Enhance dart:js interop in a backwards compatible manner. List objects can now be passed back and f…

sdk/lib/js/dartium/js_dartium.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Support for interoperating with JavaScript.
  * 
  * This library provides access to JavaScript objects from Dart, allowing
  * Dart code to get and set properties, and call methods of JavaScript objects
  * and invoke JavaScript functions. The library takes care of converting
@@ skipping 71 matching lines @@
  *     var jsMap = new JsObject.jsify({'a': 1, 'b': 2});
  * 
  * This expression creates a JavaScript array:
  *
  *     var jsArray = new JsObject.jsify([1, 2, 3]);
  */
 library dart.js;
 
 import 'dart:collection' show ListMixin;
 import 'dart:nativewrappers';
+import 'dart:math' as math;
+import 'dart:mirrors' as mirrors;
+
+// TODO(jacobr): if we care about unchecked mode in Dartium we need to set this
+// to false in unchecked mode.

[vsm, 2015/06/22 22:27:48]

That is still the default mode (unchecked).

[Jacob, 2015/06/24 22:21:58]

switched this to an actual ugly test for checked mode.

+final bool _CHECK_JS_INVOCATIONS = true;
+
+final _allowedMethods = new Map<Symbol, _DeclarationSet>();
+final _allowedGetters = new Map<Symbol, _DeclarationSet>();
+final _allowedSetters = new Map<Symbol, _DeclarationSet>();
+
+final Set<Type> _jsInterfaceTypes = new Set<Type>();

[vsm, 2015/06/22 22:27:48]

could drop the lhs type here.

[Jacob, 2015/06/24 22:21:58]

Done.

+Iterable<Type> get jsInterfaceTypes => _jsInterfaceTypes.toList();

[vsm, 2015/06/22 22:27:48]

Do you need toList?  I think a Set is an Iterable already.

[Jacob, 2015/06/24 22:21:58]

Done.

+
+class _DeclarationSet {
+  _DeclarationSet() : _members = <mirrors.DeclarationMirror>[];
+
+  bool _checkType(obj, type) {

[vsm, 2015/06/22 22:27:48]

This could be static.  Is type a Type or a TypeMirror?  Annotate?

[Jacob, 2015/06/24 22:21:58]

Done.

+    if (obj == null) return true;
+    return mirrors.reflectType(obj.runtimeType).isSubtypeOf(type);
+  }
+
+  bool _checkReturnType(value) {

[vsm, 2015/06/22 22:27:48]

Comment on what this function does?

[Jacob, 2015/06/24 22:21:58]

Done.

+    if (value == null) return true;
+    var valueMirror = mirrors.reflectType(value.runtimeType);
+    for (var member in _members) {
+      if (member is mirrors.VariableMirror || member.isGetter) {
+        // TODO(jacobr): actually check return types for getters that return
+        // function types.
+        return true;
+      } else {
+        if (valueMirror.isSubtypeOf(member.returnType)) return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Check whether the [invocation] is consistent with the [member] mirror.
+   */
+  bool _checkDeclaration(
+      Invocation invocation, mirrors.DeclarationMirror member) {
+    if (member is mirrors.VariableMirror || member.isGetter) {
+      // TODO(jacobr): actually check method types against the function type returned

[vsm, 2015/06/22 22:27:48]

line len

[Jacob, 2015/06/24 22:21:58]

Done.

+      // by the getter or field.
+      return true;
+    }
+    var parameters = member.parameters;
+    var positionalArguments = invocation.positionalArguments;
+    // Too many arguments
+    if (parameters.length < positionalArguments.length) return false;
+    // Too few required arguments.
+    if (parameters.length > positionalArguments.length &&
+        !parameters[positionalArguments.length].isOptional) return false;
+    var endPositional = math.min(parameters.length, positionalArguments.length);

[vsm, 2015/06/22 22:27:48]

I don't think you need math.min - you already compared in line 142.

[Jacob, 2015/06/24 22:21:58]

Done.

+    for (var i = 0; i < endPositional; i++) {
+      if (parameters[i].isNamed) {
+        // Not enough positional arguments.
+        return false;
+      }
+      if (!_checkType(
+          invocation.positionalArguments[i], parameters[i].type)) return false;
+    }
+    if (invocation.namedArguments.isNotEmpty) {
+      var startPositional;

[vsm, 2015/06/22 22:27:48]

startNamed?

[Jacob, 2015/06/24 22:21:58]

Done.

+      for (startPositional = parameters.length - 1;
+          startPositional >= 0;
+          startPositional--) {
+        if (!parameters[startPositional].isNamed) break;
+      }
+      startPositional++;
+
+      for (var name in invocation.namedArguments.keys) {
+        bool match = false;
+        for (var j = startPositional; j < parameters.length; j++) {

[vsm, 2015/06/22 22:27:48]

Perhaps worth making a HashSet to avoid the n^2?  We have APIs with a bunch of
named params.  Or inverting this, walking over parameters, querying invocation,
and making sure you match invocation.namedArguments.size keys?

[Jacob, 2015/06/24 22:21:58]

These are just named parameters in JS implemented API which I don't expect there
will be that many. However, added A TODO with your suggestion. If many methods
have >10 named arguments I expect there will be a significant performance
difference. At one point micro benchmarks for C++ STL showed that for <20,
vector was actually faster than set. No idea what it is for Dart but I still
expect for typical <=3 named parameters methods it won't matter that much.

+          var p = parameters[j];
+          if (p.simpleName == name) {
+            if (!_checkType(invocation.namedArguments[name],
+                parameters[j].type)) return false;
+            match = true;
+            break;
+          }
+        }
+        if (match == false) return false;
+      }
+    }
+    return true;
+  }
+
+  bool checkInvocation(Invocation invocation) {
+    for (var member in _members) {

[vsm, 2015/06/22 22:27:48]

Don't you need a name match?  And, if so, _members could be a map keyed by name?

[Jacob, 2015/06/24 22:21:58]

This is within a DeclarationSet which is the set of all methods with the same
name. Added a top level class comment.

+      if (_checkDeclaration(invocation, member)) return true;
+    }
+    return false;
+  }
+
+  void add(mirrors.DeclarationMirror mirror) {
+    _members.add(mirror);
+  }
+
+  final List<mirrors.DeclarationMirror> _members;
+}
+
+/**
+ * Temporary method that we hope to remove at some point. This method should
+ * generally only be called by machine generated code.
+ */
+void registerJsInterfaces(List<Type> classes) {
+  if (_finalized == true) {
+    throw 'JSInterop class registration already finalized';
+  }
+  Map<Symbol, List<mirrors.DeclarationMirror>> allMembers;

[vsm, 2015/06/22 22:27:48]

Is this used?

[Jacob, 2015/06/24 22:21:58]

Done.

+  for (Type type in classes) {
+    if (!_jsInterfaceTypes.add(type)) continue; // Already registered.
+    mirrors.ClassMirror typeMirror = mirrors.reflectType(type);
+    typeMirror.declarations.forEach((symbol, declaration) {
+      if (declaration is mirrors.MethodMirror ||
+          declaration is mirrors.VariableMirror && !declaration.isStatic) {
+        bool treatAsGetter = false;
+        bool treatAsSetter = false;
+        if (declaration is mirrors.VariableMirror) {
+          treatAsGetter = true;
+          if (!declaration.isConst && !declaration.isFinal) treatAsSetter =

[vsm, 2015/06/22 22:27:48]

braces for multiline if

[Jacob, 2015/06/24 22:21:58]

Done.

+              true;
+        } else {
+          if (declaration.isGetter) {
+            _allowedGetters
+                .putIfAbsent(symbol, () => new _DeclarationSet())
+                .add(declaration);
+            _allowedMethods

[vsm, 2015/06/22 22:27:48]

This looks redundant with the code below also updating these sets.

[Jacob, 2015/06/24 22:21:58]

Done.

+                .putIfAbsent(symbol, () => new _DeclarationSet())
+                .add(declaration);
+            treatAsGetter = true;
+          } else if (declaration.isSetter) {
+            treatAsSetter = true;
+          } else if (!declaration.isConstructor) {
+            _allowedMethods
+                .putIfAbsent(symbol, () => new _DeclarationSet())
+                .add(declaration);
+          }
+        }
+        if (treatAsGetter) {
+          _allowedGetters
+              .putIfAbsent(symbol, () => new _DeclarationSet())
+              .add(declaration);
+          _allowedMethods
+              .putIfAbsent(symbol, () => new _DeclarationSet())
+              .add(declaration);
+        }
+        if (treatAsSetter) {
+          _allowedSetters
+              .putIfAbsent(symbol, () => new _DeclarationSet())
+              .add(declaration);
+        }
+      }
+    });
+  }
+}
+
+_finalizeJsInterfaces() native "Js_finalizeJsInterfaces";
+
+/**
+ * Generates a part file defining source code for JsObjectImpl and related
+ * classes. This calass is needed so that type checks for all registered JavaScript
+ * interop classes pass.
+ */
+String _generateJsObjectImplPart() {
+  Iterable<Type> types = jsInterfaceTypes;
+  var libraryPrefixes = new Map<mirrors.LibraryMirror, String>();
+  var prefixNames = new Set<String>();
+  var sb = new StringBuffer();
+
+  var implements = <String>[];
+  for (var type in types) {
+    mirrors.ClassMirror typeMirror = mirrors.reflectType(type);
+    mirrors.LibraryMirror libraryMirror = typeMirror.owner;
+    var prefixName;
+    if (libraryPrefixes.containsKey(libraryMirror)) {
+      prefixName = libraryPrefixes[libraryMirror];
+    } else {
+      var basePrefixName =
+          mirrors.MirrorSystem.getName(libraryMirror.simpleName);
+      basePrefixName = basePrefixName.replaceAll('.', '_');
+      if (basePrefixName.isEmpty) basePrefixName = "lib";
+      prefixName = basePrefixName;
+      var i = 1;
+      while (prefixNames.contains(prefixName)) {
+        prefixName = '$basePrefixName$i';
+        i++;
+      }
+      prefixNames.add(prefixName);
+      libraryPrefixes[libraryMirror] = prefixName;
+    }
+    implements.add(
+        '${prefixName}.${mirrors.MirrorSystem.getName(typeMirror.simpleName)}');
+  }
+  libraryPrefixes.forEach((libraryMirror, prefix) {
+    sb.writeln('import "${libraryMirror.uri}" as $prefix;');
+  });
+  var implementsClause =
+      implements.isEmpty ? "" : "implements ${implements.join(', ')}";
+  // TODO(jacobr): only certain classes need to be implemented by
+  // Function and Array.
+  sb.write('''
+class JsObjectImpl extends JsObject $implementsClause {
+  JsObjectImpl.internal() : super.internal();
+}
+
+class JsFunctionImpl extends JsFunction $implementsClause {
+  JsFunctionImpl.internal() : super.internal();
+}
+
+class JsArrayImpl<E> extends JsArray<E> $implementsClause {
+  JsArrayImpl.internal() : super.internal();
+}
+''');
+  return sb.toString();
+}
+
+// Start of block of helper methods facilitating emulating JavaScript Array
+// methods on Dart List objects passed to JavaScript via JS interop.
+// TODO(jacobr): match JS more closely.
+String _toStringJs(obj) => '$obj';
+
+// TODO(jacobr): this might not exactly match JS semantics but should be
+// adequate for now.
+int _toIntJs(obj) {
+  if (obj is int) return obj;
+  if (obj is num) return obj.toInt();
+  return num.parse('$obj'.trim(), (_) => 0).toInt();
+}
+
+// TODO(jacobr): this might not exactly match JS semantics but should be
+// adequate for now.
+num _toNumJs(obj) {
+  return obj is num ? obj : num.parse('$obj'.trim(), (_) => 0);
+}
+
+/// Match the behavior of setting List length in JavaScript with the exception
+/// that Dart does not distinguish undefined and null.
+_setListLength(List list, rawlen) {
+  num len = _toNumJs(rawlen);
+  if (len is! int || len < 0) {
+    throw new RangeError("Invalid array length");
+  }
+  if (len > list.length) {
+    _arrayExtend(list, len);
+  } else if (len < list.length) {
+    list.removeRange(len, list.length);
+  }
+  return rawlen;
+}
+
+// TODO(jacobr): should we really bother with this method instead of just
+// shallow copying to a JS array and calling the JavaScript join method?
+String _arrayJoin(List list, sep) {
+  if (sep == null) {
+    sep = ",";
+  }
+  return list.map((e) => e == null ? "" : e.toString()).join(sep.toString());
+}
+
+// TODO(jacobr): should we really bother with this method instead of just
+// shallow copying to a JS array and using the toString method?
+String _arrayToString(List list) => _arrayJoin(list, ",");
+
+int _arrayPush(List list, e) {
+  list.add(e);
+  return list.length;
+}
+
+_arrayPop(List list) {
+  if (list.length > 0) return list.removeLast();
+}
+
+// TODO(jacobr): would it be better to just copy input to a JS List
+// and call Array.concat?
+List _arrayConcat(List input, List args) {
+  var ret = new List.from(input);
+  for (var e in args) {
+    // TODO(jacobr): technically in ES6 we should use
+    // Symbol.isConcatSpreadable to determine whether call addAll. Once v8
+    // supports it, we can make all Dart classes implementing Iterable
+    // specify isConcatSpreadable and tweak this behavior to allow Iterable.
+    if (e is List) {
+      ret.addAll(e);
+    } else {
+      ret.add(e);
+    }
+  }
+  return ret;
+}
+
+List _arraySplice(List input, List args) {
+  int start = 0;
+  if (args.length > 0) {
+    var rawStart = _toIntJs(args[0]);
+    if (rawStart < 0) {
+      start = math.max(0, input.length - rawStart);
+    } else {
+      start = math.min(input.length, rawStart);
+    }
+  }
+  var end = start;
+  if (args.length > 1) {
+    var rawDeleteCount = _toIntJs(args[1]);
+    if (rawDeleteCount < 0) rawDeleteCount = 0;
+    end = math.min(input.length, start + rawDeleteCount);
+  }
+  var replacement = [];
+  var removedElements = input.getRange(start, end).toList();
+  if (args.length > 2) {
+    replacement = args.getRange(2, args.length);
+  }
+  input.replaceRange(start, end, replacement);
+  return removedElements;
+}
+
+List _arrayReverse(List l) {
+  for (var i = 0, j = l.length - 1; i < j; i++, j--) {
+    var tmp = l[i];
+    l[i] = l[j];
+    l[j] = tmp;
+  }
+  return l;
+}
+
+_arrayShift(List l) {
+  if (l.isEmpty) return null; // Technically we should return undefined.
+  return l.removeAt(0);
+}
+
+int _arrayUnshift(List l, List args) {
+  l.insertAll(0, args);
+  return l.length;
+}
+
+_arrayExtend(List l, int newLength) {
+  for (var i = l.length; i < newLength; i++) {
+    // TODO(jacobr): we'd really like to add undefined to better match
+    // JavaScript semantics.
+    l.add(null);
+  }
+}
+
+List _arraySort(List l, rawCompare) {
+  // TODO(jacobr): alternately we could just copy the Array to JavaScript,
+  // invoke the JS sort method and then copy the result back to Dart.
+  Comparator compare;
+  if (rawCompare == null) {
+    compare = (a, b) => _toStringJs(a).compareTo(_toStringJs(b));
+  } else if (rawCompare is JsFunction) {
+    compare = (a, b) => rawCompare.apply([a, b]);
+  } else {
+    compare = rawCompare;
+  }
+  l.sort(compare);
+  return l;
+}
+// End of block of helper methods to emulate JavaScript Array methods on Dart List.
+
+/**
+ * Can be called to provide a predictable point where no more JS interfaces can
+ * be added. Creating an instance of JsObject will also automatically trigger
+ * all JsObjects to be finalized.
+ */
+void finalizeJsInterfaces() {
+  if (_finalized == true) {
+    throw 'JSInterop class registration already finalized';
+  }
+  _finalizeJsInterfaces();
+}
 
 JsObject _cachedContext;
 
 JsObject get _context native "Js_context_Callback";
 
+bool get _finalized native "Js_interfacesFinalized_Callback";
+
 JsObject get context {
   if (_cachedContext == null) {
     _cachedContext = _context;
   }
   return _cachedContext;
 }
 
 /**
  * Proxies a JavaScript object to Dart.
  *
  * The properties of the JavaScript object are accessible via the `[]` and
  * `[]=` operators. Methods are callable via [callMethod].
  */
 class JsObject extends NativeFieldWrapperClass2 {
   JsObject.internal();
 
   /**
    * Constructs a new JavaScript object from [constructor] and returns a proxy
    * to it.
    */
-  factory JsObject(JsFunction constructor, [List arguments]) => _create(constructor, arguments);
+  factory JsObject(JsFunction constructor, [List arguments]) =>
+      _create(constructor, arguments);
 
-  static JsObject _create(JsFunction constructor, arguments) native "JsObject_constructorCallback";
+  static JsObject _create(
+      JsFunction constructor, arguments) native "JsObject_constructorCallback";
+
+  _buildArgs(Invocation invocation) {
+    if (invocation.namedArguments.isEmpty) {
+      return invocation.positionalArguments;
+    } else {
+      var varArgs = new Map<String, Object>();
+      invocation.namedArguments.forEach((symbol, val) {
+        varArgs[mirrors.MirrorSystem.getName(symbol)] = val;
+      });
+      return invocation.positionalArguments.toList()
+        ..add(new JsObject.jsify(varArgs));
+    }
+  }
 
   /**
    * Constructs a [JsObject] that proxies a native Dart object; _for expert use
    * only_.
    *
    * Use this constructor only if you wish to get access to JavaScript
    * properties attached to a browser host object, such as a Node or Blob, that
    * is normally automatically converted into a native Dart object.
    * 
    * An exception will be thrown if [object] either is `null` or has the type
    * `bool`, `num`, or `String`.
    */
   factory JsObject.fromBrowserObject(object) {
     if (object is num || object is String || object is bool || object == null) {
-      throw new ArgumentError(
-        "object cannot be a num, string, bool, or null");
+      throw new ArgumentError("object cannot be a num, string, bool, or null");
     }
     return _fromBrowserObject(object);
   }
 
   /**
    * Recursively converts a JSON-like collection of Dart objects to a
    * collection of JavaScript objects and returns a [JsObject] proxy to it.
    *
    * [object] must be a [Map] or [Iterable], the contents of which are also
    * converted. Maps and Iterables are copied to a new JavaScript object.
    * Primitives and other transferrable values are directly converted to their
    * JavaScript type, and all other objects are proxied.
    */
   factory JsObject.jsify(object) {
     if ((object is! Map) && (object is! Iterable)) {
       throw new ArgumentError("object must be a Map or Iterable");
     }
     return _jsify(object);
   }
 
   static JsObject _jsify(object) native "JsObject_jsify";
 
-  static JsObject _fromBrowserObject(object) native "JsObject_fromBrowserObject";
+  static JsObject _fromBrowserObject(
+      object) native "JsObject_fromBrowserObject";
 
   /**
    * Returns the value associated with [property] from the proxied JavaScript
    * object.
    *
    * The type of [property] must be either [String] or [num].
    */
-  operator[](property) native "JsObject_[]";
+  operator [](property) native "JsObject_[]";
 
   /**
    * Sets the value associated with [property] on the proxied JavaScript
    * object.
    *
    * The type of [property] must be either [String] or [num].
    */
-  operator[]=(property, value) native "JsObject_[]=";
+  operator []=(property, value) native "JsObject_[]=";
 
   int get hashCode native "JsObject_hashCode";
 
-  operator==(other) => other is JsObject && _identityEquality(this, other);
+  operator ==(other) => other is JsObject && _identityEquality(this, other);
 
-  static bool _identityEquality(JsObject a, JsObject b) native "JsObject_identityEquality";
+  static bool _identityEquality(
+      JsObject a, JsObject b) native "JsObject_identityEquality";
 
   /**
    * Returns `true` if the JavaScript object contains the specified property
    * either directly or though its prototype chain.
    *
    * This is the equivalent of the `in` operator in JavaScript.
    */
   bool hasProperty(String property) native "JsObject_hasProperty";
 
   /**
    * Removes [property] from the JavaScript object.
    *
    * This is the equivalent of the `delete` operator in JavaScript.
    */
   void deleteProperty(String property) native "JsObject_deleteProperty";
 
   /**
    * Returns `true` if the JavaScript object has [type] in its prototype chain.
    *
    * This is the equivalent of the `instanceof` operator in JavaScript.
    */
   bool instanceof(JsFunction type) native "JsObject_instanceof";
 
   /**
    * Returns the result of the JavaScript objects `toString` method.
    */
   String toString() {
     try {
       return _toString();
-    } catch(e) {
+    } catch (e) {
       return super.toString();
     }
   }
 
   String _toString() native "JsObject_toString";
 
   /**
    * Calls [method] on the JavaScript object with the arguments [args] and
    * returns the result.
    *
    * The type of [method] must be either [String] or [num].
    */
   callMethod(String method, [List args]) {
     try {
       return _callMethod(method, args);
-    } catch(e) {
+    } catch (e) {
       if (hasProperty(method)) {
         rethrow;
       } else {
         throw new NoSuchMethodError(this, new Symbol(method), args, null);
       }
     }
   }
 
+  noSuchMethod(Invocation invocation) {
+    throwError() {
+      throw new NoSuchMethodError(this, invocation.memberName,
+          invocation.positionalArguments, invocation.namedArguments);
+    }
+
+    String name = mirrors.MirrorSystem.getName(invocation.memberName);
+    if (invocation.isGetter) {
+      if (_CHECK_JS_INVOCATIONS) {
+        var matches = _allowedGetters[invocation.memberName];
+        if (matches == null &&
+            !_allowedMethods.containsKey(invocation.memberName)) {
+          throwError();
+        }
+        var ret = this[name];
+        if (matches != null && matches._checkReturnType(ret)) return ret;
+        if (ret is Function ||
+            (ret is JsFunction /* shouldn't be needed in the future*/) &&
+                _allowedMethods.containsKey(
+                    invocation.memberName)) return ret; // Warning: we have not bound "this"... we could type check on the Function but that is of little value in Dart.
+        throwError();
+      } else {
+        // TODO(jacobr): should we throw if the JavaScript object doesn't have the property?
+        return this[name];
+      }
+    } else if (invocation.isSetter) {
+      if (_CHECK_JS_INVOCATIONS) {
+        var matches = _allowedSetters[invocation.memberName];
+        if (matches == null ||
+            !matches.checkInvocation(invocation)) throwError();
+      }
+      assert(name.endsWith("="));
+      name = name.substring(0, name.length - 1);
+      return this[name] = invocation.positionalArguments.first;
+    } else {
+      // TODO(jacobr): also allow calling getters that look like functions.
+      var matches;
+      if (_CHECK_JS_INVOCATIONS) {
+        matches = _allowedMethods[invocation.memberName];
+        if (matches == null ||
+            !matches.checkInvocation(invocation)) throwError();
+      }
+      var ret = this.callMethod(name, _buildArgs(invocation));
+      if (_CHECK_JS_INVOCATIONS) {
+        if (!matches._checkReturnType(ret)) throwError();
+      }
+      return ret;
+    }
+  }
+
   _callMethod(String name, List args) native "JsObject_callMethod";
 }
 
 /**
  * Proxies a JavaScript Function object.
  */
-class JsFunction extends JsObject {
+class JsFunction extends JsObject implements Function {
   JsFunction.internal() : super.internal();
 
   /**
    * Returns a [JsFunction] that captures its 'this' binding and calls [f]
    * with the value of this passed as the first argument.
    */
   factory JsFunction.withThis(Function f) => _withThis(f);
 
   /**
    * Invokes the JavaScript function with arguments [args]. If [thisArg] is
    * supplied it is the value of `this` for the invocation.
    */
   dynamic apply(List args, {thisArg}) native "JsFunction_apply";
 
+  noSuchMethod(Invocation invocation) {
+    if (invocation.isMethod && invocation.memberName == #call) {
+      return apply(_buildArgs(invocation));
+    }
+    return super.noSuchMethod(invocation);
+  }
+
   /**
    * Internal only version of apply which uses debugger proxies of Dart objects
    * rather than opaque handles. This method is private because it cannot be
    * efficiently implemented in Dart2Js so should only be used by internal
    * tools.
    */
-  _applyDebuggerOnly(List args, {thisArg}) native "JsFunction_applyDebuggerOnly";
+  _applyDebuggerOnly(List args,
+      {thisArg}) native "JsFunction_applyDebuggerOnly";
 
   static JsFunction _withThis(Function f) native "JsFunction_withThis";
 }
 
 /**
  * A [List] proxying a JavaScript Array.
  */
 class JsArray<E> extends JsObject with ListMixin<E> {
+  JsArray.internal() : super.internal();
 
   factory JsArray() => _newJsArray();
 
   static JsArray _newJsArray() native "JsArray_newJsArray";
 
-  factory JsArray.from(Iterable<E> other) => _newJsArrayFromSafeList(new List.from(other));
+  factory JsArray.from(Iterable<E> other) =>
+      _newJsArrayFromSafeList(new List.from(other));
 
-  static JsArray _newJsArrayFromSafeList(List list) native "JsArray_newJsArrayFromSafeList";
+  static JsArray _newJsArrayFromSafeList(
+      List list) native "JsArray_newJsArrayFromSafeList";
 
   _checkIndex(int index, {bool insert: false}) {
     int length = insert ? this.length + 1 : this.length;
     if (index is int && (index < 0 || index >= length)) {
       throw new RangeError.range(index, 0, length);
     }
   }
 
   _checkRange(int start, int end) {
     int cachedLength = this.length;
     if (start < 0 || start > cachedLength) {
       throw new RangeError.range(start, 0, cachedLength);
     }
     if (end < start || end > cachedLength) {
       throw new RangeError.range(end, start, cachedLength);
     }
   }
 
   // Methods required by ListMixin
 
   E operator [](index) {
     if (index is int) {
       _checkIndex(index);
     }
     return super[index];
   }
 
   void operator []=(index, E value) {
-    if(index is int) {
+    if (index is int) {
       _checkIndex(index);
     }
     super[index] = value;
   }
 
   int get length native "JsArray_length";
 
-  void set length(int length) { super['length'] = length; }
+  void set length(int length) {
+    super['length'] = length;
+  }
 
   // Methods overriden for better performance
 
   void add(E value) {
     callMethod('push', [value]);
   }
 
   void addAll(Iterable<E> iterable) {
     // TODO(jacobr): this can be optimized slightly.
     callMethod('push', new List.from(iterable));
   }
 
   void insert(int index, E element) {
-    _checkIndex(index, insert:true);
+    _checkIndex(index, insert: true);
     callMethod('splice', [index, 0, element]);
   }
 
   E removeAt(int index) {
     _checkIndex(index);
     return callMethod('splice', [index, 1])[0];
   }
 
   E removeLast() {
     if (length == 0) throw new RangeError(-1);
@@ skipping 18 matching lines @@
     callMethod('sort', [compare]);
   }
 }
 
 /**
  * Placeholder object for cases where we need to determine exactly how many
  * args were passed to a function.
  */
 const _UNDEFINED = const Object();
 
-// FIXME(jacobr): this method is a hack to work around the lack of proper dart
+// TODO(jacobr): this method is a hack to work around the lack of proper dart
 // support for varargs methods.
 List _stripUndefinedArgs(List args) =>
     args.takeWhile((i) => i != _UNDEFINED).toList();
 
 /**
  * Returns a method that can be called with an arbitrary number (for n less
  * than 11) of arguments without violating Dart type checks.
  */
 Function _wrapAsDebuggerVarArgsFunction(JsFunction jsFunction) =>
-  ([a1=_UNDEFINED, a2=_UNDEFINED, a3=_UNDEFINED, a4=_UNDEFINED,
-    a5=_UNDEFINED, a6=_UNDEFINED, a7=_UNDEFINED, a8=_UNDEFINED,
-    a9=_UNDEFINED, a10=_UNDEFINED]) =>
-    jsFunction._applyDebuggerOnly(_stripUndefinedArgs(
-        [a1,a2,a3,a4,a5,a6,a7,a8,a9,a10]));
+    ([a1 = _UNDEFINED, a2 = _UNDEFINED, a3 = _UNDEFINED, a4 = _UNDEFINED,
+        a5 = _UNDEFINED, a6 = _UNDEFINED, a7 = _UNDEFINED, a8 = _UNDEFINED,
+        a9 = _UNDEFINED, a10 = _UNDEFINED]) => jsFunction._applyDebuggerOnly(
+            _stripUndefinedArgs([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]));