnlenz): the rest of the ops

  // literals
  public static Node objectlit(Node... propdefs) {
    Node objectlit = new Node(Token.OBJECTLIT);
    for (Node propdef : propdefs) {
      switch (propdef.getToken()) {
        case STRING_KEY:
        case MEMBER_FUNCTION_DEF:
        case GETTER_DEF:
        case SETTER_DEF:

        case OBJECT_SPREAD:
        case COMPUTED_PROP:
          break;
        default:
          throw new IllegalStateException("Unexpected OBJECTLIT child: " + propdef);
      }

      objectlit.addChildToBack(propdef);
    }
    return objectlit;
  }

  public static Node objectPattern(Node... keys) {
    Node objectPattern = new Node(Token.OBJECT_PATTERN);
    for (Node key : keys) {
      checkState(key.isStringKey() || key.isComputedProp() || key.isRest());
      objectPattern.addChildToBack(key);
    }
    return objectPattern;
  }

  public static Node arrayPattern(Node... keys) {
    Node arrayPattern = new Node(Token.ARRAY_PATTERN);
    for (Node key : keys) {
      checkState(key.isRest() || key.isValidAssignmentTarget());
      arrayPattern.addChildToBack(key);
    }
    return arrayPattern;
  }

  public static Node computedProp(Node key, Node value) {
    checkState(mayBeExpression(key), key);
    checkState(mayBeExpression(value), value);
    return new Node(Token.COMPUTED_PROP, key, value);
  }

  public static Node propdef(Node string, Node value) {
    checkState(string.isStringKey());
    checkState(!string.hasChildren());
    checkState(mayBeExpression(value));
    string.addChildToFront(value);
    return string;
  }

  public static Node arraylit(Node... exprs) {
    return arraylit(Arrays.asList(exprs));
  }

  public static Node arraylit(Iterable exprs) {
    Node arraylit = new Node(Token.ARRAYLIT);
    for (Node expr : exprs) {
      checkState(mayBeExpressionOrEmpty(expr) || expr.isSpread(), expr);
      arraylit.addChildToBack(expr);
    }
    return arraylit;
  }

  public static Node regexp(Node expr) {
    checkState(expr.isStringLit());
    return new Node(Token.REGEXP, expr);
  }

  public static Node regexp(Node expr, Node flags) {
    checkState(expr.isStringLit());
    checkState(flags.isStringLit());
    return new Node(Token.REGEXP, expr, flags);
  }

  public static Node string(String s) {
    return Node.newString(s);
  }

  public static Node stringKey(String s) {
    return Node.newString(Token.STRING_KEY, s);
  }

  public static Node stringKey(String s, Node value) {
    checkState(mayBeExpression(value) || value.isDefaultValue());
    Node stringKey = stringKey(s);
    stringKey.addChildToFront(value);
    return stringKey;
  }

  public static Node quotedStringKey(String s, Node value) {
    Node k = stringKey(s, value);
    k.putBooleanProp(Node.QUOTED_PROP, true);
    return k;
  }

  public static Node iterRest(Node target) {
    checkState(target.isValidAssignmentTarget(), target);
    return new Node(Token.ITER_REST, target);
  }

  public static Node objectRest(Node target) {
    checkState(target.isValidAssignmentTarget(), target);
    return new Node(Token.OBJECT_REST, target);
  }

  public static Node iterSpread(Node expr) {
    checkState(mayBeExpression(expr));
    return new Node(Token.ITER_SPREAD, expr);
  }

  public static Node objectSpread(Node expr) {
    checkState(mayBeExpression(expr));
    return new Node(Token.OBJECT_SPREAD, expr);
  }

  public static Node superNode() {
    return new Node(Token.SUPER);
  }

  public static Node getterDef(String name, Node value) {
    checkState(value.isFunction());
    Node member = Node.newString(Token.GETTER_DEF, name);
    member.addChildToFront(value);
    return member;
  }

  public static Node setterDef(String name, Node value) {
    checkState(value.isFunction());
    Node member = Node.newString(Token.SETTER_DEF, name);
    member.addChildToFront(value);
    return member;
  }

  public static Node memberFieldDef(String name, Node value) {
    checkState(mayBeExpression(value));
    Node member = Node.newString(Token.MEMBER_FIELD_DEF, name);
    member.addChildToFront(value);
    return member;
  }

  public static Node memberFunctionDef(String name, Node function) {
    checkState(function.isFunction());
    Node member = Node.newString(Token.MEMBER_FUNCTION_DEF, name);
    member.addChildToBack(function);
    return member;
  }

  public static Node number(double d) {
    checkState(!Double.isNaN(d), d);
    checkState(isPositive(d), d);
    return Node.newNumber(d);
  }

  public static Node bigint(BigInteger b) {
    checkNotNull(b);
    checkState(b.signum() >= 0, b);
    return Node.newBigInt(b);
  }

  public static Node thisNode() {
    return new Node(Token.THIS);
  }

  public static Node trueNode() {
    return new Node(Token.TRUE);
  }

  public static Node falseNode() {
    return new Node(Token.FALSE);
  }

  public static Node nullNode() {
    return new Node(Token.NULL);
  }

  public static Node typeof(Node expr) {
    return unaryOp(Token.TYPEOF, expr);
  }

  public static Node importMeta() {
    return new Node(Token.IMPORT_META);
  }

  // helper methods

  private static Node binaryOp(Token token, Node expr1, Node expr2) {
    checkState(mayBeExpression(expr1), expr1);
    checkState(mayBeExpression(expr2), expr2);
    return new Node(token, expr1, expr2);
  }

  private static Node unaryOp(Token token, Node expr) {
    checkState(mayBeExpression(expr));
    return new Node(token, expr);
  }

  private static boolean mayBeExpressionOrEmpty(Node n) {
    return n.isEmpty() || mayBeExpression(n);
  }

  // NOTE: some nodes are neither statements nor expression nodes:
  //   SCRIPT, LABEL_NAME, PARAM_LIST, CASE, DEFAULT_CASE, CATCH
  //   GETTER_DEF, SETTER_DEF

  /**
   * It isn't possible to always determine if a detached node is a expression, so make a best guess.
   */
  private static boolean mayBeStatementNoReturn(Node n) {
    switch (n.getToken()) {
      case EMPTY:
      case FUNCTION:
        // EMPTY and FUNCTION are used both in expression and statement
        // contexts
        return true;

      case BLOCK:
      case BREAK:
      case CLASS:
      case CONST:
      case CONTINUE:
      case DEBUGGER:
      case DO:
      case EXPR_RESULT:
      case FOR:
      case FOR_IN:
      case FOR_OF:
      case FOR_AWAIT_OF:
      case IF:
      case LABEL:
      case LET:
      case SWITCH:
      case THROW:
      case TRY:
      case VAR:
      case WHILE:
      case WITH:
        return true;

      default:
        return false;
    }
  }

  /**
   * It isn't possible to always determine if a detached node is a expression, so make a best guess.
   */
  public static boolean mayBeStatement(Node n) {
    if (!mayBeStatementNoReturn(n)) {
      return n.isReturn();
    }
    return true;
  }

  /**
   * It isn't possible to always determine if a detached node is a expression, so make a best guess.
   */
  public static boolean mayBeExpression(Node n) {
    switch (n.getToken()) {
      case FUNCTION:
      case CLASS:
        // FUNCTION and CLASS are used both in expression and statement
        // contexts.
        return true;

      case ADD:
      case AND:
      case ARRAYLIT:
      case ASSIGN:
      case ASSIGN_BITOR:
      case ASSIGN_BITXOR:
      case ASSIGN_BITAND:
      case ASSIGN_LSH:
      case ASSIGN_RSH:
      case ASSIGN_URSH:
      case ASSIGN_ADD:
      case ASSIGN_SUB:
      case ASSIGN_MUL:
      case ASSIGN_EXPONENT:
      case ASSIGN_DIV:
      case ASSIGN_MOD:
      case ASSIGN_OR:
      case ASSIGN_AND:
      case ASSIGN_COALESCE:
      case AWAIT:
      case BIGINT:
      case BITAND:
      case BITOR:
      case BITNOT:
      case BITXOR:
      case CALL:
      case CAST:
      case COALESCE:
      case COMMA:
      case DEC:
      case DELPROP:
      case DIV:
      case DYNAMIC_IMPORT:
      case EQ:
      case EXPONENT:
      case FALSE:
      case GE:
      case GETPROP:
      case GETELEM:
      case GT:
      case HOOK:
      case IMPORT_META:
      case IN:
      case INC:
      case INSTANCEOF:
      case LE:
      case LSH:
      case LT:
      case MOD:
      case MUL:
      case NAME:
      case NE:
      case NEG:
      case NEW:
      case NEW_TARGET:
      case NOT:
      case NUMBER:
      case NULL:
      case OBJECTLIT:
      case OPTCHAIN_CALL:
      case OPTCHAIN_GETELEM:
      case OPTCHAIN_GETPROP:
      case OR:
      case POS:
      case REGEXP:
      case RSH:
      case SHEQ:
      case SHNE:
      case STRINGLIT:
      case SUB:
      case SUPER:
      case TEMPLATELIT:
      case TAGGED_TEMPLATELIT:
      case THIS:
      case TYPEOF:
      case TRUE:
      case URSH:
      case VOID:
      case YIELD:
        return true;

      default:
        return false;
    }
  }
}