fixes #40, extension methods for primitive types

lib/runtime/dart/collection.js

 var collection = dart.defineLibrary(collection, {});
 var _internal = dart.lazyImport(_internal);
 var core = dart.import(core);
 var _js_helper = dart.lazyImport(_js_helper);
 var math = dart.lazyImport(math);
 (function(exports, _internal, core, _js_helper, math) {
   'use strict';
   let _source = Symbol('_source');
   let UnmodifiableListView$ = dart.generic(function(E) {
     class UnmodifiableListView extends _internal.UnmodifiableListBase$(E) {
       UnmodifiableListView(source) {
         this[_source] = source;
       }
-      get [core.$length]() {
-        return this[_source][core.$length];
+      get length() {
+        return this[_source].length;
       }
-      [core.$get](index) {
-        return this[_source][core.$elementAt](index);
+      get(index) {
+        return this[_source][dartx.elementAt](index);
       }
     }
     dart.setSignature(UnmodifiableListView, {
       constructors: () => ({UnmodifiableListView: [exports.UnmodifiableListView$(E), [core.Iterable$(E)]]}),
-      methods: () => ({[core.$get]: [E, [core.int]]})
+      methods: () => ({get: [E, [core.int]]})
     });
     return UnmodifiableListView;
   });
   dart.defineLazyClassGeneric(exports, 'UnmodifiableListView', {get: UnmodifiableListView$});
   function _defaultEquals(a, b) {
     return dart.equals(a, b);
   }
   dart.fn(_defaultEquals, core.bool, [core.Object, core.Object]);
   function _defaultHashCode(a) {
     return dart.hashCode(a);
@@ skipping 71 matching lines @@
         fromIterable: [HashMap$(K, V), [core.Iterable], {key: dart.functionType(K, [dart.bottom]), value: dart.functionType(V, [dart.bottom])}],
         fromIterables: [HashMap$(K, V), [core.Iterable$(K), core.Iterable$(V)]]
       })
     });
     return HashMap;
   });
   let HashMap = HashMap$();
   let SetMixin$ = dart.generic(function(E) {
     class SetMixin extends core.Object {
       [Symbol.iterator]() {
-        return new dart.JsIterator(this[core.$iterator]);
+        return new dart.JsIterator(this.iterator);
       }
-      get [core.$isEmpty]() {
-        return this[core.$length] == 0;
+      get isEmpty() {
+        return this.length == 0;
       }
-      get [core.$isNotEmpty]() {
-        return this[core.$length] != 0;
+      get isNotEmpty() {
+        return this.length != 0;
       }
       clear() {
-        this.removeAll(this[core.$toList]());
+        this.removeAll(this.toList());
       }
       addAll(elements) {
         dart.as(elements, core.Iterable$(E));
         for (let element of elements)
           this.add(element);
       }
       removeAll(elements) {
         for (let element of elements)
           this.remove(element);
       }
       retainAll(elements) {
-        let toRemove = this[core.$toSet]();
+        let toRemove = this.toSet();
         for (let o of elements) {
           toRemove.remove(o);
         }
         this.removeAll(toRemove);
       }
       removeWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let toRemove = [];
         for (let element of this) {
           if (test(element))
-            toRemove[core.$add](element);
+            toRemove[dartx.add](element);
         }
         this.removeAll(toRemove);
       }
       retainWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let toRemove = [];
         for (let element of this) {
           if (!dart.notNull(test(element)))
-            toRemove[core.$add](element);
+            toRemove[dartx.add](element);
         }
         this.removeAll(toRemove);
       }
       containsAll(other) {
         for (let o of other) {
-          if (!dart.notNull(this[core.$contains](o)))
+          if (!dart.notNull(this.contains(o)))
             return false;
         }
         return true;
       }
       union(other) {
         dart.as(other, core.Set$(E));
-        let _ = this[core.$toSet]();
+        let _ = this.toSet();
         _.addAll(other);
         return _;
       }
       intersection(other) {
-        let result = this[core.$toSet]();
+        let result = this.toSet();
         for (let element of this) {
-          if (!dart.notNull(other[core.$contains](element)))
+          if (!dart.notNull(other.contains(element)))
             result.remove(element);
         }
         return result;
       }
       difference(other) {
-        let result = this[core.$toSet]();
+        let result = this.toSet();
         for (let element of this) {
-          if (other[core.$contains](element))
+          if (other.contains(element))
             result.remove(element);
         }
         return result;
       }
-      [core.$toList](opts) {
+      toList(opts) {
         let growable = opts && 'growable' in opts ? opts.growable : true;
         let result = growable ? (() => {
           let _ = core.List$(E).new();
-          _[core.$length] = this[core.$length];
+          _.length = this.length;
           return _;
-        }).bind(this)() : core.List$(E).new(this[core.$length]);
+        }).bind(this)() : core.List$(E).new(this.length);
         let i = 0;
         for (let element of this)
-          result[core.$set]((() => {
+          result[dartx.set]((() => {
             let x = i;
             i = dart.notNull(x) + 1;
             return x;
           })(), element);
         return result;
       }
-      [core.$map](f) {
+      map(f) {
         dart.as(f, dart.functionType(core.Object, [E]));
         return new (_internal.EfficientLengthMappedIterable$(E, core.Object))(this, f);
       }
-      get [core.$single]() {
-        if (dart.notNull(this[core.$length]) > 1)
+      get single() {
+        if (dart.notNull(this.length) > 1)
           throw _internal.IterableElementError.tooMany();
-        let it = this[core.$iterator];
+        let it = this.iterator;
         if (!dart.notNull(it.moveNext()))
           throw _internal.IterableElementError.noElement();
         let result = it.current;
         return result;
       }
       toString() {
         return IterableBase.iterableToFullString(this, '{', '}');
       }
-      [core.$where](f) {
+      where(f) {
         dart.as(f, dart.functionType(core.bool, [E]));
         return new (_internal.WhereIterable$(E))(this, f);
       }
-      [core.$expand](f) {
+      expand(f) {
         dart.as(f, dart.functionType(core.Iterable, [E]));
         return new (_internal.ExpandIterable$(E, core.Object))(this, f);
       }
-      [core.$forEach](f) {
+      forEach(f) {
         dart.as(f, dart.functionType(dart.void, [E]));
         for (let element of this)
           f(element);
       }
-      [core.$reduce](combine) {
+      reduce(combine) {
         dart.as(combine, dart.functionType(E, [E, E]));
-        let iterator = this[core.$iterator];
+        let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         let value = iterator.current;
         while (iterator.moveNext()) {
           value = combine(value, iterator.current);
         }
         return value;
       }
-      [core.$fold](initialValue, combine) {
+      fold(initialValue, combine) {
         dart.as(combine, dart.functionType(core.Object, [dart.bottom, E]));
         let value = initialValue;
         for (let element of this)
           value = dart.dcall(combine, value, element);
         return value;
       }
-      [core.$every](f) {
+      every(f) {
         dart.as(f, dart.functionType(core.bool, [E]));
         for (let element of this) {
           if (!dart.notNull(f(element)))
             return false;
         }
         return true;
       }
-      [core.$join](separator) {
+      join(separator) {
         if (separator === void 0)
           separator = "";
-        let iterator = this[core.$iterator];
+        let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext()))
           return "";
         let buffer = new core.StringBuffer();
         if (separator == null || separator == "") {
           do {
             buffer.write(`${iterator.current}`);
           } while (iterator.moveNext());
         } else {
           buffer.write(`${iterator.current}`);
           while (iterator.moveNext()) {
             buffer.write(separator);
             buffer.write(`${iterator.current}`);
           }
         }
         return dart.toString(buffer);
       }
-      [core.$any](test) {
+      any(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         for (let element of this) {
           if (test(element))
             return true;
         }
         return false;
       }
-      [core.$take](n) {
+      take(n) {
         return _internal.TakeIterable$(E).new(this, n);
       }
-      [core.$takeWhile](test) {
+      takeWhile(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.TakeWhileIterable$(E))(this, test);
       }
-      [core.$skip](n) {
+      skip(n) {
         return _internal.SkipIterable$(E).new(this, n);
       }
-      [core.$skipWhile](test) {
+      skipWhile(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.SkipWhileIterable$(E))(this, test);
       }
-      get [core.$first]() {
-        let it = this[core.$iterator];
+      get first() {
+        let it = this.iterator;
         if (!dart.notNull(it.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         return it.current;
       }
-      get [core.$last]() {
-        let it = this[core.$iterator];
+      get last() {
+        let it = this.iterator;
         if (!dart.notNull(it.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         let result = null;
         do {
           result = it.current;
         } while (it.moveNext());
         return result;
       }
-      [core.$firstWhere](test, opts) {
+      firstWhere(test, opts) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         dart.as(orElse, dart.functionType(E, []));
         for (let element of this) {
           if (test(element))
             return element;
         }
         if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
-      [core.$lastWhere](test, opts) {
+      lastWhere(test, opts) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         dart.as(orElse, dart.functionType(E, []));
         let result = null;
         let foundMatching = false;
         for (let element of this) {
           if (test(element)) {
             result = element;
             foundMatching = true;
           }
         }
         if (foundMatching)
           return result;
         if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
-      [core.$singleWhere](test) {
+      singleWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let result = null;
         let foundMatching = false;
         for (let element of this) {
           if (test(element)) {
             if (foundMatching) {
               throw _internal.IterableElementError.tooMany();
             }
             result = element;
             foundMatching = true;
           }
         }
         if (foundMatching)
           return result;
         throw _internal.IterableElementError.noElement();
       }
-      [core.$elementAt](index) {
+      elementAt(index) {
         if (!(typeof index == 'number'))
           throw new core.ArgumentError.notNull("index");
         core.RangeError.checkNotNegative(index, "index");
         let elementIndex = 0;
         for (let element of this) {
           if (index == elementIndex)
             return element;
           elementIndex = dart.notNull(elementIndex) + 1;
         }
         throw core.RangeError.index(index, this, "index", null, elementIndex);
       }
     }
     SetMixin[dart.implements] = () => [core.Set$(E)];
+    dart.implementExtension(SetMixin, () => [core.Iterable]);
     dart.setSignature(SetMixin, {
       methods: () => ({
         clear: [dart.void, []],
         addAll: [dart.void, [core.Iterable$(E)]],
         removeAll: [dart.void, [core.Iterable$(core.Object)]],
         retainAll: [dart.void, [core.Iterable$(core.Object)]],
         removeWhere: [dart.void, [dart.functionType(core.bool, [E])]],
         retainWhere: [dart.void, [dart.functionType(core.bool, [E])]],
         containsAll: [core.bool, [core.Iterable$(core.Object)]],
         union: [core.Set$(E), [core.Set$(E)]],
         intersection: [core.Set$(E), [core.Set$(core.Object)]],
         difference: [core.Set$(E), [core.Set$(core.Object)]],
-        [core.$toList]: [core.List$(E), [], {growable: core.bool}],
-        [core.$map]: [core.Iterable, [dart.functionType(core.Object, [E])]],
-        [core.$where]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$expand]: [core.Iterable, [dart.functionType(core.Iterable, [E])]],
-        [core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]],
-        [core.$reduce]: [E, [dart.functionType(E, [E, E])]],
-        [core.$fold]: [core.Object, [core.Object, dart.functionType(core.Object, [dart.bottom, E])]],
-        [core.$every]: [core.bool, [dart.functionType(core.bool, [E])]],
-        [core.$join]: [core.String, [], [core.String]],
-        [core.$any]: [core.bool, [dart.functionType(core.bool, [E])]],
-        [core.$take]: [core.Iterable$(E), [core.int]],
-        [core.$takeWhile]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$skip]: [core.Iterable$(E), [core.int]],
-        [core.$skipWhile]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$firstWhere]: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
-        [core.$lastWhere]: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
-        [core.$singleWhere]: [E, [dart.functionType(core.bool, [E])]],
-        [core.$elementAt]: [E, [core.int]]
+        toList: [core.List$(E), [], {growable: core.bool}],
+        map: [core.Iterable, [dart.functionType(core.Object, [E])]],
+        where: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        expand: [core.Iterable, [dart.functionType(core.Iterable, [E])]],
+        forEach: [dart.void, [dart.functionType(dart.void, [E])]],
+        reduce: [E, [dart.functionType(E, [E, E])]],
+        fold: [core.Object, [core.Object, dart.functionType(core.Object, [dart.bottom, E])]],
+        every: [core.bool, [dart.functionType(core.bool, [E])]],
+        join: [core.String, [], [core.String]],
+        any: [core.bool, [dart.functionType(core.bool, [E])]],
+        take: [core.Iterable$(E), [core.int]],
+        takeWhile: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        skip: [core.Iterable$(E), [core.int]],
+        skipWhile: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        firstWhere: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
+        lastWhere: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
+        singleWhere: [E, [dart.functionType(core.bool, [E])]],
+        elementAt: [E, [core.int]]
       })
     });
     return SetMixin;
   });
   let SetMixin = SetMixin$();
   let SetBase$ = dart.generic(function(E) {
     class SetBase extends SetMixin$(E) {
       static setToString(set) {
         return IterableBase.iterableToFullString(set, '{', '}');
       }
     }
     dart.setSignature(SetBase, {
       statics: () => ({setToString: [core.String, [core.Set]]}),
       names: ['setToString']
     });
     return SetBase;
   });
   let SetBase = SetBase$();
   let _newSet = Symbol('_newSet');
   let _HashSetBase$ = dart.generic(function(E) {
     class _HashSetBase extends SetBase$(E) {
       difference(other) {
         let result = this[_newSet]();
         for (let element of this) {
-          if (!dart.notNull(other[core.$contains](element)))
+          if (!dart.notNull(other.contains(element)))
             result.add(element);
         }
         return result;
       }
       intersection(other) {
         let result = this[_newSet]();
         for (let element of this) {
-          if (other[core.$contains](element))
+          if (other.contains(element))
             result.add(element);
         }
         return result;
       }
-      [core.$toSet]() {
+      toSet() {
         return (() => {
           let _ = this[_newSet]();
           _.addAll(this);
           return _;
         }).bind(this)();
       }
     }
     dart.setSignature(_HashSetBase, {
       methods: () => ({
         difference: [core.Set$(E), [core.Set$(core.Object)]],
         intersection: [core.Set$(E), [core.Set$(core.Object)]],
-        [core.$toSet]: [core.Set$(E), []]
+        toSet: [core.Set$(E), []]
       })
     });
     return _HashSetBase;
   });
   let _HashSetBase = _HashSetBase$();
   let HashSet$ = dart.generic(function(E) {
     class HashSet extends core.Object {
       static new(opts) {
         let equals = opts && 'equals' in opts ? opts.equals : null;
         let hashCode = opts && 'hashCode' in opts ? opts.hashCode : null;
@@ skipping 25 matching lines @@
       static identity() {
         return new (_IdentityHashSet$(E))();
       }
       static from(elements) {
         let result = HashSet$(E).new();
         for (let e of dart.as(elements, core.Iterable$(E)))
           result.add(e);
         return result;
       }
       [Symbol.iterator]() {
-        return new dart.JsIterator(this[core.$iterator]);
+        return new dart.JsIterator(this.iterator);
       }
     }
     HashSet[dart.implements] = () => [core.Set$(E)];
+    dart.implementExtension(HashSet, () => [core.Iterable]);
     dart.setSignature(HashSet, {
       constructors: () => ({
         new: [HashSet$(E), [], {equals: dart.functionType(core.bool, [E, E]), hashCode: dart.functionType(core.int, [E]), isValidKey: dart.functionType(core.bool, [core.Object])}],
         identity: [HashSet$(E), []],
         from: [HashSet$(E), [core.Iterable]]
       })
     });
     return HashSet;
   });
   let HashSet = HashSet$();
   let IterableMixin$ = dart.generic(function(E) {
     class IterableMixin extends core.Object {
-      [core.$map](f) {
+      map(f) {
         dart.as(f, dart.functionType(core.Object, [E]));
         return _internal.MappedIterable$(E, core.Object).new(this, f);
       }
-      [core.$where](f) {
+      where(f) {
         dart.as(f, dart.functionType(core.bool, [E]));
         return new (_internal.WhereIterable$(E))(this, f);
       }
-      [core.$expand](f) {
+      expand(f) {
         dart.as(f, dart.functionType(core.Iterable, [E]));
         return new (_internal.ExpandIterable$(E, core.Object))(this, f);
       }
-      [core.$contains](element) {
+      contains(element) {
         for (let e of this) {
           if (dart.equals(e, element))
             return true;
         }
         return false;
       }
-      [core.$forEach](f) {
+      forEach(f) {
         dart.as(f, dart.functionType(dart.void, [E]));
         for (let element of this)
           f(element);
       }
-      [core.$reduce](combine) {
+      reduce(combine) {
         dart.as(combine, dart.functionType(E, [E, E]));
-        let iterator = this[core.$iterator];
+        let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         let value = iterator.current;
         while (iterator.moveNext()) {
           value = combine(value, iterator.current);
         }
         return value;
       }
-      [core.$fold](initialValue, combine) {
+      fold(initialValue, combine) {
         dart.as(combine, dart.functionType(core.Object, [dart.bottom, E]));
         let value = initialValue;
         for (let element of this)
           value = dart.dcall(combine, value, element);
         return value;
       }
-      [core.$every](f) {
+      every(f) {
         dart.as(f, dart.functionType(core.bool, [E]));
         for (let element of this) {
           if (!dart.notNull(f(element)))
             return false;
         }
         return true;
       }
-      [core.$join](separator) {
+      join(separator) {
         if (separator === void 0)
           separator = "";
-        let iterator = this[core.$iterator];
+        let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext()))
           return "";
         let buffer = new core.StringBuffer();
         if (separator == null || separator == "") {
           do {
             buffer.write(`${iterator.current}`);
           } while (iterator.moveNext());
         } else {
           buffer.write(`${iterator.current}`);
           while (iterator.moveNext()) {
             buffer.write(separator);
             buffer.write(`${iterator.current}`);
           }
         }
         return dart.toString(buffer);
       }
-      [core.$any](f) {
+      any(f) {
         dart.as(f, dart.functionType(core.bool, [E]));
         for (let element of this) {
           if (f(element))
             return true;
         }
         return false;
       }
-      [core.$toList](opts) {
+      toList(opts) {
         let growable = opts && 'growable' in opts ? opts.growable : true;
         return core.List$(E).from(this, {growable: growable});
       }
-      [core.$toSet]() {
+      toSet() {
         return core.Set$(E).from(this);
       }
-      get [core.$length]() {
+      get length() {
         dart.assert(!dart.is(this, _internal.EfficientLength));
         let count = 0;
-        let it = this[core.$iterator];
+        let it = this[dartx.iterator];
         while (it.moveNext()) {
           count = dart.notNull(count) + 1;
         }
         return count;
       }
-      get [core.$isEmpty]() {
-        return !dart.notNull(this[core.$iterator].moveNext());
+      get isEmpty() {
+        return !dart.notNull(this[dartx.iterator].moveNext());
       }
-      get [core.$isNotEmpty]() {
-        return !dart.notNull(this[core.$isEmpty]);
+      get isNotEmpty() {
+        return !dart.notNull(this.isEmpty);
       }
-      [core.$take](n) {
+      take(n) {
         return _internal.TakeIterable$(E).new(this, n);
       }
-      [core.$takeWhile](test) {
+      takeWhile(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.TakeWhileIterable$(E))(this, test);
       }
-      [core.$skip](n) {
+      skip(n) {
         return _internal.SkipIterable$(E).new(this, n);
       }
-      [core.$skipWhile](test) {
+      skipWhile(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.SkipWhileIterable$(E))(this, test);
       }
-      get [core.$first]() {
-        let it = this[core.$iterator];
+      get first() {
+        let it = this[dartx.iterator];
         if (!dart.notNull(it.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         return it.current;
       }
-      get [core.$last]() {
-        let it = this[core.$iterator];
+      get last() {
+        let it = this[dartx.iterator];
         if (!dart.notNull(it.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         let result = null;
         do {
           result = it.current;
         } while (it.moveNext());
         return result;
       }
-      get [core.$single]() {
-        let it = this[core.$iterator];
+      get single() {
+        let it = this[dartx.iterator];
         if (!dart.notNull(it.moveNext()))
           throw _internal.IterableElementError.noElement();
         let result = it.current;
         if (it.moveNext())
           throw _internal.IterableElementError.tooMany();
         return result;
       }
-      [core.$firstWhere](test, opts) {
+      firstWhere(test, opts) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         dart.as(orElse, dart.functionType(E, []));
         for (let element of this) {
           if (test(element))
             return element;
         }
         if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
-      [core.$lastWhere](test, opts) {
+      lastWhere(test, opts) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         dart.as(orElse, dart.functionType(E, []));
         let result = null;
         let foundMatching = false;
         for (let element of this) {
           if (test(element)) {
             result = element;
             foundMatching = true;
           }
         }
         if (foundMatching)
           return result;
         if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
-      [core.$singleWhere](test) {
+      singleWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let result = null;
         let foundMatching = false;
         for (let element of this) {
           if (test(element)) {
             if (foundMatching) {
               throw _internal.IterableElementError.tooMany();
             }
             result = element;
             foundMatching = true;
           }
         }
         if (foundMatching)
           return result;
         throw _internal.IterableElementError.noElement();
       }
-      [core.$elementAt](index) {
+      elementAt(index) {
         if (!(typeof index == 'number'))
           throw new core.ArgumentError.notNull("index");
         core.RangeError.checkNotNegative(index, "index");
         let elementIndex = 0;
         for (let element of this) {
           if (index == elementIndex)
             return element;
           elementIndex = dart.notNull(elementIndex) + 1;
         }
         throw core.RangeError.index(index, this, "index", null, elementIndex);
       }
       toString() {
         return IterableBase.iterableToShortString(this, '(', ')');
       }
       [Symbol.iterator]() {
-        return new dart.JsIterator(this[core.$iterator]);
+        return new dart.JsIterator(this.iterator);
       }
     }
     IterableMixin[dart.implements] = () => [core.Iterable$(E)];
+    dart.implementExtension(IterableMixin, () => [core.Iterable]);
     dart.setSignature(IterableMixin, {
       methods: () => ({
-        [core.$map]: [core.Iterable, [dart.functionType(core.Object, [E])]],
-        [core.$where]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$expand]: [core.Iterable, [dart.functionType(core.Iterable, [E])]],
-        [core.$contains]: [core.bool, [core.Object]],
-        [core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]],
-        [core.$reduce]: [E, [dart.functionType(E, [E, E])]],
-        [core.$fold]: [core.Object, [core.Object, dart.functionType(core.Object, [dart.bottom, E])]],
-        [core.$every]: [core.bool, [dart.functionType(core.bool, [E])]],
-        [core.$join]: [core.String, [], [core.String]],
-        [core.$any]: [core.bool, [dart.functionType(core.bool, [E])]],
-        [core.$toList]: [core.List$(E), [], {growable: core.bool}],
-        [core.$toSet]: [core.Set$(E), []],
-        [core.$take]: [core.Iterable$(E), [core.int]],
-        [core.$takeWhile]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$skip]: [core.Iterable$(E), [core.int]],
-        [core.$skipWhile]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$firstWhere]: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
-        [core.$lastWhere]: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
-        [core.$singleWhere]: [E, [dart.functionType(core.bool, [E])]],
-        [core.$elementAt]: [E, [core.int]]
+        map: [core.Iterable, [dart.functionType(core.Object, [E])]],
+        where: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        expand: [core.Iterable, [dart.functionType(core.Iterable, [E])]],
+        contains: [core.bool, [core.Object]],
+        forEach: [dart.void, [dart.functionType(dart.void, [E])]],
+        reduce: [E, [dart.functionType(E, [E, E])]],
+        fold: [core.Object, [core.Object, dart.functionType(core.Object, [dart.bottom, E])]],
+        every: [core.bool, [dart.functionType(core.bool, [E])]],
+        join: [core.String, [], [core.String]],
+        any: [core.bool, [dart.functionType(core.bool, [E])]],
+        toList: [core.List$(E), [], {growable: core.bool}],
+        toSet: [core.Set$(E), []],
+        take: [core.Iterable$(E), [core.int]],
+        takeWhile: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        skip: [core.Iterable$(E), [core.int]],
+        skipWhile: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        firstWhere: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
+        lastWhere: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
+        singleWhere: [E, [dart.functionType(core.bool, [E])]],
+        elementAt: [E, [core.int]]
       })
     });
     return IterableMixin;
   });
   let IterableMixin = IterableMixin$();
   let IterableBase$ = dart.generic(function(E) {
     class IterableBase extends core.Object {
       IterableBase() {
       }
-      [core.$map](f) {
+      map(f) {
         dart.as(f, dart.functionType(core.Object, [E]));
         return _internal.MappedIterable$(E, core.Object).new(this, f);
       }
-      [core.$where](f) {
+      where(f) {
         dart.as(f, dart.functionType(core.bool, [E]));
         return new (_internal.WhereIterable$(E))(this, f);
       }
-      [core.$expand](f) {
+      expand(f) {
         dart.as(f, dart.functionType(core.Iterable, [E]));
         return new (_internal.ExpandIterable$(E, core.Object))(this, f);
       }
-      [core.$contains](element) {
+      contains(element) {
         for (let e of this) {
           if (dart.equals(e, element))
             return true;
         }
         return false;
       }
-      [core.$forEach](f) {
+      forEach(f) {
         dart.as(f, dart.functionType(dart.void, [E]));
         for (let element of this)
           f(element);
       }
-      [core.$reduce](combine) {
+      reduce(combine) {
         dart.as(combine, dart.functionType(E, [E, E]));
-        let iterator = this[core.$iterator];
+        let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         let value = iterator.current;
         while (iterator.moveNext()) {
           value = combine(value, iterator.current);
         }
         return value;
       }
-      [core.$fold](initialValue, combine) {
+      fold(initialValue, combine) {
         dart.as(combine, dart.functionType(core.Object, [dart.bottom, E]));
         let value = initialValue;
         for (let element of this)
           value = dart.dcall(combine, value, element);
         return value;
       }
-      [core.$every](f) {
+      every(f) {
         dart.as(f, dart.functionType(core.bool, [E]));
         for (let element of this) {
           if (!dart.notNull(f(element)))
             return false;
         }
         return true;
       }
-      [core.$join](separator) {
+      join(separator) {
         if (separator === void 0)
           separator = "";
-        let iterator = this[core.$iterator];
+        let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext()))
           return "";
         let buffer = new core.StringBuffer();
         if (separator == null || separator == "") {
           do {
             buffer.write(`${iterator.current}`);
           } while (iterator.moveNext());
         } else {
           buffer.write(`${iterator.current}`);
           while (iterator.moveNext()) {
             buffer.write(separator);
             buffer.write(`${iterator.current}`);
           }
         }
         return dart.toString(buffer);
       }
-      [core.$any](f) {
+      any(f) {
         dart.as(f, dart.functionType(core.bool, [E]));
         for (let element of this) {
           if (f(element))
             return true;
         }
         return false;
       }
-      [core.$toList](opts) {
+      toList(opts) {
         let growable = opts && 'growable' in opts ? opts.growable : true;
         return core.List$(E).from(this, {growable: growable});
       }
-      [core.$toSet]() {
+      toSet() {
         return core.Set$(E).from(this);
       }
-      get [core.$length]() {
+      get length() {
         dart.assert(!dart.is(this, _internal.EfficientLength));
         let count = 0;
-        let it = this[core.$iterator];
+        let it = this[dartx.iterator];
         while (it.moveNext()) {
           count = dart.notNull(count) + 1;
         }
         return count;
       }
-      get [core.$isEmpty]() {
-        return !dart.notNull(this[core.$iterator].moveNext());
+      get isEmpty() {
+        return !dart.notNull(this[dartx.iterator].moveNext());
       }
-      get [core.$isNotEmpty]() {
-        return !dart.notNull(this[core.$isEmpty]);
+      get isNotEmpty() {
+        return !dart.notNull(this.isEmpty);
       }
-      [core.$take](n) {
+      take(n) {
         return _internal.TakeIterable$(E).new(this, n);
       }
-      [core.$takeWhile](test) {
+      takeWhile(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.TakeWhileIterable$(E))(this, test);
       }
-      [core.$skip](n) {
+      skip(n) {
         return _internal.SkipIterable$(E).new(this, n);
       }
-      [core.$skipWhile](test) {
+      skipWhile(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.SkipWhileIterable$(E))(this, test);
       }
-      get [core.$first]() {
-        let it = this[core.$iterator];
+      get first() {
+        let it = this[dartx.iterator];
         if (!dart.notNull(it.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         return it.current;
       }
-      get [core.$last]() {
-        let it = this[core.$iterator];
+      get last() {
+        let it = this[dartx.iterator];
         if (!dart.notNull(it.moveNext())) {
           throw _internal.IterableElementError.noElement();
         }
         let result = null;
         do {
           result = it.current;
         } while (it.moveNext());
         return result;
       }
-      get [core.$single]() {
-        let it = this[core.$iterator];
+      get single() {
+        let it = this[dartx.iterator];
         if (!dart.notNull(it.moveNext()))
           throw _internal.IterableElementError.noElement();
         let result = it.current;
         if (it.moveNext())
           throw _internal.IterableElementError.tooMany();
         return result;
       }
-      [core.$firstWhere](test, opts) {
+      firstWhere(test, opts) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         dart.as(orElse, dart.functionType(E, []));
         for (let element of this) {
           if (test(element))
             return element;
         }
         if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
-      [core.$lastWhere](test, opts) {
+      lastWhere(test, opts) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         dart.as(orElse, dart.functionType(E, []));
         let result = null;
         let foundMatching = false;
         for (let element of this) {
           if (test(element)) {
             result = element;
             foundMatching = true;
           }
         }
         if (foundMatching)
           return result;
         if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
-      [core.$singleWhere](test) {
+      singleWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let result = null;
         let foundMatching = false;
         for (let element of this) {
           if (test(element)) {
             if (foundMatching) {
               throw _internal.IterableElementError.tooMany();
             }
             result = element;
             foundMatching = true;
           }
         }
         if (foundMatching)
           return result;
         throw _internal.IterableElementError.noElement();
       }
-      [core.$elementAt](index) {
+      elementAt(index) {
         if (!(typeof index == 'number'))
           throw new core.ArgumentError.notNull("index");
         core.RangeError.checkNotNegative(index, "index");
         let elementIndex = 0;
         for (let element of this) {
           if (index == elementIndex)
             return element;
           elementIndex = dart.notNull(elementIndex) + 1;
         }
         throw core.RangeError.index(index, this, "index", null, elementIndex);
       }
       toString() {
         return IterableBase$().iterableToShortString(this, '(', ')');
       }
       static iterableToShortString(iterable, leftDelimiter, rightDelimiter) {
         if (leftDelimiter === void 0)
           leftDelimiter = '(';
         if (rightDelimiter === void 0)
           rightDelimiter = ')';
         if (IterableBase$()._isToStringVisiting(iterable)) {
           if (leftDelimiter == "(" && rightDelimiter == ")") {
             return "(...)";
           }
           return `${leftDelimiter}...${rightDelimiter}`;
         }
         let parts = [];
-        IterableBase$()._toStringVisiting[core.$add](iterable);
+        IterableBase$()._toStringVisiting[dartx.add](iterable);
         try {
           IterableBase$()._iterablePartsToStrings(iterable, parts);
         } finally {
-          dart.assert(core.identical(IterableBase$()._toStringVisiting[core.$last], iterable));
-          IterableBase$()._toStringVisiting[core.$removeLast]();
+          dart.assert(core.identical(IterableBase$()._toStringVisiting[dartx.last], iterable));
+          IterableBase$()._toStringVisiting[dartx.removeLast]();
         }
         return dart.toString((() => {
           let _ = new core.StringBuffer(leftDelimiter);
           _.writeAll(parts, ", ");
           _.write(rightDelimiter);
           return _;
         })());
       }
       static iterableToFullString(iterable, leftDelimiter, rightDelimiter) {
         if (leftDelimiter === void 0)
           leftDelimiter = '(';
         if (rightDelimiter === void 0)
           rightDelimiter = ')';
         if (IterableBase$()._isToStringVisiting(iterable)) {
           return `${leftDelimiter}...${rightDelimiter}`;
         }
         let buffer = new core.StringBuffer(leftDelimiter);
-        IterableBase$()._toStringVisiting[core.$add](iterable);
+        IterableBase$()._toStringVisiting[dartx.add](iterable);
         try {
           buffer.writeAll(iterable, ", ");
         } finally {
-          dart.assert(core.identical(IterableBase$()._toStringVisiting[core.$last], iterable));
-          IterableBase$()._toStringVisiting[core.$removeLast]();
+          dart.assert(core.identical(IterableBase$()._toStringVisiting[dartx.last], iterable));
+          IterableBase$()._toStringVisiting[dartx.removeLast]();
         }
         buffer.write(rightDelimiter);
         return dart.toString(buffer);
       }
       static _isToStringVisiting(o) {
-        for (let i = 0; dart.notNull(i) < dart.notNull(IterableBase$()._toStringVisiting[core.$length]); i = dart.notNull(i) + 1) {
-          if (core.identical(o, IterableBase$()._toStringVisiting[core.$get](i)))
+        for (let i = 0; dart.notNull(i) < dart.notNull(IterableBase$()._toStringVisiting.length); i = dart.notNull(i) + 1) {
+          if (core.identical(o, IterableBase$()._toStringVisiting[dartx.get](i)))
             return true;
         }
         return false;
       }
       static _iterablePartsToStrings(iterable, parts) {
         let LENGTH_LIMIT = 80;
         let HEAD_COUNT = 3;
         let TAIL_COUNT = 2;
         let MAX_COUNT = 100;
         let OVERHEAD = 2;
         let ELLIPSIS_SIZE = 3;
         let length = 0;
         let count = 0;
-        let it = iterable[core.$iterator];
+        let it = iterable[dartx.iterator];
         while (dart.notNull(length) < dart.notNull(LENGTH_LIMIT) || dart.notNull(count) < dart.notNull(HEAD_COUNT)) {
           if (!dart.notNull(it.moveNext()))
             return;
           let next = `${it.current}`;
-          parts[core.$add](next);
+          parts[dartx.add](next);
           length = dart.notNull(length) + (dart.notNull(next.length) + dart.notNull(OVERHEAD));
           count = dart.notNull(count) + 1;
         }
         let penultimateString = null;
         let ultimateString = null;
         let penultimate = null;
         let ultimate = null;
         if (!dart.notNull(it.moveNext())) {
           if (dart.notNull(count) <= dart.notNull(HEAD_COUNT) + dart.notNull(TAIL_COUNT))
             return;
-          ultimateString = dart.as(parts[core.$removeLast](), core.String);
-          penultimateString = dart.as(parts[core.$removeLast](), core.String);
+          ultimateString = dart.as(parts[dartx.removeLast](), core.String);
+          penultimateString = dart.as(parts[dartx.removeLast](), core.String);
         } else {
           penultimate = it.current;
           count = dart.notNull(count) + 1;
           if (!dart.notNull(it.moveNext())) {
             if (dart.notNull(count) <= dart.notNull(HEAD_COUNT) + 1) {
-              parts[core.$add](`${penultimate}`);
+              parts[dartx.add](`${penultimate}`);
               return;
             }
             ultimateString = `${penultimate}`;
-            penultimateString = dart.as(parts[core.$removeLast](), core.String);
+            penultimateString = dart.as(parts[dartx.removeLast](), core.String);
             length = dart.notNull(length) + (dart.notNull(ultimateString.length) + dart.notNull(OVERHEAD));
           } else {
             ultimate = it.current;
             count = dart.notNull(count) + 1;
             dart.assert(dart.notNull(count) < dart.notNull(MAX_COUNT));
             while (it.moveNext()) {
               penultimate = ultimate;
               ultimate = it.current;
               count = dart.notNull(count) + 1;
               if (dart.notNull(count) > dart.notNull(MAX_COUNT)) {
                 while (dart.notNull(length) > dart.notNull(LENGTH_LIMIT) - dart.notNull(ELLIPSIS_SIZE) - dart.notNull(OVERHEAD) && dart.notNull(count) > dart.notNull(HEAD_COUNT)) {
-                  length = dart.notNull(length) - dart.notNull(dart.as(dart.dsend(dart.dload(parts[core.$removeLast](), 'length'), '+', OVERHEAD), core.int));
+                  length = dart.notNull(length) - dart.notNull(dart.as(dart.dsend(dart.dload(parts[dartx.removeLast](), 'length'), '+', OVERHEAD), core.int));
                   count = dart.notNull(count) - 1;
                 }
-                parts[core.$add]("...");
+                parts[dartx.add]("...");
                 return;
               }
             }
             penultimateString = `${penultimate}`;
             ultimateString = `${ultimate}`;
             length = dart.notNull(length) + (dart.notNull(ultimateString.length) + dart.notNull(penultimateString.length) + 2 * dart.notNull(OVERHEAD));
           }
         }
         let elision = null;
-        if (dart.notNull(count) > dart.notNull(parts[core.$length]) + dart.notNull(TAIL_COUNT)) {
+        if (dart.notNull(count) > dart.notNull(parts.length) + dart.notNull(TAIL_COUNT)) {
           elision = "...";
           length = dart.notNull(length) + (dart.notNull(ELLIPSIS_SIZE) + dart.notNull(OVERHEAD));
         }
-        while (dart.notNull(length) > dart.notNull(LENGTH_LIMIT) && dart.notNull(parts[core.$length]) > dart.notNull(HEAD_COUNT)) {
-          length = dart.notNull(length) - dart.notNull(dart.as(dart.dsend(dart.dload(parts[core.$removeLast](), 'length'), '+', OVERHEAD), core.int));
+        while (dart.notNull(length) > dart.notNull(LENGTH_LIMIT) && dart.notNull(parts.length) > dart.notNull(HEAD_COUNT)) {
+          length = dart.notNull(length) - dart.notNull(dart.as(dart.dsend(dart.dload(parts[dartx.removeLast](), 'length'), '+', OVERHEAD), core.int));
           if (elision == null) {
             elision = "...";
             length = dart.notNull(length) + (dart.notNull(ELLIPSIS_SIZE) + dart.notNull(OVERHEAD));
           }
         }
         if (elision != null) {
-          parts[core.$add](elision);
+          parts[dartx.add](elision);
         }
-        parts[core.$add](penultimateString);
-        parts[core.$add](ultimateString);
+        parts[dartx.add](penultimateString);
+        parts[dartx.add](ultimateString);
       }
       [Symbol.iterator]() {
-        return new dart.JsIterator(this[core.$iterator]);
+        return new dart.JsIterator(this.iterator);
       }
     }
     IterableBase[dart.implements] = () => [core.Iterable$(E)];
+    dart.implementExtension(IterableBase, () => [core.Iterable]);
     dart.setSignature(IterableBase, {
       constructors: () => ({IterableBase: [IterableBase$(E), []]}),
       methods: () => ({
-        [core.$map]: [core.Iterable, [dart.functionType(core.Object, [E])]],
-        [core.$where]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$expand]: [core.Iterable, [dart.functionType(core.Iterable, [E])]],
-        [core.$contains]: [core.bool, [core.Object]],
-        [core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]],
-        [core.$reduce]: [E, [dart.functionType(E, [E, E])]],
-        [core.$fold]: [core.Object, [core.Object, dart.functionType(core.Object, [dart.bottom, E])]],
-        [core.$every]: [core.bool, [dart.functionType(core.bool, [E])]],
-        [core.$join]: [core.String, [], [core.String]],
-        [core.$any]: [core.bool, [dart.functionType(core.bool, [E])]],
-        [core.$toList]: [core.List$(E), [], {growable: core.bool}],
-        [core.$toSet]: [core.Set$(E), []],
-        [core.$take]: [core.Iterable$(E), [core.int]],
-        [core.$takeWhile]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$skip]: [core.Iterable$(E), [core.int]],
-        [core.$skipWhile]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$firstWhere]: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
-        [core.$lastWhere]: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
-        [core.$singleWhere]: [E, [dart.functionType(core.bool, [E])]],
-        [core.$elementAt]: [E, [core.int]]
+        map: [core.Iterable, [dart.functionType(core.Object, [E])]],
+        where: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        expand: [core.Iterable, [dart.functionType(core.Iterable, [E])]],
+        contains: [core.bool, [core.Object]],
+        forEach: [dart.void, [dart.functionType(dart.void, [E])]],
+        reduce: [E, [dart.functionType(E, [E, E])]],
+        fold: [core.Object, [core.Object, dart.functionType(core.Object, [dart.bottom, E])]],
+        every: [core.bool, [dart.functionType(core.bool, [E])]],
+        join: [core.String, [], [core.String]],
+        any: [core.bool, [dart.functionType(core.bool, [E])]],
+        toList: [core.List$(E), [], {growable: core.bool}],
+        toSet: [core.Set$(E), []],
+        take: [core.Iterable$(E), [core.int]],
+        takeWhile: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        skip: [core.Iterable$(E), [core.int]],
+        skipWhile: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        firstWhere: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
+        lastWhere: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
+        singleWhere: [E, [dart.functionType(core.bool, [E])]],
+        elementAt: [E, [core.int]]
       }),
       statics: () => ({
         iterableToShortString: [core.String, [core.Iterable], [core.String, core.String]],
         iterableToFullString: [core.String, [core.Iterable], [core.String, core.String]],
         _isToStringVisiting: [core.bool, [core.Object]],
         _iterablePartsToStrings: [dart.void, [core.Iterable, core.List]]
       }),
       names: ['iterableToShortString', 'iterableToFullString', '_isToStringVisiting', '_iterablePartsToStrings']
     });
     return IterableBase;
@@ skipping 155 matching lines @@
         return new (_LinkedIdentityHashSet$(E))();
       }
       static from(elements) {
         let result = LinkedHashSet$(E).new();
         for (let element of elements) {
           result.add(element);
         }
         return result;
       }
       [Symbol.iterator]() {
-        return new dart.JsIterator(this[core.$iterator]);
+        return new dart.JsIterator(this.iterator);
       }
     }
     LinkedHashSet[dart.implements] = () => [HashSet$(E)];
+    dart.implementExtension(LinkedHashSet, () => [core.Iterable]);
     dart.setSignature(LinkedHashSet, {
       constructors: () => ({
         new: [LinkedHashSet$(E), [], {equals: dart.functionType(core.bool, [E, E]), hashCode: dart.functionType(core.int, [E]), isValidKey: dart.functionType(core.bool, [core.Object])}],
         identity: [LinkedHashSet$(E), []],
         from: [LinkedHashSet$(E), [core.Iterable$(E)]]
       })
     });
     return LinkedHashSet;
   });
   let LinkedHashSet = LinkedHashSet$();
@@ skipping 17 matching lines @@
       addFirst(entry) {
         dart.as(entry, E);
         this[_insertAfter](this, entry);
       }
       add(entry) {
         dart.as(entry, E);
         this[_insertAfter](this[_previous], entry);
       }
       addAll(entries) {
         dart.as(entries, core.Iterable$(E));
-        entries[core.$forEach](dart.fn((entry => this[_insertAfter](this[_previous], dart.as(entry, E))).bind(this), dart.void, [core.Object]));
+        entries[dartx.forEach](dart.fn((entry => this[_insertAfter](this[_previous], dart.as(entry, E))).bind(this), dart.void, [core.Object]));
       }
       remove(entry) {
         dart.as(entry, E);
         if (!dart.equals(entry[_list], this))
           return false;
         this[_unlink](entry);
         return true;
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (_LinkedListIterator$(E))(this);
       }
-      get [core.$length]() {
+      get length() {
         return this[_length];
       }
       clear() {
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         let next = this[_next];
         while (!dart.notNull(core.identical(next, this))) {
           let entry = dart.as(next, E);
           next = entry[_next];
           entry[_next] = entry[_previous] = entry[_list] = null;
         }
         this[_next] = this[_previous] = this;
         this[_length] = 0;
       }
-      get [core.$first]() {
+      get first() {
         if (core.identical(this[_next], this)) {
           throw new core.StateError('No such element');
         }
         return dart.as(this[_next], E);
       }
-      get [core.$last]() {
+      get last() {
         if (core.identical(this[_previous], this)) {
           throw new core.StateError('No such element');
         }
         return dart.as(this[_previous], E);
       }
-      get [core.$single]() {
+      get single() {
         if (core.identical(this[_previous], this)) {
           throw new core.StateError('No such element');
         }
         if (!dart.notNull(core.identical(this[_previous], this[_next]))) {
           throw new core.StateError('Too many elements');
         }
         return dart.as(this[_next], E);
       }
-      [core.$forEach](action) {
+      forEach(action) {
         dart.as(action, dart.functionType(dart.void, [E]));
         let modificationCount = this[_modificationCount];
         let current = this[_next];
         while (!dart.notNull(core.identical(current, this))) {
           action(dart.as(current, E));
           if (modificationCount != this[_modificationCount]) {
             throw new core.ConcurrentModificationError(this);
           }
           current = current[_next];
         }
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return this[_length] == 0;
       }
       [_insertAfter](entry, newEntry) {
         dart.as(newEntry, E);
         if (newEntry.list != null) {
           throw new core.StateError('LinkedListEntry is already in a LinkedList');
         }
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         newEntry[_list] = this;
         let predecessor = entry;
         let successor = entry[_next];
         successor[_previous] = newEntry;
         newEntry[_previous] = predecessor;
         newEntry[_next] = successor;
         predecessor[_next] = newEntry;
         this[_length] = dart.notNull(this[_length]) + 1;
       }
       [_unlink](entry) {
         dart.as(entry, LinkedListEntry$(E));
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         entry[_next][_previous] = entry[_previous];
         entry[_previous][_next] = entry[_next];
         this[_length] = dart.notNull(this[_length]) - 1;
         entry[_list] = entry[_next] = entry[_previous] = null;
       }
     }
     LinkedList[dart.implements] = () => [_LinkedListLink];
+    dart.implementExtension(LinkedList, () => [core.Iterable]);
     dart.setSignature(LinkedList, {
       constructors: () => ({LinkedList: [LinkedList$(E), []]}),
       methods: () => ({
         addFirst: [dart.void, [E]],
         add: [dart.void, [E]],
         addAll: [dart.void, [core.Iterable$(E)]],
         remove: [core.bool, [E]],
         clear: [dart.void, []],
-        [core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]],
+        forEach: [dart.void, [dart.functionType(dart.void, [E])]],
         [_insertAfter]: [dart.void, [_LinkedListLink, E]],
         [_unlink]: [dart.void, [LinkedListEntry$(E)]]
       })
     });
     return LinkedList;
   });
   let LinkedList = LinkedList$();
   let _current = Symbol('_current');
   let _LinkedListIterator$ = dart.generic(function(E) {
     class _LinkedListIterator extends core.Object {
@@ skipping 72 matching lines @@
         unlink: [dart.void, []],
         insertAfter: [dart.void, [E]],
         insertBefore: [dart.void, [E]]
       })
     });
     return LinkedListEntry;
   });
   let LinkedListEntry = LinkedListEntry$();
   let ListMixin$ = dart.generic(function(E) {
     class ListMixin extends core.Object {
-      get [core.$iterator]() {
+      get iterator() {
         return new (_internal.ListIterator$(E))(this);
       }
       [Symbol.iterator]() {
-        return new dart.JsIterator(this[core.$iterator]);
+        return new dart.JsIterator(this.iterator);
       }
-      [core.$elementAt](index) {
-        return this[core.$get](index);
+      elementAt(index) {
+        return this.get(index);
       }
-      [core.$forEach](action) {
+      forEach(action) {
         dart.as(action, dart.functionType(dart.void, [E]));
-        let length = this[core.$length];
+        let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          action(this[core.$get](i));
-          if (length != this[core.$length]) {
+          action(this.get(i));
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
       }
-      get [core.$isEmpty]() {
-        return this[core.$length] == 0;
+      get isEmpty() {
+        return this.length == 0;
       }
-      get [core.$isNotEmpty]() {
-        return !dart.notNull(this[core.$isEmpty]);
+      get isNotEmpty() {
+        return !dart.notNull(this.isEmpty);
       }
-      get [core.$first]() {
-        if (this[core.$length] == 0)
+      get first() {
+        if (this.length == 0)
           throw _internal.IterableElementError.noElement();
-        return this[core.$get](0);
+        return this.get(0);
       }
-      get [core.$last]() {
-        if (this[core.$length] == 0)
+      get last() {
+        if (this.length == 0)
           throw _internal.IterableElementError.noElement();
-        return this[core.$get](dart.notNull(this[core.$length]) - 1);
+        return this.get(dart.notNull(this.length) - 1);
       }
-      get [core.$single]() {
-        if (this[core.$length] == 0)
+      get single() {
+        if (this.length == 0)
           throw _internal.IterableElementError.noElement();
-        if (dart.notNull(this[core.$length]) > 1)
+        if (dart.notNull(this.length) > 1)
           throw _internal.IterableElementError.tooMany();
-        return this[core.$get](0);
+        return this.get(0);
       }
-      [core.$contains](element) {
-        let length = this[core.$length];
-        for (let i = 0; dart.notNull(i) < dart.notNull(this[core.$length]); i = dart.notNull(i) + 1) {
-          if (dart.equals(this[core.$get](i), element))
+      contains(element) {
+        let length = this.length;
+        for (let i = 0; dart.notNull(i) < dart.notNull(this.length); i = dart.notNull(i) + 1) {
+          if (dart.equals(this.get(i), element))
             return true;
-          if (length != this[core.$length]) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return false;
       }
-      [core.$every](test) {
+      every(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
-        let length = this[core.$length];
+        let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          if (!dart.notNull(test(this[core.$get](i))))
+          if (!dart.notNull(test(this.get(i))))
             return false;
-          if (length != this[core.$length]) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return true;
       }
-      [core.$any](test) {
+      any(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
-        let length = this[core.$length];
+        let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          if (test(this[core.$get](i)))
+          if (test(this.get(i)))
             return true;
-          if (length != this[core.$length]) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return false;
       }
-      [core.$firstWhere](test, opts) {
+      firstWhere(test, opts) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         dart.as(orElse, dart.functionType(E, []));
-        let length = this[core.$length];
+        let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          let element = this[core.$get](i);
+          let element = this.get(i);
           if (test(element))
             return element;
-          if (length != this[core.$length]) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
-      [core.$lastWhere](test, opts) {
+      lastWhere(test, opts) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         dart.as(orElse, dart.functionType(E, []));
-        let length = this[core.$length];
+        let length = this.length;
         for (let i = dart.notNull(length) - 1; dart.notNull(i) >= 0; i = dart.notNull(i) - 1) {
-          let element = this[core.$get](i);
+          let element = this.get(i);
           if (test(element))
             return element;
-          if (length != this[core.$length]) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
-      [core.$singleWhere](test) {
+      singleWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
-        let length = this[core.$length];
+        let length = this.length;
         let match = null;
         let matchFound = false;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          let element = this[core.$get](i);
+          let element = this.get(i);
           if (test(element)) {
             if (matchFound) {
               throw _internal.IterableElementError.tooMany();
             }
             matchFound = true;
             match = element;
           }
-          if (length != this[core.$length]) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         if (matchFound)
           return match;
         throw _internal.IterableElementError.noElement();
       }
-      [core.$join](separator) {
+      join(separator) {
         if (separator === void 0)
           separator = "";
-        if (this[core.$length] == 0)
+        if (this.length == 0)
           return "";
         let buffer = new core.StringBuffer();
         buffer.writeAll(this, separator);
         return dart.toString(buffer);
       }
-      [core.$where](test) {
+      where(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.WhereIterable$(E))(this, test);
       }
-      [core.$map](f) {
+      map(f) {
         dart.as(f, dart.functionType(core.Object, [E]));
         return new _internal.MappedListIterable(this, f);
       }
-      [core.$expand](f) {
+      expand(f) {
         dart.as(f, dart.functionType(core.Iterable, [E]));
         return new (_internal.ExpandIterable$(E, core.Object))(this, f);
       }
-      [core.$reduce](combine) {
+      reduce(combine) {
         dart.as(combine, dart.functionType(E, [E, E]));
-        let length = this[core.$length];
+        let length = this.length;
         if (length == 0)
           throw _internal.IterableElementError.noElement();
-        let value = this[core.$get](0);
+        let value = this.get(0);
         for (let i = 1; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          value = combine(value, this[core.$get](i));
-          if (length != this[core.$length]) {
+          value = combine(value, this.get(i));
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return value;
       }
-      [core.$fold](initialValue, combine) {
+      fold(initialValue, combine) {
         dart.as(combine, dart.functionType(core.Object, [dart.bottom, E]));
         let value = initialValue;
-        let length = this[core.$length];
+        let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          value = dart.dcall(combine, value, this[core.$get](i));
-          if (length != this[core.$length]) {
+          value = dart.dcall(combine, value, this.get(i));
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return value;
       }
-      [core.$skip](count) {
+      skip(count) {
         return new (_internal.SubListIterable$(E))(this, count, null);
       }
-      [core.$skipWhile](test) {
+      skipWhile(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.SkipWhileIterable$(E))(this, test);
       }
-      [core.$take](count) {
+      take(count) {
         return new (_internal.SubListIterable$(E))(this, 0, count);
       }
-      [core.$takeWhile](test) {
+      takeWhile(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         return new (_internal.TakeWhileIterable$(E))(this, test);
       }
-      [core.$toList](opts) {
+      toList(opts) {
         let growable = opts && 'growable' in opts ? opts.growable : true;
         let result = null;
         if (growable) {
           result = core.List$(E).new();
-          result[core.$length] = this[core.$length];
+          result.length = this.length;
         } else {
-          result = core.List$(E).new(this[core.$length]);
-        }
-        for (let i = 0; dart.notNull(i) < dart.notNull(this[core.$length]); i = dart.notNull(i) + 1) {
-          result[core.$set](i, this[core.$get](i));
-        }
-        return result;
-      }
-      [core.$toSet]() {
+          result = core.List$(E).new(this.length);
+        }
+        for (let i = 0; dart.notNull(i) < dart.notNull(this.length); i = dart.notNull(i) + 1) {
+          result[dartx.set](i, this.get(i));
+        }
+        return result;
+      }
+      toSet() {
         let result = core.Set$(E).new();
-        for (let i = 0; dart.notNull(i) < dart.notNull(this[core.$length]); i = dart.notNull(i) + 1) {
-          result.add(this[core.$get](i));
-        }
-        return result;
-      }
-      [core.$add](element) {
+        for (let i = 0; dart.notNull(i) < dart.notNull(this.length); i = dart.notNull(i) + 1) {
+          result.add(this.get(i));
+        }
+        return result;
+      }
+      add(element) {
         dart.as(element, E);
-        this[core.$set]((() => {
-          let x = this[core.$length];
-          this[core.$length] = dart.notNull(x) + 1;
+        this.set((() => {
+          let x = this.length;
+          this.length = dart.notNull(x) + 1;
           return x;
         }).bind(this)(), element);
       }
-      [core.$addAll](iterable) {
+      addAll(iterable) {
         dart.as(iterable, core.Iterable$(E));
         for (let element of iterable) {
-          this[core.$set]((() => {
-            let x = this[core.$length];
-            this[core.$length] = dart.notNull(x) + 1;
+          this.set((() => {
+            let x = this.length;
+            this.length = dart.notNull(x) + 1;
             return x;
           }).bind(this)(), element);
         }
       }
-      [core.$remove](element) {
-        for (let i = 0; dart.notNull(i) < dart.notNull(this[core.$length]); i = dart.notNull(i) + 1) {
-          if (dart.equals(this[core.$get](i), element)) {
-            this[core.$setRange](i, dart.notNull(this[core.$length]) - 1, this, dart.notNull(i) + 1);
-            this[core.$length] = dart.notNull(this[core.$length]) - 1;
+      remove(element) {
+        for (let i = 0; dart.notNull(i) < dart.notNull(this.length); i = dart.notNull(i) + 1) {
+          if (dart.equals(this.get(i), element)) {
+            this.setRange(i, dart.notNull(this.length) - 1, this, dart.notNull(i) + 1);
+            this.length = dart.notNull(this.length) - 1;
             return true;
           }
         }
         return false;
       }
-      [core.$removeWhere](test) {
+      removeWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         ListMixin$()._filter(this, test, false);
       }
-      [core.$retainWhere](test) {
+      retainWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         ListMixin$()._filter(this, test, true);
       }
       static _filter(source, test, retainMatching) {
         dart.as(test, dart.functionType(core.bool, [dart.bottom]));
         let retained = [];
-        let length = source[core.$length];
+        let length = source.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          let element = source[core.$get](i);
+          let element = source[dartx.get](i);
           if (dart.dcall(test, element) == retainMatching) {
-            retained[core.$add](element);
-          }
-          if (length != source[core.$length]) {
+            retained[dartx.add](element);
+          }
+          if (length != source.length) {
             throw new core.ConcurrentModificationError(source);
           }
         }
-        if (retained[core.$length] != source[core.$length]) {
-          source[core.$setRange](0, retained[core.$length], retained);
-          source[core.$length] = retained[core.$length];
-        }
-      }
-      [core.$clear]() {
-        this[core.$length] = 0;
-      }
-      [core.$removeLast]() {
-        if (this[core.$length] == 0) {
+        if (retained.length != source.length) {
+          source[dartx.setRange](0, retained.length, retained);
+          source.length = retained.length;
+        }
+      }
+      clear() {
+        this.length = 0;
+      }
+      removeLast() {
+        if (this.length == 0) {
           throw _internal.IterableElementError.noElement();
         }
-        let result = this[core.$get](dart.notNull(this[core.$length]) - 1);
-        this[core.$length] = dart.notNull(this[core.$length]) - 1;
-        return result;
-      }
-      [core.$sort](compare) {
+        let result = this.get(dart.notNull(this.length) - 1);
+        this.length = dart.notNull(this.length) - 1;
+        return result;
+      }
+      sort(compare) {
         if (compare === void 0)
           compare = null;
         dart.as(compare, dart.functionType(core.int, [E, E]));
         _internal.Sort.sort(this, compare == null ? core.Comparable.compare : compare);
       }
-      [core.$shuffle](random) {
+      shuffle(random) {
         if (random === void 0)
           random = null;
         if (random == null)
           random = math.Random.new();
-        let length = this[core.$length];
+        let length = this.length;
         while (dart.notNull(length) > 1) {
           let pos = random.nextInt(length);
           length = dart.notNull(length) - 1;
-          let tmp = this[core.$get](length);
-          this[core.$set](length, this[core.$get](pos));
-          this[core.$set](pos, tmp);
-        }
-      }
-      [core.$asMap]() {
+          let tmp = this.get(length);
+          this.set(length, this.get(pos));
+          this.set(pos, tmp);
+        }
+      }
+      asMap() {
         return new (_internal.ListMapView$(E))(this);
       }
-      [core.$sublist](start, end) {
+      sublist(start, end) {
         if (end === void 0)
           end = null;
-        let listLength = this[core.$length];
+        let listLength = this.length;
         if (end == null)
           end = listLength;
         core.RangeError.checkValidRange(start, end, listLength);
         let length = dart.notNull(end) - dart.notNull(start);
         let result = core.List$(E).new();
-        result[core.$length] = length;
+        result.length = length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-          result[core.$set](i, this[core.$get](dart.notNull(start) + dart.notNull(i)));
-        }
-        return result;
-      }
-      [core.$getRange](start, end) {
-        core.RangeError.checkValidRange(start, end, this[core.$length]);
+          result[dartx.set](i, this.get(dart.notNull(start) + dart.notNull(i)));
+        }
+        return result;
+      }
+      getRange(start, end) {
+        core.RangeError.checkValidRange(start, end, this.length);
         return new (_internal.SubListIterable$(E))(this, start, end);
       }
-      [core.$removeRange](start, end) {
-        core.RangeError.checkValidRange(start, end, this[core.$length]);
+      removeRange(start, end) {
+        core.RangeError.checkValidRange(start, end, this.length);
         let length = dart.notNull(end) - dart.notNull(start);
-        this[core.$setRange](start, dart.notNull(this[core.$length]) - dart.notNull(length), this, end);
-        this[core.$length] = dart.notNull(this[core.$length]) - dart.notNull(length);
-      }
-      [core.$fillRange](start, end, fill) {
+        this.setRange(start, dart.notNull(this.length) - dart.notNull(length), this, end);
+        this.length = dart.notNull(this.length) - dart.notNull(length);
+      }
+      fillRange(start, end, fill) {
         if (fill === void 0)
           fill = null;
         dart.as(fill, E);
-        core.RangeError.checkValidRange(start, end, this[core.$length]);
+        core.RangeError.checkValidRange(start, end, this.length);
         for (let i = start; dart.notNull(i) < dart.notNull(end); i = dart.notNull(i) + 1) {
-          this[core.$set](i, fill);
-        }
-      }
-      [core.$setRange](start, end, iterable, skipCount) {
+          this.set(i, fill);
+        }
+      }
+      setRange(start, end, iterable, skipCount) {
         dart.as(iterable, core.Iterable$(E));
         if (skipCount === void 0)
           skipCount = 0;
-        core.RangeError.checkValidRange(start, end, this[core.$length]);
+        core.RangeError.checkValidRange(start, end, this.length);
         let length = dart.notNull(end) - dart.notNull(start);
         if (length == 0)
           return;
         core.RangeError.checkNotNegative(skipCount, "skipCount");
         let otherList = null;
         let otherStart = null;
         if (dart.is(iterable, core.List)) {
           otherList = dart.as(iterable, core.List);
           otherStart = skipCount;
         } else {
-          otherList = iterable[core.$skip](skipCount)[core.$toList]({growable: false});
+          otherList = iterable[dartx.skip](skipCount)[dartx.toList]({growable: false});
           otherStart = 0;
         }
-        if (dart.notNull(otherStart) + dart.notNull(length) > dart.notNull(otherList[core.$length])) {
+        if (dart.notNull(otherStart) + dart.notNull(length) > dart.notNull(otherList.length)) {
           throw _internal.IterableElementError.tooFew();
         }
         if (dart.notNull(otherStart) < dart.notNull(start)) {
           for (let i = dart.notNull(length) - 1; dart.notNull(i) >= 0; i = dart.notNull(i) - 1) {
-            this[core.$set](dart.notNull(start) + dart.notNull(i), dart.as(otherList[core.$get](dart.notNull(otherStart) + dart.notNull(i)), E));
+            this.set(dart.notNull(start) + dart.notNull(i), dart.as(otherList[dartx.get](dart.notNull(otherStart) + dart.notNull(i)), E));
           }
         } else {
           for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
-            this[core.$set](dart.notNull(start) + dart.notNull(i), dart.as(otherList[core.$get](dart.notNull(otherStart) + dart.notNull(i)), E));
+            this.set(dart.notNull(start) + dart.notNull(i), dart.as(otherList[dartx.get](dart.notNull(otherStart) + dart.notNull(i)), E));
           }
         }
       }
-      [core.$replaceRange](start, end, newContents) {
+      replaceRange(start, end, newContents) {
         dart.as(newContents, core.Iterable$(E));
-        core.RangeError.checkValidRange(start, end, this[core.$length]);
+        core.RangeError.checkValidRange(start, end, this.length);
         if (!dart.is(newContents, _internal.EfficientLength)) {
-          newContents = newContents[core.$toList]();
+          newContents = newContents[dartx.toList]();
         }
         let removeLength = dart.notNull(end) - dart.notNull(start);
-        let insertLength = newContents[core.$length];
+        let insertLength = newContents.length;
         if (dart.notNull(removeLength) >= dart.notNull(insertLength)) {
           let delta = dart.notNull(removeLength) - dart.notNull(insertLength);
           let insertEnd = dart.notNull(start) + dart.notNull(insertLength);
-          let newLength = dart.notNull(this[core.$length]) - dart.notNull(delta);
-          this[core.$setRange](start, insertEnd, newContents);
+          let newLength = dart.notNull(this.length) - dart.notNull(delta);
+          this.setRange(start, insertEnd, newContents);
           if (delta != 0) {
-            this[core.$setRange](insertEnd, newLength, this, end);
-            this[core.$length] = newLength;
+            this.setRange(insertEnd, newLength, this, end);
+            this.length = newLength;
           }
         } else {
           let delta = dart.notNull(insertLength) - dart.notNull(removeLength);
-          let newLength = dart.notNull(this[core.$length]) + dart.notNull(delta);
+          let newLength = dart.notNull(this.length) + dart.notNull(delta);
           let insertEnd = dart.notNull(start) + dart.notNull(insertLength);
-          this[core.$length] = newLength;
-          this[core.$setRange](insertEnd, newLength, this, end);
-          this[core.$setRange](start, insertEnd, newContents);
+          this.length = newLength;
+          this.setRange(insertEnd, newLength, this, end);
+          this.setRange(start, insertEnd, newContents);
         }
       }
-      [core.$indexOf](element, startIndex) {
+      indexOf(element, startIndex) {
         if (startIndex === void 0)
           startIndex = 0;
-        if (dart.notNull(startIndex) >= dart.notNull(this[core.$length])) {
+        if (dart.notNull(startIndex) >= dart.notNull(this.length)) {
           return -1;
         }
         if (dart.notNull(startIndex) < 0) {
           startIndex = 0;
         }
-        for (let i = startIndex; dart.notNull(i) < dart.notNull(this[core.$length]); i = dart.notNull(i) + 1) {
-          if (dart.equals(this[core.$get](i), element)) {
+        for (let i = startIndex; dart.notNull(i) < dart.notNull(this.length); i = dart.notNull(i) + 1) {
+          if (dart.equals(this.get(i), element)) {
             return i;
           }
         }
         return -1;
       }
-      [core.$lastIndexOf](element, startIndex) {
+      lastIndexOf(element, startIndex) {
         if (startIndex === void 0)
           startIndex = null;
         if (startIndex == null) {
-          startIndex = dart.notNull(this[core.$length]) - 1;
+          startIndex = dart.notNull(this.length) - 1;
         } else {
           if (dart.notNull(startIndex) < 0) {
             return -1;
           }
-          if (dart.notNull(startIndex) >= dart.notNull(this[core.$length])) {
-            startIndex = dart.notNull(this[core.$length]) - 1;
+          if (dart.notNull(startIndex) >= dart.notNull(this.length)) {
+            startIndex = dart.notNull(this.length) - 1;
           }
         }
         for (let i = startIndex; dart.notNull(i) >= 0; i = dart.notNull(i) - 1) {
-          if (dart.equals(this[core.$get](i), element)) {
+          if (dart.equals(this.get(i), element)) {
             return i;
           }
         }
         return -1;
       }
-      [core.$insert](index, element) {
+      insert(index, element) {
         dart.as(element, E);
-        core.RangeError.checkValueInInterval(index, 0, this[core.$length], "index");
-        if (index == this[core.$length]) {
-          this[core.$add](element);
+        core.RangeError.checkValueInInterval(index, 0, this.length, "index");
+        if (index == this.length) {
+          this.add(element);
           return;
         }
         if (!(typeof index == 'number'))
           throw new core.ArgumentError(index);
-        this[core.$length] = dart.notNull(this[core.$length]) + 1;
-        this[core.$setRange](dart.notNull(index) + 1, this[core.$length], this, index);
-        this[core.$set](index, element);
+        this.length = dart.notNull(this.length) + 1;
+        this.setRange(dart.notNull(index) + 1, this.length, this, index);
+        this.set(index, element);
       }
-      [core.$removeAt](index) {
-        let result = this[core.$get](index);
-        this[core.$setRange](index, dart.notNull(this[core.$length]) - 1, this, dart.notNull(index) + 1);
-        this[core.$length] = dart.notNull(this[core.$length]) - 1;
+      removeAt(index) {
+        let result = this.get(index);
+        this.setRange(index, dart.notNull(this.length) - 1, this, dart.notNull(index) + 1);
+        this.length = dart.notNull(this.length) - 1;
         return result;
       }
-      [core.$insertAll](index, iterable) {
+      insertAll(index, iterable) {
         dart.as(iterable, core.Iterable$(E));
-        core.RangeError.checkValueInInterval(index, 0, this[core.$length], "index");
+        core.RangeError.checkValueInInterval(index, 0, this.length, "index");
         if (dart.is(iterable, _internal.EfficientLength)) {
-          iterable = iterable[core.$toList]();
+          iterable = iterable[dartx.toList]();
         }
-        let insertionLength = iterable[core.$length];
-        this[core.$length] = dart.notNull(this[core.$length]) + dart.notNull(insertionLength);
-        this[core.$setRange](dart.notNull(index) + dart.notNull(insertionLength), this[core.$length], this, index);
-        this[core.$setAll](index, iterable);
+        let insertionLength = iterable.length;
+        this.length = dart.notNull(this.length) + dart.notNull(insertionLength);
+        this.setRange(dart.notNull(index) + dart.notNull(insertionLength), this.length, this, index);
+        this.setAll(index, iterable);
       }
-      [core.$setAll](index, iterable) {
+      setAll(index, iterable) {
         dart.as(iterable, core.Iterable$(E));
         if (dart.is(iterable, core.List)) {
-          this[core.$setRange](index, dart.notNull(index) + dart.notNull(iterable[core.$length]), iterable);
+          this.setRange(index, dart.notNull(index) + dart.notNull(iterable.length), iterable);
         } else {
           for (let element of iterable) {
-            this[core.$set]((() => {
+            this.set((() => {
               let x = index;
               index = dart.notNull(x) + 1;
               return x;
             })(), element);
           }
         }
       }
-      get [core.$reversed]() {
+      get reversed() {
         return new (_internal.ReversedListIterable$(E))(this);
       }
-      [core.$toString]() {
+      toString() {
         return IterableBase.iterableToFullString(this, '[', ']');
       }
     }
     ListMixin[dart.implements] = () => [core.List$(E)];
+    dart.implementExtension(ListMixin, () => [core.List, core.Iterable]);
     dart.setSignature(ListMixin, {
       methods: () => ({
-        [core.$elementAt]: [E, [core.int]],
-        [core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]],
-        [core.$contains]: [core.bool, [core.Object]],
-        [core.$every]: [core.bool, [dart.functionType(core.bool, [E])]],
-        [core.$any]: [core.bool, [dart.functionType(core.bool, [E])]],
-        [core.$firstWhere]: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
-        [core.$lastWhere]: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
-        [core.$singleWhere]: [E, [dart.functionType(core.bool, [E])]],
-        [core.$join]: [core.String, [], [core.String]],
-        [core.$where]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$map]: [core.Iterable, [dart.functionType(core.Object, [E])]],
-        [core.$expand]: [core.Iterable, [dart.functionType(core.Iterable, [E])]],
-        [core.$reduce]: [E, [dart.functionType(E, [E, E])]],
-        [core.$fold]: [core.Object, [core.Object, dart.functionType(core.Object, [dart.bottom, E])]],
-        [core.$skip]: [core.Iterable$(E), [core.int]],
-        [core.$skipWhile]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$take]: [core.Iterable$(E), [core.int]],
-        [core.$takeWhile]: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
-        [core.$toList]: [core.List$(E), [], {growable: core.bool}],
-        [core.$toSet]: [core.Set$(E), []],
-        [core.$add]: [dart.void, [E]],
-        [core.$addAll]: [dart.void, [core.Iterable$(E)]],
-        [core.$remove]: [core.bool, [core.Object]],
-        [core.$removeWhere]: [dart.void, [dart.functionType(core.bool, [E])]],
-        [core.$retainWhere]: [dart.void, [dart.functionType(core.bool, [E])]],
-        [core.$clear]: [dart.void, []],
-        [core.$removeLast]: [E, []],
-        [core.$sort]: [dart.void, [], [dart.functionType(core.int, [E, E])]],
-        [core.$shuffle]: [dart.void, [], [math.Random]],
-        [core.$asMap]: [core.Map$(core.int, E), []],
-        [core.$sublist]: [core.List$(E), [core.int], [core.int]],
-        [core.$getRange]: [core.Iterable$(E), [core.int, core.int]],
-        [core.$removeRange]: [dart.void, [core.int, core.int]],
-        [core.$fillRange]: [dart.void, [core.int, core.int], [E]],
-        [core.$setRange]: [dart.void, [core.int, core.int, core.Iterable$(E)], [core.int]],
-        [core.$replaceRange]: [dart.void, [core.int, core.int, core.Iterable$(E)]],
-        [core.$indexOf]: [core.int, [core.Object], [core.int]],
-        [core.$lastIndexOf]: [core.int, [core.Object], [core.int]],
-        [core.$insert]: [dart.void, [core.int, E]],
-        [core.$removeAt]: [E, [core.int]],
-        [core.$insertAll]: [dart.void, [core.int, core.Iterable$(E)]],
-        [core.$setAll]: [dart.void, [core.int, core.Iterable$(E)]]
+        elementAt: [E, [core.int]],
+        forEach: [dart.void, [dart.functionType(dart.void, [E])]],
+        contains: [core.bool, [core.Object]],
+        every: [core.bool, [dart.functionType(core.bool, [E])]],
+        any: [core.bool, [dart.functionType(core.bool, [E])]],
+        firstWhere: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
+        lastWhere: [E, [dart.functionType(core.bool, [E])], {orElse: dart.functionType(E, [])}],
+        singleWhere: [E, [dart.functionType(core.bool, [E])]],
+        join: [core.String, [], [core.String]],
+        where: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        map: [core.Iterable, [dart.functionType(core.Object, [E])]],
+        expand: [core.Iterable, [dart.functionType(core.Iterable, [E])]],
+        reduce: [E, [dart.functionType(E, [E, E])]],
+        fold: [core.Object, [core.Object, dart.functionType(core.Object, [dart.bottom, E])]],
+        skip: [core.Iterable$(E), [core.int]],
+        skipWhile: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        take: [core.Iterable$(E), [core.int]],
+        takeWhile: [core.Iterable$(E), [dart.functionType(core.bool, [E])]],
+        toList: [core.List$(E), [], {growable: core.bool}],
+        toSet: [core.Set$(E), []],
+        add: [dart.void, [E]],
+        addAll: [dart.void, [core.Iterable$(E)]],
+        remove: [core.bool, [core.Object]],
+        removeWhere: [dart.void, [dart.functionType(core.bool, [E])]],
+        retainWhere: [dart.void, [dart.functionType(core.bool, [E])]],
+        clear: [dart.void, []],
+        removeLast: [E, []],
+        sort: [dart.void, [], [dart.functionType(core.int, [E, E])]],
+        shuffle: [dart.void, [], [math.Random]],
+        asMap: [core.Map$(core.int, E), []],
+        sublist: [core.List$(E), [core.int], [core.int]],
+        getRange: [core.Iterable$(E), [core.int, core.int]],
+        removeRange: [dart.void, [core.int, core.int]],
+        fillRange: [dart.void, [core.int, core.int], [E]],
+        setRange: [dart.void, [core.int, core.int, core.Iterable$(E)], [core.int]],
+        replaceRange: [dart.void, [core.int, core.int, core.Iterable$(E)]],
+        indexOf: [core.int, [core.Object], [core.int]],
+        lastIndexOf: [core.int, [core.Object], [core.int]],
+        insert: [dart.void, [core.int, E]],
+        removeAt: [E, [core.int]],
+        insertAll: [dart.void, [core.int, core.Iterable$(E)]],
+        setAll: [dart.void, [core.int, core.Iterable$(E)]]
       }),
       statics: () => ({_filter: [dart.void, [core.List, dart.functionType(core.bool, [dart.bottom]), core.bool]]}),
       names: ['_filter']
     });
     return ListMixin;
   });
   let ListMixin = ListMixin$();
   let ListBase$ = dart.generic(function(E) {
     class ListBase extends dart.mixin(core.Object, ListMixin$(E)) {
       static listToString(list) {
@@ skipping 24 matching lines @@
       containsValue(value) {
         for (let key of this.keys) {
           if (dart.equals(this.get(key), value))
             return true;
         }
         return false;
       }
       putIfAbsent(key, ifAbsent) {
         dart.as(key, K);
         dart.as(ifAbsent, dart.functionType(V, []));
-        if (this.keys[core.$contains](key)) {
+        if (this.keys[dartx.contains](key)) {
           return this.get(key);
         }
         return this.set(key, ifAbsent());
       }
       containsKey(key) {
-        return this.keys[core.$contains](key);
+        return this.keys[dartx.contains](key);
       }
       get length() {
-        return this.keys[core.$length];
+        return this.keys.length;
       }
       get isEmpty() {
-        return this.keys[core.$isEmpty];
+        return this.keys[dartx.isEmpty];
       }
       get isNotEmpty() {
-        return this.keys[core.$isNotEmpty];
+        return this.keys[dartx.isNotEmpty];
       }
       get values() {
         return new (_MapBaseValueIterable$(V))(this);
       }
       toString() {
         return Maps.mapToString(this);
       }
     }
     MapMixin[dart.implements] = () => [core.Map$(K, V)];
     dart.setSignature(MapMixin, {
@@ skipping 54 matching lines @@
     return UnmodifiableMapBase;
   });
   let UnmodifiableMapBase = UnmodifiableMapBase$();
   let _map = Symbol('_map');
   let _MapBaseValueIterable$ = dart.generic(function(V) {
     class _MapBaseValueIterable extends IterableBase$(V) {
       _MapBaseValueIterable(map) {
         this[_map] = map;
         super.IterableBase();
       }
-      get [core.$length]() {
+      get length() {
         return this[_map].length;
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return this[_map].isEmpty;
       }
-      get [core.$isNotEmpty]() {
+      get isNotEmpty() {
         return this[_map].isNotEmpty;
       }
-      get [core.$first]() {
-        return dart.as(this[_map].get(this[_map].keys[core.$first]), V);
+      get first() {
+        return dart.as(this[_map].get(this[_map].keys[dartx.first]), V);
       }
-      get [core.$single]() {
-        return dart.as(this[_map].get(this[_map].keys[core.$single]), V);
+      get single() {
+        return dart.as(this[_map].get(this[_map].keys[dartx.single]), V);
       }
-      get [core.$last]() {
-        return dart.as(this[_map].get(this[_map].keys[core.$last]), V);
+      get last() {
+        return dart.as(this[_map].get(this[_map].keys[dartx.last]), V);
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (_MapBaseValueIterator$(V))(this[_map]);
       }
     }
     _MapBaseValueIterable[dart.implements] = () => [_internal.EfficientLength];
+    dart.implementExtension(_MapBaseValueIterable, () => [core.Iterable]);
     dart.setSignature(_MapBaseValueIterable, {
       constructors: () => ({_MapBaseValueIterable: [_MapBaseValueIterable$(V), [core.Map]]})
     });
     return _MapBaseValueIterable;
   });
   let _MapBaseValueIterable = _MapBaseValueIterable$();
   let _keys = Symbol('_keys');
   let _MapBaseValueIterator$ = dart.generic(function(V) {
     class _MapBaseValueIterator extends core.Object {
       _MapBaseValueIterator(map) {
         this[_map] = map;
-        this[_keys] = map.keys[core.$iterator];
+        this[_keys] = map.keys[dartx.iterator];
         this[_current] = null;
       }
       moveNext() {
         if (this[_keys].moveNext()) {
           this[_current] = dart.as(this[_map].get(this[_keys].current), V);
           return true;
         }
         this[_current] = null;
         return false;
       }
@@ skipping 108 matching lines @@
     }
     static putIfAbsent(map, key, ifAbsent) {
       if (map.containsKey(key)) {
         return map.get(key);
       }
       let v = ifAbsent();
       map.set(key, v);
       return v;
     }
     static clear(map) {
-      for (let k of map.keys[core.$toList]()) {
+      for (let k of map.keys[dartx.toList]()) {
         map.remove(k);
       }
     }
     static forEach(map, f) {
       for (let k of map.keys) {
         dart.dcall(f, k, map.get(k));
       }
     }
     static getValues(map) {
-      return map.keys[core.$map](dart.fn(key => map.get(key)));
+      return map.keys[dartx.map](dart.fn(key => map.get(key)));
     }
     static length(map) {
-      return map.keys[core.$length];
+      return map.keys.length;
     }
     static isEmpty(map) {
-      return map.keys[core.$isEmpty];
+      return map.keys[dartx.isEmpty];
     }
     static isNotEmpty(map) {
-      return map.keys[core.$isNotEmpty];
+      return map.keys[dartx.isNotEmpty];
     }
     static mapToString(m) {
       if (IterableBase._isToStringVisiting(m)) {
         return '{...}';
       }
       let result = new core.StringBuffer();
       try {
-        IterableBase._toStringVisiting[core.$add](m);
+        IterableBase._toStringVisiting[dartx.add](m);
         result.write('{');
         let first = true;
         m.forEach(dart.fn((k, v) => {
           if (!dart.notNull(first)) {
             result.write(', ');
           }
           first = false;
           result.write(k);
           result.write(': ');
           result.write(v);
         }));
         result.write('}');
       } finally {
-        dart.assert(core.identical(IterableBase._toStringVisiting[core.$last], m));
-        IterableBase._toStringVisiting[core.$removeLast]();
+        dart.assert(core.identical(IterableBase._toStringVisiting[dartx.last], m));
+        IterableBase._toStringVisiting[dartx.removeLast]();
       }
       return dart.toString(result);
     }
     static _id(x) {
       return x;
     }
     static _fillMapWithMappedIterable(map, iterable, key, value) {
       if (key == null)
         key = Maps._id;
       if (value == null)
         value = Maps._id;
       for (let element of iterable) {
         map.set(dart.dcall(key, element), dart.dcall(value, element));
       }
     }
     static _fillMapWithIterables(map, keys, values) {
-      let keyIterator = keys[core.$iterator];
-      let valueIterator = values[core.$iterator];
+      let keyIterator = keys[dartx.iterator];
+      let valueIterator = values[dartx.iterator];
       let hasNextKey = keyIterator.moveNext();
       let hasNextValue = valueIterator.moveNext();
       while (dart.notNull(hasNextKey) && dart.notNull(hasNextValue)) {
         map.set(keyIterator.current, valueIterator.current);
         hasNextKey = keyIterator.moveNext();
         hasNextValue = valueIterator.moveNext();
       }
       if (dart.notNull(hasNextKey) || dart.notNull(hasNextValue)) {
         throw new core.ArgumentError("Iterables do not have same length.");
       }
@@ skipping 19 matching lines @@
   });
   let Queue$ = dart.generic(function(E) {
     class Queue extends core.Object {
       static new() {
         return new (ListQueue$(E))();
       }
       static from(elements) {
         return ListQueue$(E).from(elements);
       }
       [Symbol.iterator]() {
-        return new dart.JsIterator(this[core.$iterator]);
+        return new dart.JsIterator(this.iterator);
       }
     }
     Queue[dart.implements] = () => [core.Iterable$(E), _internal.EfficientLength];
+    dart.implementExtension(Queue, () => [core.Iterable]);
     dart.setSignature(Queue, {
       constructors: () => ({
         new: [Queue$(E), []],
         from: [Queue$(E), [core.Iterable]]
       })
     });
     return Queue;
   });
   let Queue = Queue$();
   let _element = Symbol('_element');
@@ skipping 102 matching lines @@
         super.IterableBase();
         this[_sentinel] = new (_DoubleLinkedQueueEntrySentinel$(E))();
       }
       static from(elements) {
         let list = new (DoubleLinkedQueue$(E))();
         for (let e of dart.as(elements, core.Iterable$(E))) {
           list.addLast(e);
         }
         return dart.as(list, DoubleLinkedQueue$(E));
       }
-      get [core.$length]() {
+      get length() {
         return this[_elementCount];
       }
       addLast(value) {
         dart.as(value, E);
         this[_sentinel].prepend(value);
         this[_elementCount] = dart.notNull(this[_elementCount]) + 1;
       }
       addFirst(value) {
         dart.as(value, E);
         this[_sentinel].append(value);
@@ skipping 46 matching lines @@
         }
       }
       removeWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         this[_filter](test, true);
       }
       retainWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         this[_filter](test, false);
       }
-      get [core.$first]() {
+      get first() {
         return this[_sentinel][_next].element;
       }
-      get [core.$last]() {
+      get last() {
         return this[_sentinel][_previous].element;
       }
-      get [core.$single]() {
+      get single() {
         if (core.identical(this[_sentinel][_next], this[_sentinel][_previous])) {
           return this[_sentinel][_next].element;
         }
         throw _internal.IterableElementError.tooMany();
       }
       lastEntry() {
         return this[_sentinel].previousEntry();
       }
       firstEntry() {
         return this[_sentinel].nextEntry();
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return core.identical(this[_sentinel][_next], this[_sentinel]);
       }
       clear() {
         this[_sentinel][_next] = this[_sentinel];
         this[_sentinel][_previous] = this[_sentinel];
         this[_elementCount] = 0;
       }
       forEachEntry(f) {
         dart.as(f, dart.functionType(dart.void, [DoubleLinkedQueueEntry$(E)]));
         let entry = this[_sentinel][_next];
         while (!dart.notNull(core.identical(entry, this[_sentinel]))) {
           let nextEntry = entry[_next];
           f(entry);
           entry = nextEntry;
         }
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (_DoubleLinkedQueueIterator$(E))(this[_sentinel]);
       }
       toString() {
         return IterableBase.iterableToFullString(this, '{', '}');
       }
     }
     DoubleLinkedQueue[dart.implements] = () => [Queue$(E)];
+    dart.implementExtension(DoubleLinkedQueue, () => [core.Iterable]);
     dart.setSignature(DoubleLinkedQueue, {
       constructors: () => ({
         DoubleLinkedQueue: [DoubleLinkedQueue$(E), []],
         from: [DoubleLinkedQueue$(E), [core.Iterable]]
       }),
       methods: () => ({
         addLast: [dart.void, [E]],
         addFirst: [dart.void, [E]],
         add: [dart.void, [E]],
         addAll: [dart.void, [core.Iterable$(E)]],
@@ skipping 65 matching lines @@
         if (initialCapacity == null || dart.notNull(initialCapacity) < dart.notNull(ListQueue$()._INITIAL_CAPACITY)) {
           initialCapacity = ListQueue$()._INITIAL_CAPACITY;
         } else if (!dart.notNull(ListQueue$()._isPowerOf2(initialCapacity))) {
           initialCapacity = ListQueue$()._nextPowerOf2(initialCapacity);
         }
         dart.assert(ListQueue$()._isPowerOf2(initialCapacity));
         this[_table] = core.List$(E).new(initialCapacity);
       }
       static from(elements) {
         if (dart.is(elements, core.List)) {
-          let length = elements[core.$length];
+          let length = elements.length;
           let queue = new (ListQueue$(E))(dart.notNull(length) + 1);
-          dart.assert(dart.notNull(queue[_table][core.$length]) > dart.notNull(length));
+          dart.assert(dart.notNull(queue[_table].length) > dart.notNull(length));
           let sourceList = elements;
-          queue[_table][core.$setRange](0, length, dart.as(sourceList, core.Iterable$(E)), 0);
+          queue[_table][dartx.setRange](0, length, dart.as(sourceList, core.Iterable$(E)), 0);
           queue[_tail] = length;
           return queue;
         } else {
           let capacity = ListQueue$()._INITIAL_CAPACITY;
           if (dart.is(elements, _internal.EfficientLength)) {
-            capacity = elements[core.$length];
+            capacity = elements.length;
           }
           let result = new (ListQueue$(E))(capacity);
           for (let element of dart.as(elements, core.Iterable$(E))) {
             result.addLast(element);
           }
           return result;
         }
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (_ListQueueIterator$(E))(this);
       }
-      [core.$forEach](action) {
+      forEach(action) {
         dart.as(action, dart.functionType(dart.void, [E]));
         let modificationCount = this[_modificationCount];
-        for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table][core.$length]) - 1) {
-          action(this[_table][core.$get](i));
+        for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table].length) - 1) {
+          action(this[_table][dartx.get](i));
           this[_checkModification](modificationCount);
         }
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return this[_head] == this[_tail];
       }
-      get [core.$length]() {
-        return dart.notNull(this[_tail]) - dart.notNull(this[_head]) & dart.notNull(this[_table][core.$length]) - 1;
+      get length() {
+        return dart.notNull(this[_tail]) - dart.notNull(this[_head]) & dart.notNull(this[_table].length) - 1;
       }
-      get [core.$first]() {
+      get first() {
         if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
-        return this[_table][core.$get](this[_head]);
+        return this[_table][dartx.get](this[_head]);
       }
-      get [core.$last]() {
+      get last() {
         if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
-        return this[_table][core.$get](dart.notNull(this[_tail]) - 1 & dart.notNull(this[_table][core.$length]) - 1);
+        return this[_table][dartx.get](dart.notNull(this[_tail]) - 1 & dart.notNull(this[_table].length) - 1);
       }
-      get [core.$single]() {
+      get single() {
         if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
-        if (dart.notNull(this[core.$length]) > 1)
+        if (dart.notNull(this.length) > 1)
           throw _internal.IterableElementError.tooMany();
-        return this[_table][core.$get](this[_head]);
+        return this[_table][dartx.get](this[_head]);
       }
-      [core.$elementAt](index) {
+      elementAt(index) {
         core.RangeError.checkValidIndex(index, this);
-        return this[_table][core.$get](dart.notNull(this[_head]) + dart.notNull(index) & dart.notNull(this[_table][core.$length]) - 1);
+        return this[_table][dartx.get](dart.notNull(this[_head]) + dart.notNull(index) & dart.notNull(this[_table].length) - 1);
       }
-      [core.$toList](opts) {
+      toList(opts) {
         let growable = opts && 'growable' in opts ? opts.growable : true;
         let list = null;
         if (growable) {
           list = core.List$(E).new();
-          list[core.$length] = this[core.$length];
+          list.length = this.length;
         } else {
-          list = core.List$(E).new(this[core.$length]);
+          list = core.List$(E).new(this.length);
         }
         this[_writeToList](list);
         return list;
       }
       add(element) {
         dart.as(element, E);
         this[_add](element);
       }
       addAll(elements) {
         dart.as(elements, core.Iterable$(E));
         if (dart.is(elements, core.List)) {
           let list = dart.as(elements, core.List);
-          let addCount = list[core.$length];
-          let length = this[core.$length];
-          if (dart.notNull(length) + dart.notNull(addCount) >= dart.notNull(this[_table][core.$length])) {
+          let addCount = list.length;
+          let length = this.length;
+          if (dart.notNull(length) + dart.notNull(addCount) >= dart.notNull(this[_table].length)) {
             this[_preGrow](dart.notNull(length) + dart.notNull(addCount));
-            this[_table][core.$setRange](length, dart.notNull(length) + dart.notNull(addCount), dart.as(list, core.Iterable$(E)), 0);
+            this[_table][dartx.setRange](length, dart.notNull(length) + dart.notNull(addCount), dart.as(list, core.Iterable$(E)), 0);
             this[_tail] = dart.notNull(this[_tail]) + dart.notNull(addCount);
           } else {
-            let endSpace = dart.notNull(this[_table][core.$length]) - dart.notNull(this[_tail]);
+            let endSpace = dart.notNull(this[_table].length) - dart.notNull(this[_tail]);
             if (dart.notNull(addCount) < dart.notNull(endSpace)) {
-              this[_table][core.$setRange](this[_tail], dart.notNull(this[_tail]) + dart.notNull(addCount), dart.as(list, core.Iterable$(E)), 0);
+              this[_table][dartx.setRange](this[_tail], dart.notNull(this[_tail]) + dart.notNull(addCount), dart.as(list, core.Iterable$(E)), 0);
               this[_tail] = dart.notNull(this[_tail]) + dart.notNull(addCount);
             } else {
               let preSpace = dart.notNull(addCount) - dart.notNull(endSpace);
-              this[_table][core.$setRange](this[_tail], dart.notNull(this[_tail]) + dart.notNull(endSpace), dart.as(list, core.Iterable$(E)), 0);
-              this[_table][core.$setRange](0, preSpace, dart.as(list, core.Iterable$(E)), endSpace);
+              this[_table][dartx.setRange](this[_tail], dart.notNull(this[_tail]) + dart.notNull(endSpace), dart.as(list, core.Iterable$(E)), 0);
+              this[_table][dartx.setRange](0, preSpace, dart.as(list, core.Iterable$(E)), endSpace);
               this[_tail] = preSpace;
             }
           }
           this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         } else {
           for (let element of elements)
             this[_add](element);
         }
       }
       remove(object) {
-        for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table][core.$length]) - 1) {
-          let element = this[_table][core.$get](i);
+        for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table].length) - 1) {
+          let element = this[_table][dartx.get](i);
           if (dart.equals(element, object)) {
             this[_remove](i);
             this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
             return true;
           }
         }
         return false;
       }
       [_filterWhere](test, removeMatching) {
         dart.as(test, dart.functionType(core.bool, [E]));
         let index = this[_head];
         let modificationCount = this[_modificationCount];
         let i = this[_head];
         while (i != this[_tail]) {
-          let element = this[_table][core.$get](i);
+          let element = this[_table][dartx.get](i);
           let remove = core.identical(removeMatching, test(element));
           this[_checkModification](modificationCount);
           if (remove) {
             i = this[_remove](i);
             modificationCount = this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
           } else {
-            i = dart.notNull(i) + 1 & dart.notNull(this[_table][core.$length]) - 1;
+            i = dart.notNull(i) + 1 & dart.notNull(this[_table].length) - 1;
           }
         }
       }
       removeWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         this[_filterWhere](test, true);
       }
       retainWhere(test) {
         dart.as(test, dart.functionType(core.bool, [E]));
         this[_filterWhere](test, false);
       }
       clear() {
         if (this[_head] != this[_tail]) {
-          for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table][core.$length]) - 1) {
-            this[_table][core.$set](i, null);
+          for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table].length) - 1) {
+            this[_table][dartx.set](i, null);
           }
           this[_head] = this[_tail] = 0;
           this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         }
       }
       toString() {
         return IterableBase.iterableToFullString(this, "{", "}");
       }
       addLast(element) {
         dart.as(element, E);
         this[_add](element);
       }
       addFirst(element) {
         dart.as(element, E);
-        this[_head] = dart.notNull(this[_head]) - 1 & dart.notNull(this[_table][core.$length]) - 1;
-        this[_table][core.$set](this[_head], element);
+        this[_head] = dart.notNull(this[_head]) - 1 & dart.notNull(this[_table].length) - 1;
+        this[_table][dartx.set](this[_head], element);
         if (this[_head] == this[_tail])
           this[_grow]();
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
       }
       removeFirst() {
         if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
-        let result = this[_table][core.$get](this[_head]);
-        this[_table][core.$set](this[_head], null);
-        this[_head] = dart.notNull(this[_head]) + 1 & dart.notNull(this[_table][core.$length]) - 1;
+        let result = this[_table][dartx.get](this[_head]);
+        this[_table][dartx.set](this[_head], null);
+        this[_head] = dart.notNull(this[_head]) + 1 & dart.notNull(this[_table].length) - 1;
         return result;
       }
       removeLast() {
         if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
-        this[_tail] = dart.notNull(this[_tail]) - 1 & dart.notNull(this[_table][core.$length]) - 1;
-        let result = this[_table][core.$get](this[_tail]);
-        this[_table][core.$set](this[_tail], null);
+        this[_tail] = dart.notNull(this[_tail]) - 1 & dart.notNull(this[_table].length) - 1;
+        let result = this[_table][dartx.get](this[_tail]);
+        this[_table][dartx.set](this[_tail], null);
         return result;
       }
       static _isPowerOf2(number) {
         return (dart.notNull(number) & dart.notNull(number) - 1) == 0;
       }
       static _nextPowerOf2(number) {
         dart.assert(dart.notNull(number) > 0);
         number = (dart.notNull(number) << 1) - 1;
         for (;;) {
           let nextNumber = dart.notNull(number) & dart.notNull(number) - 1;
           if (nextNumber == 0)
             return number;
           number = nextNumber;
         }
       }
       [_checkModification](expectedModificationCount) {
         if (expectedModificationCount != this[_modificationCount]) {
           throw new core.ConcurrentModificationError(this);
         }
       }
       [_add](element) {
         dart.as(element, E);
-        this[_table][core.$set](this[_tail], element);
-        this[_tail] = dart.notNull(this[_tail]) + 1 & dart.notNull(this[_table][core.$length]) - 1;
+        this[_table][dartx.set](this[_tail], element);
+        this[_tail] = dart.notNull(this[_tail]) + 1 & dart.notNull(this[_table].length) - 1;
         if (this[_head] == this[_tail])
           this[_grow]();
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
       }
       [_remove](offset) {
-        let mask = dart.notNull(this[_table][core.$length]) - 1;
+        let mask = dart.notNull(this[_table].length) - 1;
         let startDistance = dart.notNull(offset) - dart.notNull(this[_head]) & dart.notNull(mask);
         let endDistance = dart.notNull(this[_tail]) - dart.notNull(offset) & dart.notNull(mask);
         if (dart.notNull(startDistance) < dart.notNull(endDistance)) {
           let i = offset;
           while (i != this[_head]) {
             let prevOffset = dart.notNull(i) - 1 & dart.notNull(mask);
-            this[_table][core.$set](i, this[_table][core.$get](prevOffset));
+            this[_table][dartx.set](i, this[_table][dartx.get](prevOffset));
             i = prevOffset;
           }
-          this[_table][core.$set](this[_head], null);
+          this[_table][dartx.set](this[_head], null);
           this[_head] = dart.notNull(this[_head]) + 1 & dart.notNull(mask);
           return dart.notNull(offset) + 1 & dart.notNull(mask);
         } else {
           this[_tail] = dart.notNull(this[_tail]) - 1 & dart.notNull(mask);
           let i = offset;
           while (i != this[_tail]) {
             let nextOffset = dart.notNull(i) + 1 & dart.notNull(mask);
-            this[_table][core.$set](i, this[_table][core.$get](nextOffset));
+            this[_table][dartx.set](i, this[_table][dartx.get](nextOffset));
             i = nextOffset;
           }
-          this[_table][core.$set](this[_tail], null);
+          this[_table][dartx.set](this[_tail], null);
           return offset;
         }
       }
       [_grow]() {
-        let newTable = core.List$(E).new(dart.notNull(this[_table][core.$length]) * 2);
-        let split = dart.notNull(this[_table][core.$length]) - dart.notNull(this[_head]);
-        newTable[core.$setRange](0, split, this[_table], this[_head]);
-        newTable[core.$setRange](split, dart.notNull(split) + dart.notNull(this[_head]), this[_table], 0);
+        let newTable = core.List$(E).new(dart.notNull(this[_table].length) * 2);
+        let split = dart.notNull(this[_table].length) - dart.notNull(this[_head]);
+        newTable[dartx.setRange](0, split, this[_table], this[_head]);
+        newTable[dartx.setRange](split, dart.notNull(split) + dart.notNull(this[_head]), this[_table], 0);
         this[_head] = 0;
-        this[_tail] = this[_table][core.$length];
+        this[_tail] = this[_table].length;
         this[_table] = newTable;
       }
       [_writeToList](target) {
         dart.as(target, core.List$(E));
-        dart.assert(dart.notNull(target[core.$length]) >= dart.notNull(this[core.$length]));
+        dart.assert(dart.notNull(target.length) >= dart.notNull(this.length));
         if (dart.notNull(this[_head]) <= dart.notNull(this[_tail])) {
           let length = dart.notNull(this[_tail]) - dart.notNull(this[_head]);
-          target[core.$setRange](0, length, this[_table], this[_head]);
+          target[dartx.setRange](0, length, this[_table], this[_head]);
           return length;
         } else {
-          let firstPartSize = dart.notNull(this[_table][core.$length]) - dart.notNull(this[_head]);
-          target[core.$setRange](0, firstPartSize, this[_table], this[_head]);
-          target[core.$setRange](firstPartSize, dart.notNull(firstPartSize) + dart.notNull(this[_tail]), this[_table], 0);
+          let firstPartSize = dart.notNull(this[_table].length) - dart.notNull(this[_head]);
+          target[dartx.setRange](0, firstPartSize, this[_table], this[_head]);
+          target[dartx.setRange](firstPartSize, dart.notNull(firstPartSize) + dart.notNull(this[_tail]), this[_table], 0);
           return dart.notNull(this[_tail]) + dart.notNull(firstPartSize);
         }
       }
       [_preGrow](newElementCount) {
-        dart.assert(dart.notNull(newElementCount) >= dart.notNull(this[core.$length]));
+        dart.assert(dart.notNull(newElementCount) >= dart.notNull(this.length));
         newElementCount = dart.notNull(newElementCount) + (dart.notNull(newElementCount) >> 1);
         let newCapacity = ListQueue$()._nextPowerOf2(newElementCount);
         let newTable = core.List$(E).new(newCapacity);
         this[_tail] = this[_writeToList](newTable);
         this[_table] = newTable;
         this[_head] = 0;
       }
     }
     ListQueue[dart.implements] = () => [Queue$(E)];
+    dart.implementExtension(ListQueue, () => [core.Iterable]);
     dart.setSignature(ListQueue, {
       constructors: () => ({
         ListQueue: [ListQueue$(E), [], [core.int]],
         from: [ListQueue$(E), [core.Iterable]]
       }),
       methods: () => ({
-        [core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]],
-        [core.$elementAt]: [E, [core.int]],
-        [core.$toList]: [core.List$(E), [], {growable: core.bool}],
+        forEach: [dart.void, [dart.functionType(dart.void, [E])]],
+        elementAt: [E, [core.int]],
+        toList: [core.List$(E), [], {growable: core.bool}],
         add: [dart.void, [E]],
         addAll: [dart.void, [core.Iterable$(E)]],
         remove: [core.bool, [core.Object]],
         [_filterWhere]: [dart.void, [dart.functionType(core.bool, [E]), core.bool]],
         removeWhere: [dart.void, [dart.functionType(core.bool, [E])]],
         retainWhere: [dart.void, [dart.functionType(core.bool, [E])]],
         clear: [dart.void, []],
         addLast: [dart.void, [E]],
         addFirst: [dart.void, [E]],
         removeFirst: [E, []],
@@ skipping 29 matching lines @@
       }
       get current() {
         return this[_current];
       }
       moveNext() {
         this[_queue][_checkModification](this[_modificationCount]);
         if (this[_position] == this[_end]) {
           this[_current] = null;
           return false;
         }
-        this[_current] = dart.as(this[_queue][_table][core.$get](this[_position]), E);
-        this[_position] = dart.notNull(this[_position]) + 1 & dart.notNull(this[_queue][_table][core.$length]) - 1;
+        this[_current] = dart.as(this[_queue][_table][dartx.get](this[_position]), E);
+        this[_position] = dart.notNull(this[_position]) + 1 & dart.notNull(this[_queue][_table].length) - 1;
         return true;
       }
     }
     _ListQueueIterator[dart.implements] = () => [core.Iterator$(E)];
     dart.setSignature(_ListQueueIterator, {
       constructors: () => ({_ListQueueIterator: [_ListQueueIterator$(E), [ListQueue]]}),
       methods: () => ({moveNext: [core.bool, []]})
     });
     return _ListQueueIterator;
   });
@@ skipping 442 matching lines @@
   let SplayTreeMap = SplayTreeMap$();
   let _workList = Symbol('_workList');
   let _tree = Symbol('_tree');
   let _currentNode = Symbol('_currentNode');
   let _findLeftMostDescendent = Symbol('_findLeftMostDescendent');
   let _getValue = Symbol('_getValue');
   let _rebuildWorkList = Symbol('_rebuildWorkList');
   let _SplayTreeIterator$ = dart.generic(function(T) {
     class _SplayTreeIterator extends core.Object {
       _SplayTreeIterator(tree) {
-        this[_workList] = dart.setType([], core.List$(_SplayTreeNode));
+        this[_workList] = dart.list([], _SplayTreeNode);
         this[_tree] = tree;
         this[_modificationCount] = tree[_modificationCount];
         this[_splayCount] = tree[_splayCount];
         this[_currentNode] = null;
         this[_findLeftMostDescendent](tree[_root]);
       }
       startAt(tree, startKey) {
-        this[_workList] = dart.setType([], core.List$(_SplayTreeNode));
+        this[_workList] = dart.list([], _SplayTreeNode);
         this[_tree] = tree;
         this[_modificationCount] = tree[_modificationCount];
         this[_splayCount] = null;
         this[_currentNode] = null;
         if (tree[_root] == null)
           return;
         let compare = tree[_splay](startKey);
         this[_splayCount] = tree[_splayCount];
         if (dart.notNull(compare) < 0) {
           this[_findLeftMostDescendent](tree[_root].right);
         } else {
-          this[_workList][core.$add](tree[_root]);
+          this[_workList][dartx.add](tree[_root]);
         }
       }
       get current() {
         if (this[_currentNode] == null)
           return null;
         return this[_getValue](dart.as(this[_currentNode], _SplayTreeMapNode));
       }
       [_findLeftMostDescendent](node) {
         while (node != null) {
-          this[_workList][core.$add](node);
+          this[_workList][dartx.add](node);
           node = node.left;
         }
       }
       [_rebuildWorkList](currentNode) {
-        dart.assert(!dart.notNull(this[_workList][core.$isEmpty]));
-        this[_workList][core.$clear]();
+        dart.assert(!dart.notNull(this[_workList][dartx.isEmpty]));
+        this[_workList][dartx.clear]();
         if (currentNode == null) {
           this[_findLeftMostDescendent](this[_tree][_root]);
         } else {
           this[_tree][_splay](currentNode.key);
           this[_findLeftMostDescendent](this[_tree][_root].right);
-          dart.assert(!dart.notNull(this[_workList][core.$isEmpty]));
+          dart.assert(!dart.notNull(this[_workList][dartx.isEmpty]));
         }
       }
       moveNext() {
         if (this[_modificationCount] != this[_tree][_modificationCount]) {
           throw new core.ConcurrentModificationError(this[_tree]);
         }
-        if (this[_workList][core.$isEmpty]) {
+        if (this[_workList][dartx.isEmpty]) {
           this[_currentNode] = null;
           return false;
         }
         if (this[_tree][_splayCount] != this[_splayCount] && dart.notNull(this[_currentNode] != null)) {
           this[_rebuildWorkList](this[_currentNode]);
         }
-        this[_currentNode] = this[_workList][core.$removeLast]();
+        this[_currentNode] = this[_workList][dartx.removeLast]();
         this[_findLeftMostDescendent](this[_currentNode].right);
         return true;
       }
     }
     _SplayTreeIterator[dart.implements] = () => [core.Iterator$(T)];
     dart.defineNamedConstructor(_SplayTreeIterator, 'startAt');
     dart.setSignature(_SplayTreeIterator, {
       constructors: () => ({
         _SplayTreeIterator: [_SplayTreeIterator$(T), [_SplayTree]],
         startAt: [_SplayTreeIterator$(T), [_SplayTree, core.Object]]
       }),
       methods: () => ({
         [_findLeftMostDescendent]: [dart.void, [_SplayTreeNode]],
         [_rebuildWorkList]: [dart.void, [_SplayTreeNode]],
         moveNext: [core.bool, []]
       })
     });
     return _SplayTreeIterator;
   });
   let _SplayTreeIterator = _SplayTreeIterator$();
   let _copyNode = Symbol('_copyNode');
   let _SplayTreeKeyIterable$ = dart.generic(function(K) {
     class _SplayTreeKeyIterable extends IterableBase$(K) {
       _SplayTreeKeyIterable(tree) {
         this[_tree] = tree;
         super.IterableBase();
       }
-      get [core.$length]() {
+      get length() {
         return this[_tree][_count];
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return this[_tree][_count] == 0;
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (_SplayTreeKeyIterator$(K))(this[_tree]);
       }
-      [core.$toSet]() {
+      toSet() {
         let setOrMap = this[_tree];
         let set = new (SplayTreeSet$(K))(dart.as(setOrMap[_comparator], __CastType0), dart.as(setOrMap[_validKey], __CastType3));
         set[_count] = this[_tree][_count];
         set[_root] = set[_copyNode](this[_tree][_root]);
         return set;
       }
     }
     _SplayTreeKeyIterable[dart.implements] = () => [_internal.EfficientLength];
+    dart.implementExtension(_SplayTreeKeyIterable, () => [core.Iterable]);
     dart.setSignature(_SplayTreeKeyIterable, {
       constructors: () => ({_SplayTreeKeyIterable: [_SplayTreeKeyIterable$(K), [_SplayTree$(K)]]}),
-      methods: () => ({[core.$toSet]: [core.Set$(K), []]})
+      methods: () => ({toSet: [core.Set$(K), []]})
     });
     return _SplayTreeKeyIterable;
   });
   let _SplayTreeKeyIterable = _SplayTreeKeyIterable$();
   let _SplayTreeValueIterable$ = dart.generic(function(K, V) {
     class _SplayTreeValueIterable extends IterableBase$(V) {
       _SplayTreeValueIterable(map) {
         this[_map] = map;
         super.IterableBase();
       }
-      get [core.$length]() {
+      get length() {
         return this[_map][_count];
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return this[_map][_count] == 0;
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (_SplayTreeValueIterator$(K, V))(this[_map]);
       }
     }
     _SplayTreeValueIterable[dart.implements] = () => [_internal.EfficientLength];
+    dart.implementExtension(_SplayTreeValueIterable, () => [core.Iterable]);
     dart.setSignature(_SplayTreeValueIterable, {
       constructors: () => ({_SplayTreeValueIterable: [_SplayTreeValueIterable$(K, V), [SplayTreeMap$(K, V)]]})
     });
     return _SplayTreeValueIterable;
   });
   let _SplayTreeValueIterable = _SplayTreeValueIterable$();
   let _SplayTreeKeyIterator$ = dart.generic(function(K) {
     class _SplayTreeKeyIterator extends _SplayTreeIterator$(K) {
       _SplayTreeKeyIterator(map) {
         super._SplayTreeIterator(map);
@@ skipping 69 matching lines @@
         for (let element of dart.as(elements, core.Iterable$(E))) {
           result.add(element);
         }
         return result;
       }
       [_compare](e1, e2) {
         dart.as(e1, E);
         dart.as(e2, E);
         return this[_comparator](e1, e2);
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (_SplayTreeKeyIterator$(E))(this);
       }
-      get [core.$length]() {
+      get length() {
         return this[_count];
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return this[_root] == null;
       }
-      get [core.$isNotEmpty]() {
+      get isNotEmpty() {
         return this[_root] != null;
       }
-      get [core.$first]() {
+      get first() {
         if (this[_count] == 0)
           throw _internal.IterableElementError.noElement();
         return dart.as(this[_first].key, E);
       }
-      get [core.$last]() {
+      get last() {
         if (this[_count] == 0)
           throw _internal.IterableElementError.noElement();
         return dart.as(this[_last].key, E);
       }
-      get [core.$single]() {
+      get single() {
         if (this[_count] == 0)
           throw _internal.IterableElementError.noElement();
         if (dart.notNull(this[_count]) > 1)
           throw _internal.IterableElementError.tooMany();
         return this[_root].key;
       }
-      [core.$contains](object) {
+      contains(object) {
         return dart.notNull(this[_validKey](object)) && this[_splay](dart.as(object, E)) == 0;
       }
       add(element) {
         dart.as(element, E);
         let compare = this[_splay](element);
         if (compare == 0)
           return false;
         this[_addNewRoot](new (_SplayTreeNode$(E))(element), compare);
         return true;
       }
@@ skipping 37 matching lines @@
         if (!dart.notNull(this[_validKey](object)))
           return null;
         let comp = this[_splay](dart.as(object, E));
         if (comp != 0)
           return null;
         return this[_root].key;
       }
       intersection(other) {
         let result = new (SplayTreeSet$(E))(this[_comparator], this[_validKey]);
         for (let element of this) {
-          if (other[core.$contains](element))
+          if (other.contains(element))
             result.add(element);
         }
         return result;
       }
       difference(other) {
         let result = new (SplayTreeSet$(E))(this[_comparator], this[_validKey]);
         for (let element of this) {
-          if (!dart.notNull(other[core.$contains](element)))
+          if (!dart.notNull(other.contains(element)))
             result.add(element);
         }
         return result;
       }
       union(other) {
         dart.as(other, core.Set$(E));
         let _ = this[_clone]();
         _.addAll(other);
         return _;
       }
       [_clone]() {
         let set = new (SplayTreeSet$(E))(this[_comparator], this[_validKey]);
         set[_count] = this[_count];
         set[_root] = this[_copyNode](this[_root]);
         return set;
       }
       [_copyNode](node) {
         dart.as(node, _SplayTreeNode$(E));
         if (node == null)
           return null;
         let _ = new (_SplayTreeNode$(E))(node.key);
         _.left = this[_copyNode](node.left);
         _.right = this[_copyNode](node.right);
         return _;
       }
       clear() {
         this[_clear]();
       }
-      [core.$toSet]() {
+      toSet() {
         return this[_clone]();
       }
       toString() {
         return IterableBase.iterableToFullString(this, '{', '}');
       }
     }
     dart.setSignature(SplayTreeSet, {
       constructors: () => ({
         SplayTreeSet: [SplayTreeSet$(E), [], [dart.functionType(core.int, [E, E]), dart.functionType(core.bool, [core.Object])]],
         from: [SplayTreeSet$(E), [core.Iterable], [dart.functionType(core.int, [E, E]), dart.functionType(core.bool, [core.Object])]]
       }),
       methods: () => ({
         [_compare]: [core.int, [E, E]],
-        [core.$contains]: [core.bool, [core.Object]],
+        contains: [core.bool, [core.Object]],
         add: [core.bool, [E]],
         remove: [core.bool, [core.Object]],
         addAll: [dart.void, [core.Iterable$(E)]],
         lookup: [E, [core.Object]],
         intersection: [core.Set$(E), [core.Set$(core.Object)]],
         difference: [core.Set$(E), [core.Set$(core.Object)]],
         union: [core.Set$(E), [core.Set$(E)]],
         [_clone]: [SplayTreeSet$(E), []],
         [_copyNode]: [_SplayTreeNode$(E), [_SplayTreeNode$(E)]],
-        [core.$toSet]: [core.Set$(E), []]
+        toSet: [core.Set$(E), []]
       })
     });
     return SplayTreeSet;
   });
   let SplayTreeSet = SplayTreeSet$();
   let __CastType0$ = dart.generic(function(K) {
     let __CastType0 = dart.typedef('__CastType0', () => dart.functionType(core.int, [K, K]));
     return __CastType0;
   });
   let __CastType0 = __CastType0$();
@@ skipping 46 matching lines @@
         }
       }
       [_containsKey](key) {
         let rest = this[_rest];
         if (rest == null)
           return false;
         let bucket = this[_getBucket](rest, key);
         return dart.notNull(this[_findBucketIndex](bucket, key)) >= 0;
       }
       containsValue(value) {
-        return this[_computeKeys]()[core.$any](dart.fn((each => dart.equals(this.get(each), value)).bind(this), core.bool, [core.Object]));
+        return this[_computeKeys]()[dartx.any](dart.fn((each => dart.equals(this.get(each), value)).bind(this), core.bool, [core.Object]));
       }
       addAll(other) {
         dart.as(other, core.Map$(K, V));
         other.forEach(dart.fn(((key, value) => {
           dart.as(key, K);
           dart.as(value, V);
           this.set(key, value);
         }).bind(this), core.Object, [K, V]));
       }
       get(key) {
@@ skipping 87 matching lines @@
       }
       clear() {
         if (dart.notNull(this[_length]) > 0) {
           this[_strings] = this[_nums] = this[_rest] = this[_keys] = null;
           this[_length] = 0;
         }
       }
       forEach(action) {
         dart.as(action, dart.functionType(dart.void, [K, V]));
         let keys = this[_computeKeys]();
-        for (let i = 0, length = keys[core.$length]; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
+        for (let i = 0, length = keys.length; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let key = keys[i];
           action(dart.as(key, K), this.get(key));
           if (keys !== this[_keys]) {
             throw new core.ConcurrentModificationError(this);
           }
         }
       }
       [_computeKeys]() {
         if (this[_keys] != null)
           return this[_keys];
@@ skipping 223 matching lines @@
     });
     return _CustomHashMap;
   });
   let _CustomHashMap = _CustomHashMap$();
   let HashMapKeyIterable$ = dart.generic(function(E) {
     class HashMapKeyIterable extends IterableBase$(E) {
       HashMapKeyIterable(map) {
         this[_map] = map;
         super.IterableBase();
       }
-      get [core.$length]() {
+      get length() {
         return dart.as(dart.dload(this[_map], _length), core.int);
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return dart.equals(dart.dload(this[_map], _length), 0);
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (HashMapKeyIterator$(E))(this[_map], dart.as(dart.dsend(this[_map], _computeKeys), core.List));
       }
-      [core.$contains](element) {
+      contains(element) {
         return dart.as(dart.dsend(this[_map], 'containsKey', element), core.bool);
       }
-      [core.$forEach](f) {
+      forEach(f) {
         dart.as(f, dart.functionType(dart.void, [E]));
         let keys = dart.as(dart.dsend(this[_map], _computeKeys), core.List);
         for (let i = 0, length = keys.length; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           f(dart.as(keys[i], E));
           if (keys !== dart.dload(this[_map], _keys)) {
             throw new core.ConcurrentModificationError(this[_map]);
           }
         }
       }
     }
     HashMapKeyIterable[dart.implements] = () => [_internal.EfficientLength];
+    dart.implementExtension(HashMapKeyIterable, () => [core.Iterable]);
     dart.setSignature(HashMapKeyIterable, {
       constructors: () => ({HashMapKeyIterable: [HashMapKeyIterable$(E), [core.Object]]}),
-      methods: () => ({[core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]]})
+      methods: () => ({forEach: [dart.void, [dart.functionType(dart.void, [E])]]})
     });
     return HashMapKeyIterable;
   });
   let HashMapKeyIterable = HashMapKeyIterable$();
   let _offset = Symbol('_offset');
   let HashMapKeyIterator$ = dart.generic(function(E) {
     class HashMapKeyIterator extends core.Object {
       HashMapKeyIterator(map, keys) {
         this[_map] = map;
         this[_keys] = keys;
@@ skipping 76 matching lines @@
         }
       }
       [_containsKey](key) {
         let rest = this[_rest];
         if (rest == null)
           return false;
         let bucket = this[_getBucket](rest, key);
         return dart.notNull(this[_findBucketIndex](bucket, key)) >= 0;
       }
       containsValue(value) {
-        return this.keys[core.$any](dart.fn((each => dart.equals(this.get(each), value)).bind(this), core.bool, [core.Object]));
+        return this.keys[dartx.any](dart.fn((each => dart.equals(this.get(each), value)).bind(this), core.bool, [core.Object]));
       }
       addAll(other) {
         dart.as(other, core.Map$(K, V));
         other.forEach(dart.fn(((key, value) => {
           dart.as(key, K);
           dart.as(value, V);
           this.set(key, value);
         }).bind(this), core.Object, [K, V]));
       }
       get(key) {
@@ skipping 339 matching lines @@
   }
   dart.setSignature(LinkedHashMapCell, {
     constructors: () => ({LinkedHashMapCell: [LinkedHashMapCell, [core.Object, core.Object]]})
   });
   let LinkedHashMapKeyIterable$ = dart.generic(function(E) {
     class LinkedHashMapKeyIterable extends IterableBase$(E) {
       LinkedHashMapKeyIterable(map) {
         this[_map] = map;
         super.IterableBase();
       }
-      get [core.$length]() {
+      get length() {
         return dart.as(dart.dload(this[_map], _length), core.int);
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return dart.equals(dart.dload(this[_map], _length), 0);
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (LinkedHashMapKeyIterator$(E))(this[_map], dart.as(dart.dload(this[_map], _modifications), core.int));
       }
-      [core.$contains](element) {
+      contains(element) {
         return dart.as(dart.dsend(this[_map], 'containsKey', element), core.bool);
       }
-      [core.$forEach](f) {
+      forEach(f) {
         dart.as(f, dart.functionType(dart.void, [E]));
         let cell = dart.as(dart.dload(this[_map], _first), LinkedHashMapCell);
         let modifications = dart.as(dart.dload(this[_map], _modifications), core.int);
         while (cell != null) {
           f(dart.as(cell[_key], E));
           if (!dart.equals(modifications, dart.dload(this[_map], _modifications))) {
             throw new core.ConcurrentModificationError(this[_map]);
           }
           cell = cell[_next];
         }
       }
     }
     LinkedHashMapKeyIterable[dart.implements] = () => [_internal.EfficientLength];
+    dart.implementExtension(LinkedHashMapKeyIterable, () => [core.Iterable]);
     dart.setSignature(LinkedHashMapKeyIterable, {
       constructors: () => ({LinkedHashMapKeyIterable: [LinkedHashMapKeyIterable$(E), [core.Object]]}),
-      methods: () => ({[core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]]})
+      methods: () => ({forEach: [dart.void, [dart.functionType(dart.void, [E])]]})
     });
     return LinkedHashMapKeyIterable;
   });
   let LinkedHashMapKeyIterable = LinkedHashMapKeyIterable$();
   let _cell = Symbol('_cell');
   let LinkedHashMapKeyIterator$ = dart.generic(function(E) {
     class LinkedHashMapKeyIterator extends core.Object {
       LinkedHashMapKeyIterator(map, modifications) {
         this[_map] = map;
         this[_modifications] = modifications;
@@ skipping 34 matching lines @@
       _HashSet() {
         this[_length] = 0;
         this[_strings] = null;
         this[_nums] = null;
         this[_rest] = null;
         this[_elements] = null;
       }
       [_newSet]() {
         return new (_HashSet$(E))();
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (HashSetIterator$(E))(this, this[_computeElements]());
       }
-      get [core.$length]() {
+      get length() {
         return this[_length];
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return this[_length] == 0;
       }
-      get [core.$isNotEmpty]() {
-        return !dart.notNull(this[core.$isEmpty]);
+      get isNotEmpty() {
+        return !dart.notNull(this.isEmpty);
       }
-      [core.$contains](object) {
+      contains(object) {
         if (_HashSet$()._isStringElement(object)) {
           let strings = this[_strings];
           return strings == null ? false : _HashSet$()._hasTableEntry(strings, object);
         } else if (_HashSet$()._isNumericElement(object)) {
           let nums = this[_nums];
           return nums == null ? false : _HashSet$()._hasTableEntry(nums, object);
         } else {
           return this[_contains](object);
         }
       }
       [_contains](object) {
         let rest = this[_rest];
         if (rest == null)
           return false;
         let bucket = this[_getBucket](rest, object);
         return dart.notNull(this[_findBucketIndex](bucket, object)) >= 0;
       }
       lookup(object) {
         if (dart.notNull(_HashSet$()._isStringElement(object)) || dart.notNull(_HashSet$()._isNumericElement(object))) {
-          return dart.as(this[core.$contains](object) ? object : null, E);
+          return dart.as(this.contains(object) ? object : null, E);
         }
         return this[_lookup](object);
       }
       [_lookup](object) {
         let rest = this[_rest];
         if (rest == null)
           return null;
         let bucket = this[_getBucket](rest, object);
         let index = this[_findBucketIndex](bucket, object);
         if (dart.notNull(index) < 0)
           return null;
-        return dart.as(bucket[core.$get](index), E);
+        return dart.as(bucket[dartx.get](index), E);
       }
       add(element) {
         dart.as(element, E);
         if (_HashSet$()._isStringElement(element)) {
           let strings = this[_strings];
           if (strings == null)
             this[_strings] = strings = _HashSet$()._newHashTable();
           return this[_addHashTableEntry](strings, element);
         } else if (_HashSet$()._isNumericElement(element)) {
           let nums = this[_nums];
@@ skipping 154 matching lines @@
       }
       static _newHashTable() {
         let table = Object.create(null);
         let temporaryKey = '<non-identifier-key>';
         _HashSet$()._setTableEntry(table, temporaryKey, table);
         _HashSet$()._deleteTableEntry(table, temporaryKey);
         return table;
       }
     }
     _HashSet[dart.implements] = () => [HashSet$(E)];
+    dart.implementExtension(_HashSet, () => [core.Iterable]);
     dart.setSignature(_HashSet, {
       constructors: () => ({_HashSet: [_HashSet$(E), []]}),
       methods: () => ({
         [_newSet]: [core.Set$(E), []],
-        [core.$contains]: [core.bool, [core.Object]],
+        contains: [core.bool, [core.Object]],
         [_contains]: [core.bool, [core.Object]],
         lookup: [E, [core.Object]],
         [_lookup]: [E, [core.Object]],
         add: [core.bool, [E]],
         [_add]: [core.bool, [E]],
         addAll: [dart.void, [core.Iterable$(E)]],
         remove: [core.bool, [core.Object]],
         [_remove]: [core.bool, [core.Object]],
         [_computeElements]: [core.List, []],
         [_addHashTableEntry]: [core.bool, [core.Object, E]],
@@ skipping 66 matching lines @@
         }
         return -1;
       }
       [_computeHashCode](element) {
         return this[_hasher](dart.as(element, E)) & 0x3ffffff;
       }
       add(object) {
         dart.as(object, E);
         return super[_add](object);
       }
-      [core.$contains](object) {
+      contains(object) {
         if (!dart.notNull(this[_validKey](object)))
           return false;
         return super[_contains](object);
       }
       lookup(object) {
         if (!dart.notNull(this[_validKey](object)))
           return null;
         return super[_lookup](object);
       }
       remove(object) {
@@ skipping 58 matching lines @@
         this[_first] = null;
         this[_last] = null;
         this[_modifications] = 0;
       }
       [_newSet]() {
         return new (_LinkedHashSet$(E))();
       }
       [_unsupported](operation) {
         throw `LinkedHashSet: unsupported ${operation}`;
       }
-      get [core.$iterator]() {
+      get iterator() {
         return new (LinkedHashSetIterator$(E))(this, this[_modifications]);
       }
-      get [core.$length]() {
+      get length() {
         return this[_length];
       }
-      get [core.$isEmpty]() {
+      get isEmpty() {
         return this[_length] == 0;
       }
-      get [core.$isNotEmpty]() {
-        return !dart.notNull(this[core.$isEmpty]);
+      get isNotEmpty() {
+        return !dart.notNull(this.isEmpty);
       }
-      [core.$contains](object) {
+      contains(object) {
         if (_LinkedHashSet$()._isStringElement(object)) {
           let strings = this[_strings];
           if (strings == null)
             return false;
           let cell = dart.as(_LinkedHashSet$()._getTableEntry(strings, object), LinkedHashSetCell);
           return cell != null;
         } else if (_LinkedHashSet$()._isNumericElement(object)) {
           let nums = this[_nums];
           if (nums == null)
             return false;
           let cell = dart.as(_LinkedHashSet$()._getTableEntry(nums, object), LinkedHashSetCell);
           return cell != null;
         } else {
           return this[_contains](object);
         }
       }
       [_contains](object) {
         let rest = this[_rest];
         if (rest == null)
           return false;
         let bucket = this[_getBucket](rest, object);
         return dart.notNull(this[_findBucketIndex](bucket, object)) >= 0;
       }
       lookup(object) {
         if (dart.notNull(_LinkedHashSet$()._isStringElement(object)) || dart.notNull(_LinkedHashSet$()._isNumericElement(object))) {
-          return dart.as(this[core.$contains](object) ? object : null, E);
+          return dart.as(this.contains(object) ? object : null, E);
         } else {
           return this[_lookup](object);
         }
       }
       [_lookup](object) {
         let rest = this[_rest];
         if (rest == null)
           return null;
         let bucket = this[_getBucket](rest, object);
         let index = this[_findBucketIndex](bucket, object);
         if (dart.notNull(index) < 0)
           return null;
-        return dart.as(dart.dload(bucket[core.$get](index), _element), E);
+        return dart.as(dart.dload(bucket[dartx.get](index), _element), E);
       }
-      [core.$forEach](action) {
+      forEach(action) {
         dart.as(action, dart.functionType(dart.void, [E]));
         let cell = this[_first];
         let modifications = this[_modifications];
         while (cell != null) {
           action(dart.as(cell[_element], E));
           if (modifications != this[_modifications]) {
             throw new core.ConcurrentModificationError(this);
           }
           cell = cell[_next];
         }
       }
-      get [core.$first]() {
+      get first() {
         if (this[_first] == null)
           throw new core.StateError("No elements");
         return dart.as(this[_first][_element], E);
       }
-      get [core.$last]() {
+      get last() {
         if (this[_last] == null)
           throw new core.StateError("No elements");
         return dart.as(this[_last][_element], E);
       }
       add(element) {
         dart.as(element, E);
         if (_LinkedHashSet$()._isStringElement(element)) {
           let strings = this[_strings];
           if (strings == null)
             this[_strings] = strings = _LinkedHashSet$()._newHashTable();
@@ skipping 167 matching lines @@
       }
       static _newHashTable() {
         let table = Object.create(null);
         let temporaryKey = '<non-identifier-key>';
         _LinkedHashSet$()._setTableEntry(table, temporaryKey, table);
         _LinkedHashSet$()._deleteTableEntry(table, temporaryKey);
         return table;
       }
     }
     _LinkedHashSet[dart.implements] = () => [LinkedHashSet$(E)];
+    dart.implementExtension(_LinkedHashSet, () => [core.Iterable]);
     dart.setSignature(_LinkedHashSet, {
       constructors: () => ({_LinkedHashSet: [_LinkedHashSet$(E), []]}),
       methods: () => ({
         [_newSet]: [core.Set$(E), []],
         [_unsupported]: [dart.void, [core.String]],
-        [core.$contains]: [core.bool, [core.Object]],
+        contains: [core.bool, [core.Object]],
         [_contains]: [core.bool, [core.Object]],
         lookup: [E, [core.Object]],
         [_lookup]: [E, [core.Object]],
-        [core.$forEach]: [dart.void, [dart.functionType(dart.void, [E])]],
+        forEach: [dart.void, [dart.functionType(dart.void, [E])]],
         add: [core.bool, [E]],
         [_add]: [core.bool, [E]],
         remove: [core.bool, [core.Object]],
         [_remove]: [core.bool, [core.Object]],
         removeWhere: [dart.void, [dart.functionType(core.bool, [E])]],
         retainWhere: [dart.void, [dart.functionType(core.bool, [E])]],
         [_filterWhere]: [dart.void, [dart.functionType(core.bool, [E]), core.bool]],
         [_addHashTableEntry]: [core.bool, [core.Object, E]],
         [_removeHashTableEntry]: [core.bool, [core.Object, core.Object]],
         [_modified]: [dart.void, []],
@@ skipping 67 matching lines @@
         }
         return -1;
       }
       [_computeHashCode](element) {
         return this[_hasher](dart.as(element, E)) & 0x3ffffff;
       }
       add(element) {
         dart.as(element, E);
         return super[_add](element);
       }
-      [core.$contains](object) {
+      contains(object) {
         if (!dart.notNull(this[_validKey](object)))
           return false;
         return super[_contains](object);
       }
       lookup(object) {
         if (!dart.notNull(this[_validKey](object)))
           return null;
         return super[_lookup](object);
       }
       remove(object) {
         if (!dart.notNull(this[_validKey](object)))
           return false;
         return super[_remove](object);
       }
       containsAll(elements) {
         for (let element of elements) {
-          if (!dart.notNull(this[_validKey](element)) || !dart.notNull(this[core.$contains](element)))
+          if (!dart.notNull(this[_validKey](element)) || !dart.notNull(this.contains(element)))
             return false;
         }
         return true;
       }
       removeAll(elements) {
         for (let element of elements) {
           if (this[_validKey](element)) {
             super[_remove](element);
           }
         }
@@ skipping 112 matching lines @@
   exports.LinkedHashMapKeyIterable$ = LinkedHashMapKeyIterable$;
   exports.LinkedHashMapKeyIterable = LinkedHashMapKeyIterable;
   exports.LinkedHashMapKeyIterator$ = LinkedHashMapKeyIterator$;
   exports.LinkedHashMapKeyIterator = LinkedHashMapKeyIterator;
   exports.HashSetIterator$ = HashSetIterator$;
   exports.HashSetIterator = HashSetIterator;
   exports.LinkedHashSetCell = LinkedHashSetCell;
   exports.LinkedHashSetIterator$ = LinkedHashSetIterator$;
   exports.LinkedHashSetIterator = LinkedHashSetIterator;
 })(collection, _internal, core, _js_helper, math);