Implement modular compilation

lib/src/js/printer.dart

-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-part of js_ast;
-
-
-class JavaScriptPrintingOptions {
-  final bool shouldCompressOutput;
-  final bool minifyLocalVariables;
-  final bool preferSemicolonToNewlineInMinifiedOutput;
-  final bool emitTypes;
-  final bool allowSingleLineIfStatements;
-
-  /// True to allow keywords in properties, such as `obj.var` or `obj.function`
-  /// Modern JS engines support this.
-  final bool allowKeywordsInProperties;
-
-  JavaScriptPrintingOptions(
-      {this.shouldCompressOutput: false,
-       this.minifyLocalVariables: false,
-       this.preferSemicolonToNewlineInMinifiedOutput: false,
-       this.emitTypes: false,
-       this.allowKeywordsInProperties: false,
-       this.allowSingleLineIfStatements: false});
-}
-
-
-/// An environment in which JavaScript printing is done.  Provides emitting of
-/// text and pre- and post-visit callbacks.
-abstract class JavaScriptPrintingContext {
-  /// Signals an error.  This should happen only for serious internal errors.
-  void error(String message) { throw message; }
-
-  /// Adds [string] to the output.
-  void emit(String string);
-
-  /// Callback immediately before printing [node].  Whitespace may be printed
-  /// after this callback before the first non-whitespace character for [node].
-  void enterNode(Node node) {}
-  /// Callback after printing the last character representing [node].
-  void exitNode(Node node) {}
-}
-
-/// A simple implementation of [JavaScriptPrintingContext] suitable for tests.
-class SimpleJavaScriptPrintingContext extends JavaScriptPrintingContext {
-  final StringBuffer buffer = new StringBuffer();
-
-  void emit(String string) {
-    buffer.write(string);
-  }
-
-  String getText() => buffer.toString();
-}
-
-// TODO(ochafik): Inline the body of [TypeScriptTypePrinter] here if/when it no
-// longer needs to share utils with [ClosureTypePrinter].
-class Printer extends TypeScriptTypePrinter implements NodeVisitor {
-  final JavaScriptPrintingOptions options;
-  final JavaScriptPrintingContext context;
-  final bool shouldCompressOutput;
-  final DanglingElseVisitor danglingElseVisitor;
-  final LocalNamer localNamer;
-
-  bool inForInit = false;
-  bool atStatementBegin = false;
-  bool inNewTarget = false;
-  bool pendingSemicolon = false;
-  bool pendingSpace = false;
-
-  // The current indentation level.
-  int _indentLevel = 0;
-  // A cache of all indentation strings used so far.
-  List<String> _indentList = <String>[""];
-  /// Whether the next call to [indent] should just be a no-op.
-  bool _skipNextIndent = false;
-
-  static final identifierCharacterRegExp = new RegExp(r'^[a-zA-Z_0-9$]');
-  static final expressionContinuationRegExp = new RegExp(r'^[-+([]');
-
-  Printer(JavaScriptPrintingOptions options,
-          JavaScriptPrintingContext context,
-          {LocalNamer localNamer})
-      : options = options,
-        context = context,
-        shouldCompressOutput = options.shouldCompressOutput,
-        danglingElseVisitor = new DanglingElseVisitor(context),
-        localNamer = determineRenamer(localNamer, options);
-
-  static LocalNamer determineRenamer(LocalNamer localNamer,
-                                     JavaScriptPrintingOptions options) {
-    if (localNamer != null) return localNamer;
-    return (options.shouldCompressOutput && options.minifyLocalVariables)
-        ? new MinifyRenamer() : new IdentityNamer();
-  }
-
-
-  // The current indentation string.
-  String get indentation {
-    // Lazily add new indentation strings as required.
-    while (_indentList.length <= _indentLevel) {
-      _indentList.add(_indentList.last + "  ");
-    }
-    return _indentList[_indentLevel];
-  }
-
-  void indentMore() {
-    _indentLevel++;
-  }
-
-  void indentLess() {
-    _indentLevel--;
-  }
-
-
-  /// Always emit a newline, even under `enableMinification`.
-  void forceLine() {
-    out("\n");
-  }
-  /// Emits a newline for readability.
-  void lineOut() {
-    if (!shouldCompressOutput) forceLine();
-  }
-  void spaceOut() {
-    if (!shouldCompressOutput) out(" ");
-  }
-
-  String lastAddedString = null;
-  int get lastCharCode {
-    if (lastAddedString == null) return 0;
-    assert(lastAddedString.length != "");
-    return lastAddedString.codeUnitAt(lastAddedString.length - 1);
-  }
-
-  void out(String str) {
-    if (str != "") {
-      if (pendingSemicolon) {
-        if (!shouldCompressOutput) {
-          context.emit(";");
-        } else if (str != "}") {
-          // We want to output newline instead of semicolon because it makes
-          // the raw stack traces much easier to read and it also makes line-
-          // based tools like diff work much better.  JavaScript will
-          // automatically insert the semicolon at the newline if it means a
-          // parsing error is avoided, so we can only do this trick if the
-          // next line is not something that can be glued onto a valid
-          // expression to make a new valid expression.
-
-          // If we're using the new emitter where most pretty printed code
-          // is escaped in strings, it is a lot easier to deal with semicolons
-          // than newlines because the former doesn't need escaping.
-          if (options.preferSemicolonToNewlineInMinifiedOutput ||
-              expressionContinuationRegExp.hasMatch(str)) {
-            context.emit(";");
-          } else {
-            context.emit("\n");
-          }
-        }
-      }
-      if (pendingSpace &&
-          (!shouldCompressOutput || identifierCharacterRegExp.hasMatch(str))) {
-        context.emit(" ");
-      }
-      pendingSpace = false;
-      pendingSemicolon = false;
-      context.emit(str);
-      lastAddedString = str;
-    }
-  }
-
-  void outLn(String str) {
-    out(str);
-    lineOut();
-  }
-
-  void outSemicolonLn() {
-    if (shouldCompressOutput) {
-      pendingSemicolon = true;
-    } else {
-      out(";");
-      forceLine();
-    }
-  }
-
-  void outIndent(String str) { indent(); out(str); }
-  void outIndentLn(String str) { indent(); outLn(str); }
-
-  void skipNextIndent() {
-    _skipNextIndent = true;
-  }
-
-  void indent() {
-    if (_skipNextIndent) {
-      _skipNextIndent = false;
-      return;
-    }
-    if (!shouldCompressOutput) {
-      out(indentation);
-    }
-  }
-
-  visit(Node node) {
-    context.enterNode(node);
-    node.accept(this);
-    context.exitNode(node);
-  }
-
-  visitCommaSeparated(List<Node> nodes, int hasRequiredType,
-                      {bool newInForInit, bool newAtStatementBegin}) {
-    for (int i = 0; i < nodes.length; i++) {
-      if (i != 0) {
-        atStatementBegin = false;
-        out(",");
-        spaceOut();
-      }
-      visitNestedExpression(nodes[i], hasRequiredType,
-                            newInForInit: newInForInit,
-                            newAtStatementBegin: newAtStatementBegin);
-    }
-  }
-
-  visitAll(List<Node> nodes) {
-    nodes.forEach(visit);
-  }
-
-  visitProgram(Program program) {
-    if (program.scriptTag != null) {
-      out('#!${program.scriptTag}\n');
-    }
-    visitAll(program.body);
-  }
-
-  bool blockBody(Node body, {bool needsSeparation, bool needsNewline}) {
-    if (body is Block) {
-      spaceOut();
-      blockOut(body, false, needsNewline);
-      return true;
-    }
-    if (shouldCompressOutput && needsSeparation) {
-      // If [shouldCompressOutput] is false, then the 'lineOut' will insert
-      // the separation.
-      out(" ");
-    } else {
-      lineOut();
-    }
-    indentMore();
-    visit(body);
-    indentLess();
-    return false;
-  }
-
-  void blockOutWithoutBraces(Node node) {
-    if (node is Block && !node.isScope) {
-      context.enterNode(node);
-      Block block = node;
-      block.statements.forEach(blockOutWithoutBraces);
-      context.exitNode(node);
-    } else {
-      visit(node);
-    }
-  }
-
-  void blockOut(Block node, bool shouldIndent, bool needsNewline) {
-    if (shouldIndent) indent();
-    context.enterNode(node);
-    out("{");
-    lineOut();
-    indentMore();
-    node.statements.forEach(blockOutWithoutBraces);
-    indentLess();
-    indent();
-    out("}");
-    context.exitNode(node);
-    if (needsNewline) lineOut();
-  }
-
-  visitBlock(Block block) {
-    blockOut(block, true, true);
-  }
-
-  visitExpressionStatement(ExpressionStatement expressionStatement) {
-    indent();
-    outClosureAnnotation(expressionStatement);
-    visitNestedExpression(expressionStatement.expression, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: true);
-    outSemicolonLn();
-  }
-
-  visitEmptyStatement(EmptyStatement nop) {
-    outIndentLn(";");
-  }
-
-  void ifOut(If node, bool shouldIndent) {
-    Node then = node.then;
-    Node elsePart = node.otherwise;
-    bool hasElse = node.hasElse;
-
-    // Handle dangling elses and a work-around for Android 4.0 stock browser.
-    // Android 4.0 requires braces for a single do-while in the `then` branch.
-    // See issue 10923.
-    if (hasElse) {
-      bool needsBraces = node.then.accept(danglingElseVisitor) || then is Do;
-      if (needsBraces) {
-        then = new Block(<Statement>[then]);
-      }
-    }
-    if (shouldIndent) indent();
-    out("if");
-    spaceOut();
-    out("(");
-    visitNestedExpression(node.condition, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    out(")");
-    bool thenWasBlock;
-    if (options.allowSingleLineIfStatements && !hasElse && then is! Block) {
-      thenWasBlock = false;
-      spaceOut();
-      skipNextIndent();
-      visit(then);
-    } else {
-      thenWasBlock =
-          blockBody(then, needsSeparation: false, needsNewline: !hasElse);
-    }
-    if (hasElse) {
-      if (thenWasBlock) {
-        spaceOut();
-      } else {
-        indent();
-      }
-      out("else");
-      if (elsePart is If) {
-        pendingSpace = true;
-        ifOut(elsePart, false);
-      } else {
-        blockBody(elsePart, needsSeparation: true, needsNewline: true);
-      }
-    }
-  }
-
-  visitIf(If node) {
-    ifOut(node, true);
-  }
-
-  visitFor(For loop) {
-    outIndent("for");
-    spaceOut();
-    out("(");
-    if (loop.init != null) {
-      visitNestedExpression(loop.init, EXPRESSION,
-                            newInForInit: true, newAtStatementBegin: false);
-    }
-    out(";");
-    if (loop.condition != null) {
-      spaceOut();
-      visitNestedExpression(loop.condition, EXPRESSION,
-                            newInForInit: false, newAtStatementBegin: false);
-    }
-    out(";");
-    if (loop.update != null) {
-      spaceOut();
-      visitNestedExpression(loop.update, EXPRESSION,
-                            newInForInit: false, newAtStatementBegin: false);
-    }
-    out(")");
-    blockBody(loop.body, needsSeparation: false, needsNewline: true);
-  }
-
-  visitForIn(ForIn loop) {
-    outIndent("for");
-    spaceOut();
-    out("(");
-    visitNestedExpression(loop.leftHandSide, EXPRESSION,
-                          newInForInit: true, newAtStatementBegin: false);
-    out(" in");
-    pendingSpace = true;
-    visitNestedExpression(loop.object, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    out(")");
-    blockBody(loop.body, needsSeparation: false, needsNewline: true);
-  }
-
-  visitForOf(ForOf loop) {
-    outIndent("for");
-    spaceOut();
-    out("(");
-    visitNestedExpression(loop.leftHandSide, EXPRESSION,
-    newInForInit: true, newAtStatementBegin: false);
-    out(" of");
-    pendingSpace = true;
-    visitNestedExpression(loop.iterable, EXPRESSION,
-    newInForInit: false, newAtStatementBegin: false);
-    out(")");
-    blockBody(loop.body, needsSeparation: false, needsNewline: true);
-  }
-
-  visitWhile(While loop) {
-    outIndent("while");
-    spaceOut();
-    out("(");
-    visitNestedExpression(loop.condition, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    out(")");
-    blockBody(loop.body, needsSeparation: false, needsNewline: true);
-  }
-
-  visitDo(Do loop) {
-    outIndent("do");
-    if (blockBody(loop.body, needsSeparation: true, needsNewline: false)) {
-      spaceOut();
-    } else {
-      indent();
-    }
-    out("while");
-    spaceOut();
-    out("(");
-    visitNestedExpression(loop.condition, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    out(")");
-    outSemicolonLn();
-  }
-
-  visitContinue(Continue node) {
-    if (node.targetLabel == null) {
-      outIndent("continue");
-    } else {
-      outIndent("continue ${node.targetLabel}");
-    }
-    outSemicolonLn();
-  }
-
-  visitBreak(Break node) {
-    if (node.targetLabel == null) {
-      outIndent("break");
-    } else {
-      outIndent("break ${node.targetLabel}");
-    }
-    outSemicolonLn();
-  }
-
-  visitReturn(Return node) {
-    if (node.value == null) {
-      outIndent("return");
-    } else {
-      outIndent("return");
-      pendingSpace = true;
-      visitNestedExpression(node.value, EXPRESSION,
-                            newInForInit: false, newAtStatementBegin: false);
-    }
-    outSemicolonLn();
-  }
-
-  visitDartYield(DartYield node) {
-    if (node.hasStar) {
-      outIndent("yield*");
-    } else {
-      outIndent("yield");
-    }
-    pendingSpace = true;
-    visitNestedExpression(node.expression, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    outSemicolonLn();
-  }
-
-
-  visitThrow(Throw node) {
-    outIndent("throw");
-    pendingSpace = true;
-    visitNestedExpression(node.expression, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    outSemicolonLn();
-  }
-
-  visitTry(Try node) {
-    outIndent("try");
-    blockBody(node.body, needsSeparation: true, needsNewline: false);
-    if (node.catchPart != null) {
-      visit(node.catchPart);
-    }
-    if (node.finallyPart != null) {
-      spaceOut();
-      out("finally");
-      blockBody(node.finallyPart, needsSeparation: true, needsNewline: true);
-    } else {
-      lineOut();
-    }
-  }
-
-  visitCatch(Catch node) {
-    spaceOut();
-    out("catch");
-    spaceOut();
-    out("(");
-    visitNestedExpression(node.declaration, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    out(")");
-    blockBody(node.body, needsSeparation: false, needsNewline: true);
-  }
-
-  visitSwitch(Switch node) {
-    outIndent("switch");
-    spaceOut();
-    out("(");
-    visitNestedExpression(node.key, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    out(")");
-    spaceOut();
-    outLn("{");
-    indentMore();
-    visitAll(node.cases);
-    indentLess();
-    outIndentLn("}");
-  }
-
-  visitCase(Case node) {
-    outIndent("case");
-    pendingSpace = true;
-    visitNestedExpression(node.expression, EXPRESSION,
-                          newInForInit: false, newAtStatementBegin: false);
-    outLn(":");
-    if (!node.body.statements.isEmpty) {
-      blockOut(node.body, true, true);
-    }
-  }
-
-  visitDefault(Default node) {
-    outIndentLn("default:");
-    if (!node.body.statements.isEmpty) {
-      blockOut(node.body, true, true);
-    }
-  }
-
-  visitLabeledStatement(LabeledStatement node) {
-    outIndent("${node.label}:");
-    blockBody(node.body, needsSeparation: false, needsNewline: true);
-  }
-
-  void functionOut(Fun fun, Node name) {
-    out("function");
-    if (fun.isGenerator) out("*");
-    if (name != null) {
-      out(" ");
-      // Name must be a [Decl]. Therefore only test for primary expressions.
-      visitNestedExpression(name, PRIMARY,
-                            newInForInit: false, newAtStatementBegin: false);
-    }
-    localNamer.enterScope(fun);
-    outTypeParams(fun.typeParams);
-    out("(");
-    if (fun.params != null) {
-      visitCommaSeparated(fun.params, PRIMARY,
-                          newInForInit: false, newAtStatementBegin: false);
-    }
-    out(")");
-    outTypeAnnotation(fun.returnType);
-    switch (fun.asyncModifier) {
-      case const AsyncModifier.sync():
-        break;
-      case const AsyncModifier.async():
-        out(' async');
-        break;
-      case const AsyncModifier.syncStar():
-        out(' sync*');
-        break;
-      case const AsyncModifier.asyncStar():
-        out(' async*');
-        break;
-    }
-    blockBody(fun.body, needsSeparation: false, needsNewline: false);
-    localNamer.leaveScope();
-  }
-
-  visitFunctionDeclaration(FunctionDeclaration declaration) {
-    indent();
-    outClosureAnnotation(declaration);
-    functionOut(declaration.function, declaration.name);
-    lineOut();
-  }
-
-  visitNestedExpression(Expression node, int requiredPrecedence,
-                        {bool newInForInit, bool newAtStatementBegin}) {
-    int nodePrecedence = node.precedenceLevel;
-    bool needsParentheses =
-        // a - (b + c).
-        (requiredPrecedence != EXPRESSION &&
-         nodePrecedence < requiredPrecedence) ||
-        // for (a = (x in o); ... ; ... ) { ... }
-        (newInForInit && node is Binary && node.op == "in") ||
-        // (function() { ... })().
-        // ({a: 2, b: 3}.toString()).
-        (newAtStatementBegin && (node is NamedFunction ||
-                                 node is FunctionExpression ||
-                                 node is ObjectInitializer));
-    if (needsParentheses) {
-      inForInit = false;
-      atStatementBegin = false;
-      inNewTarget = false;
-      out("(");
-      visit(node);
-      out(")");
-    } else {
-      inForInit = newInForInit;
-      atStatementBegin = newAtStatementBegin;
-      visit(node);
-    }
-  }
-
-  visitVariableDeclarationList(VariableDeclarationList list) {
-    outClosureAnnotation(list);
-    // Note: keyword can be null for non-static field declarations.
-    if (list.keyword != null) {
-      out(list.keyword);
-      out(" ");
-    }
-    visitCommaSeparated(list.declarations, ASSIGNMENT,
-                        newInForInit: inForInit, newAtStatementBegin: false);
-  }
-
-  visitArrayBindingPattern(ArrayBindingPattern node) {
-    out("[");
-    visitCommaSeparated(node.variables, EXPRESSION,
-                        newInForInit: false, newAtStatementBegin: false);
-    out("]");
-  }
-  visitObjectBindingPattern(ObjectBindingPattern node) {
-    out("{");
-    visitCommaSeparated(node.variables, EXPRESSION,
-                        newInForInit: false, newAtStatementBegin: false);
-    out("}");
-  }
-
-  visitDestructuredVariable(DestructuredVariable node) {
-    var name = node.name;
-    var hasName = name != null;
-    if (hasName) {
-      if (name is LiteralString) {
-        out("[");
-        out(name.value);
-        out("]");
-      } else {
-        visit(name);
-      }
-    }
-    if (node.structure != null) {
-      if (hasName) {
-        out(":");
-        spaceOut();
-      }
-      visit(node.structure);
-    }
-    outTypeAnnotation(node.type);
-    if (node.defaultValue != null) {
-      spaceOut();
-      out("=");
-      spaceOut();
-      visitNestedExpression(node.defaultValue, EXPRESSION,
-                            newInForInit: false, newAtStatementBegin: false);
-    }
-  }
-
-  visitSimpleBindingPattern(SimpleBindingPattern node) {
-    visit(node.name);
-  }
-
-  visitAssignment(Assignment assignment) {
-    visitNestedExpression(assignment.leftHandSide, LEFT_HAND_SIDE,
-                          newInForInit: inForInit,
-                          newAtStatementBegin: atStatementBegin);
-    if (assignment.value != null) {
-      spaceOut();
-      String op = assignment.op;
-      if (op != null) out(op);
-      out("=");
-      spaceOut();
-      visitNestedExpression(assignment.value, ASSIGNMENT,
-                            newInForInit: inForInit,
-                            newAtStatementBegin: false);
-    }
-  }
-
-  visitVariableInitialization(VariableInitialization initialization) {
-    outClosureAnnotation(initialization);
-    visitAssignment(initialization);
-  }
-
-  visitConditional(Conditional cond) {
-    visitNestedExpression(cond.condition, LOGICAL_OR,
-                          newInForInit: inForInit,
-                          newAtStatementBegin: atStatementBegin);
-    spaceOut();
-    out("?");
-    spaceOut();
-    // The then part is allowed to have an 'in'.
-    visitNestedExpression(cond.then, ASSIGNMENT,
-                          newInForInit: false, newAtStatementBegin: false);
-    spaceOut();
-    out(":");
-    spaceOut();
-    visitNestedExpression(cond.otherwise, ASSIGNMENT,
-                          newInForInit: inForInit, newAtStatementBegin: false);
-  }
-
-  visitNew(New node) {
-    out("new ");
-    inNewTarget = true;
-    visitNestedExpression(node.target, ACCESS,
-                          newInForInit: inForInit, newAtStatementBegin: false);
-    inNewTarget = false;
-    out("(");
-    visitCommaSeparated(node.arguments, SPREAD,
-                        newInForInit: false, newAtStatementBegin: false);
-    out(")");
-  }
-
-  visitCall(Call call) {
-    visitNestedExpression(call.target, LEFT_HAND_SIDE,
-                          newInForInit: inForInit,
-                          newAtStatementBegin: atStatementBegin);
-    out("(");
-    visitCommaSeparated(call.arguments, SPREAD,
-                        newInForInit: false, newAtStatementBegin: false);
-    out(")");
-  }
-
-  visitBinary(Binary binary) {
-    Expression left = binary.left;
-    Expression right = binary.right;
-    String op = binary.op;
-    int leftPrecedenceRequirement;
-    int rightPrecedenceRequirement;
-    bool leftSpace = true;   // left<HERE>op right
-    switch (op) {
-      case ',':
-        //  x, (y, z) <=> (x, y), z.
-        leftPrecedenceRequirement = EXPRESSION;
-        rightPrecedenceRequirement = EXPRESSION;
-        leftSpace = false;
-        break;
-      case "||":
-        leftPrecedenceRequirement = LOGICAL_OR;
-        // x || (y || z) <=> (x || y) || z.
-        rightPrecedenceRequirement = LOGICAL_OR;
-        break;
-      case "&&":
-        leftPrecedenceRequirement = LOGICAL_AND;
-        // x && (y && z) <=> (x && y) && z.
-        rightPrecedenceRequirement = LOGICAL_AND;
-        break;
-      case "|":
-        leftPrecedenceRequirement = BIT_OR;
-        // x | (y | z) <=> (x | y) | z.
-        rightPrecedenceRequirement = BIT_OR;
-        break;
-      case "^":
-        leftPrecedenceRequirement = BIT_XOR;
-        // x ^ (y ^ z) <=> (x ^ y) ^ z.
-        rightPrecedenceRequirement = BIT_XOR;
-        break;
-      case "&":
-        leftPrecedenceRequirement = BIT_AND;
-        // x & (y & z) <=> (x & y) & z.
-        rightPrecedenceRequirement = BIT_AND;
-        break;
-      case "==":
-      case "!=":
-      case "===":
-      case "!==":
-        leftPrecedenceRequirement = EQUALITY;
-        rightPrecedenceRequirement = RELATIONAL;
-        break;
-      case "<":
-      case ">":
-      case "<=":
-      case ">=":
-      case "instanceof":
-      case "in":
-        leftPrecedenceRequirement = RELATIONAL;
-        rightPrecedenceRequirement = SHIFT;
-        break;
-      case ">>":
-      case "<<":
-      case ">>>":
-        leftPrecedenceRequirement = SHIFT;
-        rightPrecedenceRequirement = ADDITIVE;
-        break;
-      case "+":
-      case "-":
-        leftPrecedenceRequirement = ADDITIVE;
-        // We cannot remove parenthesis for "+" because
-        //   x + (y + z) <!=> (x + y) + z:
-        // Example:
-        //   "a" + (1 + 2) => "a3";
-        //   ("a" + 1) + 2 => "a12";
-        rightPrecedenceRequirement = MULTIPLICATIVE;
-        break;
-      case "*":
-      case "/":
-      case "%":
-        leftPrecedenceRequirement = MULTIPLICATIVE;
-        // We cannot remove parenthesis for "*" because of precision issues.
-        rightPrecedenceRequirement = UNARY;
-        break;
-      default:
-        context.error("Forgot operator: $op");
-    }
-
-    visitNestedExpression(left, leftPrecedenceRequirement,
-                          newInForInit: inForInit,
-                          newAtStatementBegin: atStatementBegin);
-
-    if (op == "in" || op == "instanceof") {
-      // There are cases where the space is not required but without further
-      // analysis we cannot know.
-      out(" ");
-      out(op);
-      out(" ");
-    } else {
-      if (leftSpace) spaceOut();
-      out(op);
-      spaceOut();
-    }
-    visitNestedExpression(right, rightPrecedenceRequirement,
-                          newInForInit: inForInit,
-                          newAtStatementBegin: false);
-  }
-
-  visitPrefix(Prefix unary) {
-    String op = unary.op;
-    switch (op) {
-      case "delete":
-      case "void":
-      case "typeof":
-        // There are cases where the space is not required but without further
-        // analysis we cannot know.
-        out(op);
-        out(" ");
-        break;
-      case "+":
-      case "++":
-        if (lastCharCode == charCodes.$PLUS) out(" ");
-        out(op);
-        break;
-      case "-":
-      case "--":
-        if (lastCharCode == charCodes.$MINUS) out(" ");
-        out(op);
-        break;
-      default:
-        out(op);
-    }
-    visitNestedExpression(unary.argument, unary.precedenceLevel,
-                          newInForInit: inForInit, newAtStatementBegin: false);
-  }
-
-  visitSpread(Spread unary) => visitPrefix(unary);
-
-  visitYield(Yield yield) {
-    out(yield.star ? "yield*" : "yield");
-    if (yield.value == null) return;
-    out(" ");
-    visitNestedExpression(yield.value, yield.precedenceLevel,
-        newInForInit: inForInit, newAtStatementBegin: false);
-  }
-
-  visitPostfix(Postfix postfix) {
-    visitNestedExpression(postfix.argument, LEFT_HAND_SIDE,
-                          newInForInit: inForInit,
-                          newAtStatementBegin: atStatementBegin);
-    out(postfix.op);
-  }
-
-  visitThis(This node) {
-    out("this");
-  }
-
-  visitSuper(Super node) {
-    out("super");
-  }
-
-  visitIdentifier(Identifier node) {
-    out(localNamer.getName(node));
-    outTypeAnnotation(node.type);
-  }
-
-  visitRestParameter(RestParameter node) {
-    out('...');
-    visitIdentifier(node.parameter);
-  }
-
-  bool isDigit(int charCode) {
-    return charCodes.$0 <= charCode && charCode <= charCodes.$9;
-  }
-
-  bool isValidJavaScriptId(String field) {
-    if (field.length < 3) return false;
-    // Ignore the leading and trailing string-delimiter.
-    for (int i = 1; i < field.length - 1; i++) {
-      // TODO(floitsch): allow more characters.
-      int charCode = field.codeUnitAt(i);
-      if (!(charCodes.$a <= charCode && charCode <= charCodes.$z ||
-            charCodes.$A <= charCode && charCode <= charCodes.$Z ||
-            charCode == charCodes.$$ ||
-            charCode == charCodes.$_ ||
-            i != 1 && isDigit(charCode))) {
-        return false;
-      }
-    }
-
-    // TODO(floitsch): normally we should also check that the field is not a
-    // reserved word.  We don't generate fields with reserved word names except
-    // for 'super'.
-    return options.allowKeywordsInProperties || field != '"super"';
-  }
-
-  visitAccess(PropertyAccess access) {
-    // Normally we can omit parens on the receiver if it is a Call, even though
-    // Call expressions have lower precedence. However this optimization doesn't
-    // work inside New expressions:
-    //
-    //     new obj.foo().bar()
-    //
-    // This will be parsed as:
-    //
-    //     (new obj.foo()).bar()
-    //
-    // Which is incorrect. So we must have parenthesis in this case:
-    //
-    //     new (obj.foo()).bar()
-    //
-    int precedence = inNewTarget ? ACCESS : CALL;
-
-    visitNestedExpression(access.receiver, precedence,
-                          newInForInit: inForInit,
-                          newAtStatementBegin: atStatementBegin);
-    propertyNameOut(access.selector, inAccess: true);
-  }
-
-  visitNamedFunction(NamedFunction namedFunction) {
-    functionOut(namedFunction.function, namedFunction.name);
-  }
-
-  visitFun(Fun fun) {
-    functionOut(fun, null);
-  }
-
-  visitArrowFun(ArrowFun fun) {
-    localNamer.enterScope(fun);
-    if (fun.params.length == 1 &&
-        (fun.params.single.type == null || !options.emitTypes)) {
-      visitNestedExpression(fun.params.single, SPREAD,
-          newInForInit: false, newAtStatementBegin: false);
-    } else {
-      out("(");
-      visitCommaSeparated(fun.params, SPREAD,
-          newInForInit: false, newAtStatementBegin: false);
-      out(")");
-    }
-    outTypeAnnotation(fun.returnType);
-    spaceOut();
-    out("=>");
-    if (fun.body is Expression) {
-      spaceOut();
-      // Object initializers require parenthesis to disambiguate
-      // AssignmentExpression from FunctionBody. See:
-      // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-arrow-function-definitions
-      var needsParen = fun.body is ObjectInitializer;
-      if (needsParen) out("(");
-      visitNestedExpression(fun.body, ASSIGNMENT,
-          newInForInit: false, newAtStatementBegin: false);
-      if (needsParen) out(")");
-    } else {
-      blockBody(fun.body, needsSeparation: false, needsNewline: false);
-    }
-    localNamer.leaveScope();
-  }
-
-  visitLiteralBool(LiteralBool node) {
-    out(node.value ? "true" : "false");
-  }
-
-  visitLiteralString(LiteralString node) {
-    out(node.value);
-  }
-
-  visitLiteralNumber(LiteralNumber node) {
-    int charCode = node.value.codeUnitAt(0);
-    if (charCode == charCodes.$MINUS && lastCharCode == charCodes.$MINUS) {
-      out(" ");
-    }
-    out(node.value);
-  }
-
-  visitLiteralNull(LiteralNull node) {
-    out("null");
-  }
-
-  visitArrayInitializer(ArrayInitializer node) {
-    out("[");
-    indentMore();
-    var multiline = node.multiline;
-    List<Expression> elements = node.elements;
-    for (int i = 0; i < elements.length; i++) {
-      Expression element = elements[i];
-      if (element is ArrayHole) {
-        // Note that array holes must have a trailing "," even if they are
-        // in last position. Otherwise `[,]` (having length 1) would become
-        // equal to `[]` (the empty array)
-        // and [1,,] (array with 1 and a hole) would become [1,] = [1].
-        out(",");
-        continue;
-      }
-      if (i != 0 && !multiline) spaceOut();
-      if (multiline) {
-        forceLine();
-        indent();
-      }
-      visitNestedExpression(element, ASSIGNMENT,
-                            newInForInit: false, newAtStatementBegin: false);
-      // We can skip the trailing "," for the last element (since it's not
-      // an array hole).
-      if (i != elements.length - 1) out(",");
-    }
-    indentLess();
-    if (multiline) {
-      lineOut();
-      indent();
-    }
-    out("]");
-  }
-
-  visitArrayHole(ArrayHole node) {
-    throw "Unreachable";
-  }
-
-  visitObjectInitializer(ObjectInitializer node) {
-    List<Property> properties = node.properties;
-    out("{");
-    indentMore();
-
-    var multiline = node.multiline;
-    for (int i = 0; i < properties.length; i++) {
-      if (i != 0) {
-        out(",");
-        if (!multiline) spaceOut();
-      }
-      if (multiline) {
-        forceLine();
-        indent();
-      }
-      visit(properties[i]);
-    }
-    indentLess();
-    if (multiline) {
-      lineOut();
-      indent();
-    }
-    out("}");
-  }
-
-  visitProperty(Property node) {
-    propertyNameOut(node.name);
-    out(":");
-    spaceOut();
-    visitNestedExpression(node.value, ASSIGNMENT,
-                          newInForInit: false, newAtStatementBegin: false);
-  }
-
-  visitRegExpLiteral(RegExpLiteral node) {
-    out(node.pattern);
-  }
-
-  visitTemplateString(TemplateString node) {
-    out('`');
-    for (var element in node.elements) {
-      if (element is String) {
-        out(element);
-      } else {
-        out(r'${');
-        visit(element);
-        out('}');
-      }
-    }
-    out('`');
-  }
-
-  visitTaggedTemplate(TaggedTemplate node) {
-    visit(node.tag);
-    visit(node.template);
-  }
-
-  visitClassDeclaration(ClassDeclaration node) {
-    indent();
-    visit(node.classExpr);
-    lineOut();
-  }
-
-  void outTypeParams(Iterable<Identifier> typeParams) {
-    if (typeParams != null && options.emitTypes && typeParams.isNotEmpty) {
-      out("<");
-      var first = true;
-      for (var typeParam in typeParams) {
-        if (!first) out(", ");
-        first = false;
-        visit(typeParam);
-      }
-      out(">");
-    }
-  }
-
-  visitClassExpression(ClassExpression node) {
-    out('class ');
-    visit(node.name);
-    outTypeParams(node.typeParams);
-    if (node.heritage != null) {
-      out(' extends ');
-      visit(node.heritage);
-    }
-    spaceOut();
-    if (node.methods.isNotEmpty) {
-      out('{');
-      lineOut();
-      indentMore();
-      if (options.emitTypes && node.fields != null) {
-        for (var field in node.fields) {
-          indent();
-          visit(field);
-          out(";");
-          lineOut();
-        }
-      }
-      for (var method in node.methods) {
-        indent();
-        visit(method);
-        lineOut();
-      }
-      indentLess();
-      indent();
-      out('}');
-    } else {
-      out('{}');
-    }
-  }
-
-  visitMethod(Method node) {
-    outClosureAnnotation(node);
-    if (node.isStatic) {
-      out('static ');
-    }
-    if (node.isGetter) {
-      out('get ');
-    } else if (node.isSetter) {
-      out('set ');
-    } else if (node.function.isGenerator) {
-      out('*');
-    }
-    propertyNameOut(node.name, inMethod: true);
-
-    var fun = node.function;
-    localNamer.enterScope(fun);
-    out("(");
-    if (fun.params != null) {
-      visitCommaSeparated(fun.params, SPREAD,
-          newInForInit: false, newAtStatementBegin: false);
-    }
-    out(")");
-    // TODO(jmesserly): async modifiers
-    if (fun.body.statements.isEmpty) {
-      spaceOut();
-      out("{}");
-    } else {
-      blockBody(fun.body, needsSeparation: false, needsNewline: false);
-    }
-    localNamer.leaveScope();
-  }
-
-  void outClosureAnnotation(Node node) {
-    if (node != null && node.closureAnnotation != null) {
-      String comment = node.closureAnnotation.toString(indentation);
-      if (comment.isNotEmpty) {
-        out(comment);
-        lineOut();
-        indent();
-      }
-    }
-  }
-
-  void propertyNameOut(Expression node, {bool inMethod: false,
-      bool inAccess: false}) {
-
-    if (node is LiteralNumber) {
-      LiteralNumber nameNumber = node;
-      if (inAccess) out('[');
-      out(nameNumber.value);
-      if (inAccess) out(']');
-    } else {
-      if (node is LiteralString) {
-        if (isValidJavaScriptId(node.value)) {
-          if (inAccess) out('.');
-          out(node.valueWithoutQuotes);
-        } else {
-          if (inMethod || inAccess) out("[");
-          out(node.value);
-          if (inMethod || inAccess) out("]");
-        }
-      } else {
-        // ComputedPropertyName
-        out("[");
-        visitNestedExpression(node, EXPRESSION,
-                              newInForInit: false, newAtStatementBegin: false);
-        out("]");
-      }
-    }
-  }
-
-  visitImportDeclaration(ImportDeclaration node) {
-    indent();
-    out('import ');
-    if (node.defaultBinding != null) {
-      visit(node.defaultBinding);
-      if (node.namedImports != null) {
-        out(',');
-        spaceOut();
-      }
-    }
-    nameSpecifierListOut(node.namedImports);
-    fromClauseOut(node.from);
-    outSemicolonLn();
-  }
-
-  visitExportDeclaration(ExportDeclaration node) {
-    indent();
-    out('export ');
-    if (node.isDefault) out('default ');
-    // TODO(jmesserly): we need to avoid indent/newline if this is a statement.
-    visit(node.exported);
-    outSemicolonLn();
-  }
-
-  visitExportClause(ExportClause node) {
-    nameSpecifierListOut(node.exports);
-    fromClauseOut(node.from);
-  }
-
-  nameSpecifierListOut(List<NameSpecifier> names) {
-    if (names == null) return;
-
-    if (names.length == 1 && names[0].name == '*') {
-      visit(names[0]);
-      return;
-    }
-
-    out('{');
-    spaceOut();
-    for (int i = 0; i < names.length; i++) {
-      if (i != 0) {
-        out(',');
-        spaceOut();
-      }
-      visit(names[i]);
-    }
-    spaceOut();
-    out('}');
-  }
-
-  fromClauseOut(LiteralString from) {
-    if (from != null) {
-      out(' from');
-      spaceOut();
-      visit(from);
-    }
-  }
-
-  visitNameSpecifier(NameSpecifier node) {
-    out(node.name);
-    if (node.asName != null) {
-      out(' as ');
-      out(node.asName);
-    }
-  }
-
-  visitModule(Module node) {
-    visitAll(node.body);
-  }
-
-  visitLiteralExpression(LiteralExpression node) {
-    String template = node.template;
-    List<Expression> inputs = node.inputs;
-
-    List<String> parts = template.split('#');
-    int inputsLength = inputs == null ? 0 : inputs.length;
-    if (parts.length != inputsLength + 1) {
-      context.error('Wrong number of arguments for JS: $template');
-    }
-    // Code that uses JS must take care of operator precedences, and
-    // put parenthesis if needed.
-    out(parts[0]);
-    for (int i = 0; i < inputsLength; i++) {
-      visit(inputs[i]);
-      out(parts[i + 1]);
-    }
-  }
-
-  visitLiteralStatement(LiteralStatement node) {
-    outLn(node.code);
-  }
-
-  visitInterpolatedNode(InterpolatedNode node) {
-    out('#${node.nameOrPosition}');
-  }
-
-  visitInterpolatedExpression(InterpolatedExpression node) =>
-      visitInterpolatedNode(node);
-
-  visitInterpolatedLiteral(InterpolatedLiteral node) =>
-      visitInterpolatedNode(node);
-
-  visitInterpolatedParameter(InterpolatedParameter node) =>
-      visitInterpolatedNode(node);
-
-  visitInterpolatedSelector(InterpolatedSelector node) =>
-      visitInterpolatedNode(node);
-
-  visitInterpolatedMethod(InterpolatedMethod node) =>
-      visitInterpolatedNode(node);
-
-  visitInterpolatedIdentifier(InterpolatedIdentifier node) =>
-      visitInterpolatedNode(node);
-
-  visitInterpolatedStatement(InterpolatedStatement node) {
-    outLn('#${node.nameOrPosition}');
-  }
-
-  void visitComment(Comment node) {
-    if (shouldCompressOutput) return;
-    String comment = node.comment.trim();
-    if (comment.isEmpty) return;
-    for (var line in comment.split('\n')) {
-      if (comment.startsWith('//')) {
-        outIndentLn(line.trim());
-      } else {
-        outIndentLn('// ${line.trim()}');
-      }
-    }
-  }
-
-  void visitCommentExpression(CommentExpression node) {
-    if (shouldCompressOutput) return;
-    String comment = node.comment.trim();
-    if (comment.isEmpty) return;
-    if (comment.startsWith('/*')) {
-      out(comment);
-    } else {
-      out('/* $comment */');
-    }
-    visit(node.expression);
-  }
-
-  void visitAwait(Await node) {
-    out("await ");
-    visit(node.expression);
-  }
-
-  void outTypeAnnotation(TypeRef node) {
-    if (node == null || !options.emitTypes || node.isUnknown) return;
-
-    if (node is OptionalTypeRef) {
-      out("?: ");
-      visit(node.type);
-    } else {
-      out(": ");
-      visit(node);
-    }
-  }
-}
-
-// Collects all the var declarations in the function.  We need to do this in a
-// separate pass because JS vars are lifted to the top of the function.
-class VarCollector extends BaseVisitor {
-  bool nested;
-  final Set<String> vars;
-  final Set<String> params;
-
-  VarCollector() : nested = false,
-                   vars = new Set<String>(),
-                   params = new Set<String>();
-
-  void forEachVar(void fn(String v)) => vars.forEach(fn);
-  void forEachParam(void fn(String p)) => params.forEach(fn);
-
-  void collectVarsInFunction(FunctionExpression fun) {
-    if (!nested) {
-      nested = true;
-      if (fun.params != null) {
-        for (var param in fun.params) {
-          params.add(param.name);
-        }
-      }
-      fun.body.accept(this);
-      nested = false;
-    }
-  }
-
-  void visitFunctionDeclaration(FunctionDeclaration declaration) {
-    // Note that we don't bother collecting the name of the function.
-    collectVarsInFunction(declaration.function);
-  }
-
-  void visitNamedFunction(NamedFunction namedFunction) {
-    // Note that we don't bother collecting the name of the function.
-    collectVarsInFunction(namedFunction.function);
-  }
-
-  void visitMethod(Method declaration) {
-    collectVarsInFunction(declaration.function);
-  }
-
-  void visitFun(Fun fun) {
-    collectVarsInFunction(fun);
-  }
-
-  void visitArrowFun(ArrowFun fun) {
-    collectVarsInFunction(fun);
-  }
-
-  void visitClassExpression(ClassExpression node) {
-    // Note that we don't bother collecting the name of the class.
-    if (node.heritage != null) node.heritage.accept(this);
-    for (Method method in node.methods) method.accept(this);
-  }
-
-  void visitCatch(Catch node) {
-    declareVariable(node.declaration);
-    node.body.accept(this);
-  }
-
-  void visitVariableInitialization(VariableInitialization node) {
-    declareVariable(node.declaration);
-    if (node.value != null) node.value.accept(this);
-  }
-
-  void declareVariable(Identifier decl) {
-    if (decl.allowRename) vars.add(decl.name);
-  }
-}
-
-
-/**
- * Returns true, if the given node must be wrapped into braces when used
- * as then-statement in an [If] that has an else branch.
- */
-class DanglingElseVisitor extends BaseVisitor<bool> {
-  JavaScriptPrintingContext context;
-
-  DanglingElseVisitor(this.context);
-
-  bool visitProgram(Program node) => false;
-
-  bool visitNode(Node node) {
-    context.error("Forgot node: $node");
-    return null;
-  }
-
-  bool visitBlock(Block node) => false;
-  bool visitExpressionStatement(ExpressionStatement node) => false;
-  bool visitEmptyStatement(EmptyStatement node) => false;
-  bool visitIf(If node) {
-    if (!node.hasElse) return true;
-    return node.otherwise.accept(this);
-  }
-  bool visitFor(For node) => node.body.accept(this);
-  bool visitForIn(ForIn node) => node.body.accept(this);
-  bool visitForOf(ForOf node) => node.body.accept(this);
-  bool visitWhile(While node) => node.body.accept(this);
-  bool visitDo(Do node) => false;
-  bool visitContinue(Continue node) => false;
-  bool visitBreak(Break node) => false;
-  bool visitReturn(Return node) => false;
-  bool visitThrow(Throw node) => false;
-  bool visitTry(Try node) {
-    if (node.finallyPart != null) {
-      return node.finallyPart.accept(this);
-    } else {
-      return node.catchPart.accept(this);
-    }
-  }
-  bool visitCatch(Catch node) => node.body.accept(this);
-  bool visitSwitch(Switch node) => false;
-  bool visitCase(Case node) => false;
-  bool visitDefault(Default node) => false;
-  bool visitFunctionDeclaration(FunctionDeclaration node) => false;
-  bool visitLabeledStatement(LabeledStatement node)
-      => node.body.accept(this);
-  bool visitLiteralStatement(LiteralStatement node) => true;
-  bool visitClassDeclaration(ClassDeclaration node) => false;
-
-  bool visitExpression(Expression node) => false;
-}
-
-
-abstract class LocalNamer {
-  String getName(Identifier node);
-  void enterScope(FunctionExpression node);
-  void leaveScope();
-}
-
-
-class IdentityNamer implements LocalNamer {
-  String getName(Identifier node) => node.name;
-  void enterScope(FunctionExpression node) {}
-  void leaveScope() {}
-}
-
-
-class MinifyRenamer implements LocalNamer {
-  final List<Map<String, String>> maps = [];
-  final List<int> parameterNumberStack = [];
-  final List<int> variableNumberStack = [];
-  int parameterNumber = 0;
-  int variableNumber = 0;
-
-  void enterScope(FunctionExpression node) {
-    var vars = new VarCollector();
-    node.accept(vars);
-    maps.add(new Map<String, String>());
-    variableNumberStack.add(variableNumber);
-    parameterNumberStack.add(parameterNumber);
-    vars.forEachVar(declareVariable);
-    vars.forEachParam(declareParameter);
-  }
-
-  void leaveScope() {
-    maps.removeLast();
-    variableNumber = variableNumberStack.removeLast();
-    parameterNumber = parameterNumberStack.removeLast();
-  }
-
-  String getName(Identifier node) {
-    String oldName = node.name;
-    // Go from inner scope to outer looking for mapping of name.
-    for (int i = maps.length - 1; i >= 0; i--) {
-      var map = maps[i];
-      var replacement = map[oldName];
-      if (replacement != null) return replacement;
-    }
-    return oldName;
-  }
-
-  static const LOWER_CASE_LETTERS = 26;
-  static const LETTERS = LOWER_CASE_LETTERS;
-  static const DIGITS = 10;
-
-  static int nthLetter(int n) {
-    return (n < LOWER_CASE_LETTERS) ?
-           charCodes.$a + n :
-           charCodes.$A + n - LOWER_CASE_LETTERS;
-  }
-
-  // Parameters go from a to z and variables go from z to a.  This makes each
-  // argument list and each top-of-function var declaration look similar and
-  // helps gzip compress the file.  If we have more than 26 arguments and
-  // variables then we meet somewhere in the middle of the alphabet.  After
-  // that we give up trying to be nice to the compression algorithm and just
-  // use the same namespace for arguments and variables, starting with A, and
-  // moving on to a0, a1, etc.
-  String declareVariable(String oldName) {
-    if (avoidRenaming(oldName)) return oldName;
-    var newName;
-    if (variableNumber + parameterNumber < LOWER_CASE_LETTERS) {
-      // Variables start from z and go backwards, for better gzipability.
-      newName = getNameNumber(oldName, LOWER_CASE_LETTERS - 1 - variableNumber);
-    } else {
-      // After 26 variables and parameters we allocate them in the same order.
-      newName = getNameNumber(oldName, variableNumber + parameterNumber);
-    }
-    variableNumber++;
-    return newName;
-  }
-
-  String declareParameter(String oldName) {
-    if (avoidRenaming(oldName)) return oldName;
-    var newName;
-    if (variableNumber + parameterNumber < LOWER_CASE_LETTERS) {
-      newName = getNameNumber(oldName, parameterNumber);
-    } else {
-      newName = getNameNumber(oldName, variableNumber + parameterNumber);
-    }
-    parameterNumber++;
-    return newName;
-  }
-
-  bool avoidRenaming(String oldName) {
-    // Variables of this $form$ are used in pattern matching the message of JS
-    // exceptions, so should not be renamed.
-    // TODO(sra): Introduce a way for indicating in the JS text which variables
-    // should not be renamed.
-    return oldName.startsWith(r'$') && oldName.endsWith(r'$');
-  }
-
-  String getNameNumber(String oldName, int n) {
-    if (maps.isEmpty) return oldName;
-
-    String newName;
-    if (n < LETTERS) {
-      // Start naming variables a, b, c, ..., z, A, B, C, ..., Z.
-      newName = new String.fromCharCodes([nthLetter(n)]);
-    } else {
-      // Then name variables a0, a1, a2, ..., a9, b0, b1, ..., Z9, aa0, aa1, ...
-      // For all functions with fewer than 500 locals this is just as compact
-      // as using aa, ab, etc. but avoids clashes with keywords.
-      n -= LETTERS;
-      int digit = n % DIGITS;
-      n ~/= DIGITS;
-      int alphaChars = 1;
-      int nameSpaceSize = LETTERS;
-      // Find out whether we should use the 1-character namespace (size 52), the
-      // 2-character namespace (size 52*52), etc.
-      while (n >= nameSpaceSize) {
-        n -= nameSpaceSize;
-        alphaChars++;
-        nameSpaceSize *= LETTERS;
-      }
-      var codes = <int>[];
-      for (var i = 0; i < alphaChars; i++) {
-        nameSpaceSize ~/= LETTERS;
-        codes.add(nthLetter((n ~/ nameSpaceSize) % LETTERS));
-      }
-      codes.add(charCodes.$0 + digit);
-      newName = new String.fromCharCodes(codes);
-    }
-    assert(new RegExp(r'[a-zA-Z][a-zA-Z0-9]*').hasMatch(newName));
-    maps.last[oldName] = newName;
-    return newName;
-  }
-}
-
-/// Like [BaseVisitor], but calls [declare] for [Identifier] declarations, and
-/// [visitIdentifier] otherwise.
-abstract class VariableDeclarationVisitor<T> extends BaseVisitor<T> {
-  declare(Identifier node);
-
-  visitFunctionExpression(FunctionExpression node) {
-    node.params.forEach(_scanVariableBinding);
-    node.body.accept(this);
-  }
-
-  _scanVariableBinding(VariableBinding d) {
-    if (d is Identifier) declare(d);
-    else d.accept(this);
-  }
-
-  visitRestParameter(RestParameter node) {
-    _scanVariableBinding(node.parameter);
-    super.visitRestParameter(node);
-  }
-
-  visitDestructuredVariable(DestructuredVariable node) {
-    var name = node.name;
-    if (name is Identifier) _scanVariableBinding(name);
-    super.visitDestructuredVariable(node);
-  }
-
-  visitSimpleBindingPattern(SimpleBindingPattern node) {
-    _scanVariableBinding(node.name);
-    super.visitSimpleBindingPattern(node);
-  }
-
-  visitVariableInitialization(VariableInitialization node) {
-    _scanVariableBinding(node.declaration);
-    if (node.value != null) node.value.accept(this);
-  }
-
-  visitCatch(Catch node) {
-    declare(node.declaration);
-    node.body.accept(this);
-  }
-
-  visitFunctionDeclaration(FunctionDeclaration node) {
-    declare(node.name);
-    node.function.accept(this);
-  }
-
-  visitNamedFunction(NamedFunction node) {
-    declare(node.name);
-    node.function.accept(this);
-  }
-
-  visitClassExpression(ClassExpression node) {
-    declare(node.name);
-    if (node.heritage != null) node.heritage.accept(this);
-    for (Method element in node.methods) element.accept(this);
-  }
-}