@Override
 public void hotSwapScript(Node scriptRoot, Node originalRoot) {
   Traverser traverser = new Traverser();
   NodeTraversal.traverseEs6(compiler, scriptRoot, traverser);
   if (traverser.changed) {
     compiler.needsEs6Runtime = true;
     compiler.reportCodeChange();
   }
 }
  private void visitForOf(Node node, Node parent) {
    Node variable = node.removeFirstChild();
    Node iterable = node.removeFirstChild();
    Node body = node.removeFirstChild();

    Node iterName = IR.name(ITER_BASE + compiler.getUniqueNameIdSupplier().get());
    Node getNext = IR.call(IR.getprop(iterName.cloneTree(), IR.string("next")));
    String variableName;
    int declType;
    if (variable.isName()) {
      declType = Token.NAME;
      variableName = variable.getQualifiedName();
    } else {
      Preconditions.checkState(
          NodeUtil.isNameDeclaration(variable), "Expected var, let, or const. Got %s", variable);
      declType = variable.getType();
      variableName = variable.getFirstChild().getQualifiedName();
    }
    Node iterResult = IR.name(ITER_RESULT + variableName);

    Node makeIter = IR.call(NodeUtil.newQName(compiler, MAKE_ITER), iterable);
    compiler.needsEs6Runtime = true;

    Node init = IR.var(iterName.cloneTree(), makeIter);
    Node initIterResult = iterResult.cloneTree();
    initIterResult.addChildToFront(getNext.cloneTree());
    init.addChildToBack(initIterResult);

    Node cond = IR.not(IR.getprop(iterResult.cloneTree(), IR.string("done")));
    Node incr = IR.assign(iterResult.cloneTree(), getNext.cloneTree());

    Node declarationOrAssign;
    if (declType == Token.NAME) {
      declarationOrAssign =
          IR.exprResult(
              IR.assign(
                  IR.name(variableName), IR.getprop(iterResult.cloneTree(), IR.string("value"))));
    } else {
      declarationOrAssign = new Node(declType, IR.name(variableName));
      declarationOrAssign
          .getFirstChild()
          .addChildToBack(IR.getprop(iterResult.cloneTree(), IR.string("value")));
    }
    body.addChildToFront(declarationOrAssign);

    Node newFor = IR.forNode(init, cond, incr, body);
    newFor.useSourceInfoIfMissingFromForTree(node);
    parent.replaceChild(node, newFor);
    compiler.reportCodeChange();
  }
  /**
   * Classes are processed in 3 phases:
   *
   * <ol>
   *   <li>The class name is extracted.
   *   <li>Class members are processed and rewritten.
   *   <li>The constructor is built.
   * </ol>
   */
  private void visitClass(Node classNode, Node parent) {
    checkClassReassignment(classNode);
    // Collect Metadata
    ClassDeclarationMetadata metadata = ClassDeclarationMetadata.create(classNode, parent);

    if (metadata == null || metadata.fullClassName == null) {
      cannotConvert(
          parent,
          "Can only convert classes that are declarations or the right hand"
              + " side of a simple assignment.");
      return;
    }
    if (metadata.hasSuperClass() && !metadata.superClassNameNode.isQualifiedName()) {
      compiler.report(JSError.make(metadata.superClassNameNode, DYNAMIC_EXTENDS_TYPE));
      return;
    }

    boolean useUnique = NodeUtil.isStatement(classNode) && !NodeUtil.isInFunction(classNode);
    String uniqueFullClassName =
        useUnique ? getUniqueClassName(metadata.fullClassName) : metadata.fullClassName;
    Node classNameAccess = NodeUtil.newQName(compiler, uniqueFullClassName);
    Node prototypeAccess = NodeUtil.newPropertyAccess(compiler, classNameAccess, "prototype");

    Preconditions.checkState(
        NodeUtil.isStatement(metadata.insertionPoint),
        "insertion point must be a statement: %s",
        metadata.insertionPoint);

    Node constructor = null;
    JSDocInfo ctorJSDocInfo = null;
    // Process all members of the class
    Node classMembers = classNode.getLastChild();
    Map<String, JSDocInfo> prototypeMembersToDeclare = new LinkedHashMap<>();
    Map<String, JSDocInfo> classMembersToDeclare = new LinkedHashMap<>();
    for (Node member : classMembers.children()) {
      if (member.isEmpty()) {
        continue;
      }
      Preconditions.checkState(
          member.isMemberFunctionDef()
              || member.isGetterDef()
              || member.isSetterDef()
              || (member.isComputedProp() && !member.getBooleanProp(Node.COMPUTED_PROP_VARIABLE)),
          "Member variables should have been transpiled earlier: ",
          member);

      if (member.isGetterDef() || member.isSetterDef()) {
        JSTypeExpression typeExpr = getTypeFromGetterOrSetter(member).clone();
        addToDefinePropertiesObject(metadata, member);

        Map<String, JSDocInfo> membersToDeclare =
            member.isStaticMember() ? classMembersToDeclare : prototypeMembersToDeclare;
        JSDocInfo existingJSDoc = membersToDeclare.get(member.getString());
        JSTypeExpression existingType = existingJSDoc == null ? null : existingJSDoc.getType();
        if (existingType != null && !existingType.equals(typeExpr)) {
          compiler.report(JSError.make(member, CONFLICTING_GETTER_SETTER_TYPE, member.getString()));
        } else {
          JSDocInfoBuilder jsDoc = new JSDocInfoBuilder(false);
          jsDoc.recordType(typeExpr);
          if (member.getJSDocInfo() != null && member.getJSDocInfo().isExport()) {
            jsDoc.recordExport();
          }
          if (member.isStaticMember()) {
            jsDoc.recordNoCollapse();
          }
          membersToDeclare.put(member.getString(), jsDoc.build());
        }
      } else if (member.isMemberFunctionDef() && member.getString().equals("constructor")) {
        ctorJSDocInfo = member.getJSDocInfo();
        constructor = member.getFirstChild().detachFromParent();
        if (!metadata.anonymous) {
          // Turns class Foo { constructor: function() {} } into function Foo() {},
          // i.e. attaches the name the ctor function.
          constructor.replaceChild(constructor.getFirstChild(), metadata.classNameNode.cloneNode());
        }
      } else {
        Node qualifiedMemberAccess =
            getQualifiedMemberAccess(compiler, member, classNameAccess, prototypeAccess);
        Node method = member.getLastChild().detachFromParent();

        Node assign = IR.assign(qualifiedMemberAccess, method);
        assign.useSourceInfoIfMissingFromForTree(member);

        JSDocInfo info = member.getJSDocInfo();
        if (member.isStaticMember() && NodeUtil.referencesThis(assign.getLastChild())) {
          JSDocInfoBuilder memberDoc = JSDocInfoBuilder.maybeCopyFrom(info);
          memberDoc.recordThisType(
              new JSTypeExpression(
                  new Node(Token.BANG, new Node(Token.QMARK)), member.getSourceFileName()));
          info = memberDoc.build();
        }
        if (info != null) {
          assign.setJSDocInfo(info);
        }

        Node newNode = NodeUtil.newExpr(assign);
        metadata.insertNodeAndAdvance(newNode);
      }
    }

    // Add declarations for properties that were defined with a getter and/or setter,
    // so that the typechecker knows those properties exist on the class.
    // This is a temporary solution. Eventually, the type checker should understand
    // Object.defineProperties calls directly.
    for (Map.Entry<String, JSDocInfo> entry : prototypeMembersToDeclare.entrySet()) {
      String declaredMember = entry.getKey();
      Node declaration = IR.getprop(prototypeAccess.cloneTree(), IR.string(declaredMember));
      declaration.setJSDocInfo(entry.getValue());
      metadata.insertNodeAndAdvance(
          IR.exprResult(declaration).useSourceInfoIfMissingFromForTree(classNode));
    }
    for (Map.Entry<String, JSDocInfo> entry : classMembersToDeclare.entrySet()) {
      String declaredMember = entry.getKey();
      Node declaration = IR.getprop(classNameAccess.cloneTree(), IR.string(declaredMember));
      declaration.setJSDocInfo(entry.getValue());
      metadata.insertNodeAndAdvance(
          IR.exprResult(declaration).useSourceInfoIfMissingFromForTree(classNode));
    }

    if (metadata.definePropertiesObjForPrototype.hasChildren()) {
      Node definePropsCall =
          IR.exprResult(
              IR.call(
                  NodeUtil.newQName(compiler, "Object.defineProperties"),
                  prototypeAccess.cloneTree(),
                  metadata.definePropertiesObjForPrototype));
      definePropsCall.useSourceInfoIfMissingFromForTree(classNode);
      metadata.insertNodeAndAdvance(definePropsCall);
    }

    if (metadata.definePropertiesObjForClass.hasChildren()) {
      Node definePropsCall =
          IR.exprResult(
              IR.call(
                  NodeUtil.newQName(compiler, "Object.defineProperties"),
                  classNameAccess.cloneTree(),
                  metadata.definePropertiesObjForClass));
      definePropsCall.useSourceInfoIfMissingFromForTree(classNode);
      metadata.insertNodeAndAdvance(definePropsCall);
    }

    Preconditions.checkNotNull(constructor);

    JSDocInfo classJSDoc = NodeUtil.getBestJSDocInfo(classNode);
    JSDocInfoBuilder newInfo = JSDocInfoBuilder.maybeCopyFrom(classJSDoc);

    newInfo.recordConstructor();

    if (metadata.hasSuperClass()) {
      String superClassString = metadata.superClassNameNode.getQualifiedName();
      if (newInfo.isInterfaceRecorded()) {
        newInfo.recordExtendedInterface(
            new JSTypeExpression(
                new Node(Token.BANG, IR.string(superClassString)),
                metadata.superClassNameNode.getSourceFileName()));
      } else {
        Node inherits =
            IR.call(
                NodeUtil.newQName(compiler, INHERITS),
                NodeUtil.newQName(compiler, metadata.fullClassName),
                NodeUtil.newQName(compiler, superClassString));
        Node inheritsCall = IR.exprResult(inherits);
        compiler.needsEs6Runtime = true;

        inheritsCall.useSourceInfoIfMissingFromForTree(classNode);
        Node enclosingStatement = NodeUtil.getEnclosingStatement(classNode);
        enclosingStatement.getParent().addChildAfter(inheritsCall, enclosingStatement);
        newInfo.recordBaseType(
            new JSTypeExpression(
                new Node(Token.BANG, IR.string(superClassString)),
                metadata.superClassNameNode.getSourceFileName()));
      }
    }

    // Classes are @struct by default.
    if (!newInfo.isUnrestrictedRecorded()
        && !newInfo.isDictRecorded()
        && !newInfo.isStructRecorded()) {
      newInfo.recordStruct();
    }

    if (ctorJSDocInfo != null) {
      newInfo.recordSuppressions(ctorJSDocInfo.getSuppressions());
      for (String param : ctorJSDocInfo.getParameterNames()) {
        newInfo.recordParameter(param, ctorJSDocInfo.getParameterType(param));
      }
      newInfo.mergePropertyBitfieldFrom(ctorJSDocInfo);
    }

    if (NodeUtil.isStatement(classNode)) {
      constructor.getFirstChild().setString("");
      Node ctorVar = IR.let(metadata.classNameNode.cloneNode(), constructor);
      ctorVar.useSourceInfoIfMissingFromForTree(classNode);
      parent.replaceChild(classNode, ctorVar);
    } else {
      parent.replaceChild(classNode, constructor);
    }

    if (NodeUtil.isStatement(constructor)) {
      constructor.setJSDocInfo(newInfo.build());
    } else if (parent.isName()) {
      // The constructor function is the RHS of a var statement.
      // Add the JSDoc to the VAR node.
      Node var = parent.getParent();
      var.setJSDocInfo(newInfo.build());
    } else if (constructor.getParent().isName()) {
      // Is a newly created VAR node.
      Node var = constructor.getParent().getParent();
      var.setJSDocInfo(newInfo.build());
    } else if (parent.isAssign()) {
      // The constructor function is the RHS of an assignment.
      // Add the JSDoc to the ASSIGN node.
      parent.setJSDocInfo(newInfo.build());
    } else {
      throw new IllegalStateException("Unexpected parent node " + parent);
    }

    compiler.reportCodeChange();
  }