use == and != to enable handling null/undefined

lib/runtime/dart/collection.js

 var collection;
 (function(exports) {
   'use strict';
   let _source = Symbol('_source');
   let UnmodifiableListView$ = dart.generic(function(E) {
     class UnmodifiableListView extends _internal.UnmodifiableListBase$(E) {
       UnmodifiableListView(source) {
         this[_source] = source;
         super.UnmodifiableListBase();
       }
@@ skipping 14 matching lines @@
   // Function _defaultHashCode: (dynamic) → int
   function _defaultHashCode(a) {
     return dart.as(dart.dload(a, 'hashCode'), core.int);
   }
   let HashMap$ = dart.generic(function(K, V) {
     class HashMap extends core.Object {
       HashMap(opts) {
         let equals = opts && 'equals' in opts ? opts.equals : null;
         let hashCode = opts && 'hashCode' in opts ? opts.hashCode : null;
         let isValidKey = opts && 'isValidKey' in opts ? opts.isValidKey : null;
-        if (isValidKey === null) {
-          if (hashCode === null) {
-            if (equals === null) {
+        if (isValidKey == null) {
+          if (hashCode == null) {
+            if (equals == null) {
               return new _HashMap();
             }
             hashCode = dart.closureWrap(_defaultHashCode, "(K) → int");
           } else {
             if (dart.notNull(core.identical(core.identityHashCode, hashCode)) && dart.notNull(core.identical(core.identical, equals))) {
               return new _IdentityHashMap();
             }
-            if (equals === null) {
+            if (equals == null) {
               equals = dart.closureWrap(_defaultEquals, "(K, K) → bool");
             }
           }
         } else {
-          if (hashCode === null) {
+          if (hashCode == null) {
             hashCode = dart.closureWrap(_defaultHashCode, "(K) → int");
           }
-          if (equals === null) {
+          if (equals == null) {
             equals = dart.closureWrap(_defaultEquals, "(K, K) → bool");
           }
         }
         return new _CustomHashMap(equals, hashCode, isValidKey);
       }
       identity() {
         return new _IdentityHashMap();
       }
       from(other) {
         let result = new HashMap();
@@ skipping 19 matching lines @@
     dart.defineNamedConstructor(HashMap, 'from');
     dart.defineNamedConstructor(HashMap, 'fromIterable');
     dart.defineNamedConstructor(HashMap, 'fromIterables');
     return HashMap;
   });
   let HashMap = HashMap$(dart.dynamic, dart.dynamic);
   let _newSet = Symbol('_newSet');
   let SetMixin$ = dart.generic(function(E) {
     class SetMixin extends core.Object {
       get isEmpty() {
-        return this.length === 0;
+        return this.length == 0;
       }
       get isNotEmpty() {
-        return this.length !== 0;
+        return this.length != 0;
       }
       clear() {
         this.removeAll(this.toList());
       }
       addAll(elements) {
         for (let element of elements)
           this.add(element);
       }
       removeAll(elements) {
         for (let element of elements)
@@ skipping 111 matching lines @@
         }
         return true;
       }
       join(separator) {
         if (separator === void 0)
           separator = "";
         let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext()))
           return "";
         let buffer = new core.StringBuffer();
-        if (dart.notNull(separator === null) || dart.notNull(dart.equals(separator, ""))) {
+        if (dart.notNull(separator == null) || dart.notNull(separator == "")) {
           do {
             buffer.write(`${iterator.current}`);
           } while (iterator.moveNext());
         } else {
           buffer.write(`${iterator.current}`);
           while (iterator.moveNext()) {
             buffer.write(separator);
             buffer.write(`${iterator.current}`);
           }
         }
@@ skipping 35 matching lines @@
           result = dart.as(it.current, E);
         } while (it.moveNext());
         return result;
       }
       firstWhere(test, opts) {
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         for (let element of this) {
           if (test(element))
             return element;
         }
-        if (orElse !== null)
+        if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
       lastWhere(test, opts) {
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         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)
+        if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
       singleWhere(test) {
         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();
       }
       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)
+          if (index == elementIndex)
             return element;
           elementIndex = dart.notNull(elementIndex) + 1;
         }
         throw new core.RangeError.index(index, this, "index", null, elementIndex);
       }
     }
     return SetMixin;
   });
   let SetMixin = SetMixin$(dart.dynamic);
   let SetBase$ = dart.generic(function(E) {
@@ skipping 32 matching lines @@
     }
     return _HashSetBase;
   });
   let _HashSetBase = _HashSetBase$(dart.dynamic);
   let HashSet$ = dart.generic(function(E) {
     class HashSet extends core.Object {
       HashSet(opts) {
         let equals = opts && 'equals' in opts ? opts.equals : null;
         let hashCode = opts && 'hashCode' in opts ? opts.hashCode : null;
         let isValidKey = opts && 'isValidKey' in opts ? opts.isValidKey : null;
-        if (isValidKey === null) {
-          if (hashCode === null) {
-            if (equals === null) {
+        if (isValidKey == null) {
+          if (hashCode == null) {
+            if (equals == null) {
               return new _HashSet();
             }
             hashCode = dart.closureWrap(_defaultHashCode, "(E) → int");
           } else {
             if (dart.notNull(core.identical(core.identityHashCode, hashCode)) && dart.notNull(core.identical(core.identical, equals))) {
               return new _IdentityHashSet();
             }
-            if (equals === null) {
+            if (equals == null) {
               equals = dart.closureWrap(_defaultEquals, "(E, E) → bool");
             }
           }
         } else {
-          if (hashCode === null) {
+          if (hashCode == null) {
             hashCode = dart.closureWrap(_defaultHashCode, "(E) → int");
           }
-          if (equals === null) {
+          if (equals == null) {
             equals = dart.closureWrap(_defaultEquals, "(E, E) → bool");
           }
         }
         return new _CustomHashSet(equals, hashCode, isValidKey);
       }
       identity() {
         return new _IdentityHashSet();
       }
       from(elements) {
         let result = new HashSet();
@@ skipping 53 matching lines @@
         }
         return true;
       }
       join(separator) {
         if (separator === void 0)
           separator = "";
         let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext()))
           return "";
         let buffer = new core.StringBuffer();
-        if (dart.notNull(separator === null) || dart.notNull(dart.equals(separator, ""))) {
+        if (dart.notNull(separator == null) || dart.notNull(separator == "")) {
           do {
             buffer.write(`${iterator.current}`);
           } while (iterator.moveNext());
         } else {
           buffer.write(`${iterator.current}`);
           while (iterator.moveNext()) {
             buffer.write(separator);
             buffer.write(`${iterator.current}`);
           }
         }
@@ skipping 66 matching lines @@
         if (it.moveNext())
           throw _internal.IterableElementError.tooMany();
         return result;
       }
       firstWhere(test, opts) {
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         for (let element of this) {
           if (test(element))
             return element;
         }
-        if (orElse !== null)
+        if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
       lastWhere(test, opts) {
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         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)
+        if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
       singleWhere(test) {
         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();
       }
       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)
+          if (index == elementIndex)
             return element;
           elementIndex = dart.notNull(elementIndex) + 1;
         }
         throw new core.RangeError.index(index, this, "index", null, elementIndex);
       }
       toString() {
         return IterableBase.iterableToShortString(this, '(', ')');
       }
     }
     return IterableMixin;
@@ skipping 50 matching lines @@
         }
         return true;
       }
       join(separator) {
         if (separator === void 0)
           separator = "";
         let iterator = this.iterator;
         if (!dart.notNull(iterator.moveNext()))
           return "";
         let buffer = new core.StringBuffer();
-        if (dart.notNull(separator === null) || dart.notNull(dart.equals(separator, ""))) {
+        if (dart.notNull(separator == null) || dart.notNull(separator == "")) {
           do {
             buffer.write(`${iterator.current}`);
           } while (iterator.moveNext());
         } else {
           buffer.write(`${iterator.current}`);
           while (iterator.moveNext()) {
             buffer.write(separator);
             buffer.write(`${iterator.current}`);
           }
         }
@@ skipping 66 matching lines @@
         if (it.moveNext())
           throw _internal.IterableElementError.tooMany();
         return result;
       }
       firstWhere(test, opts) {
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         for (let element of this) {
           if (test(element))
             return element;
         }
-        if (orElse !== null)
+        if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
       lastWhere(test, opts) {
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         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)
+        if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
       singleWhere(test) {
         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();
       }
       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)
+          if (index == elementIndex)
             return element;
           elementIndex = dart.notNull(elementIndex) + 1;
         }
         throw new 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 (dart.notNull(dart.equals(leftDelimiter, "(")) && dart.notNull(dart.equals(rightDelimiter, ")"))) {
+          if (dart.notNull(leftDelimiter == "(") && dart.notNull(rightDelimiter == ")")) {
             return "(...)";
           }
           return `${leftDelimiter}...${rightDelimiter}`;
         }
         let parts = new core.List.from([]);
         IterableBase[_toStringVisiting].add(iterable);
         try {
           IterableBase[_iterablePartsToStrings](iterable, parts);
         } finally {
           dart.assert(core.identical(IterableBase[_toStringVisiting].last, iterable));
@@ skipping 91 matching lines @@
             length = dart.notNull(ultimateString.length) + dart.notNull(penultimateString.length) + 2 * dart.notNull(OVERHEAD);
           }
         }
         let elision = null;
         if (dart.notNull(count) > dart.notNull(parts.length) + dart.notNull(TAIL_COUNT)) {
           elision = "...";
           length = dart.notNull(ELLIPSIS_SIZE) + dart.notNull(OVERHEAD);
         }
         while (dart.notNull(length) > dart.notNull(LENGTH_LIMIT) && dart.notNull(parts.length) > dart.notNull(HEAD_COUNT)) {
           length = dart.as(dart.dbinary(dart.dload(parts.removeLast(), 'length'), '+', OVERHEAD), core.int);
-          if (elision === null) {
+          if (elision == null) {
             elision = "...";
             length = dart.notNull(ELLIPSIS_SIZE) + dart.notNull(OVERHEAD);
           }
         }
-        if (elision !== null) {
+        if (elision != null) {
           parts.add(elision);
         }
         parts.add(penultimateString);
         parts.add(ultimateString);
       }
     }
     dart.defineLazyProperties(IterableBase, {
       get _toStringVisiting() {
         return new core.List.from([]);
       }
     });
     return IterableBase;
   });
   let IterableBase = IterableBase$(dart.dynamic);
   let _iterator = Symbol('_iterator');
   let _NOT_MOVED_YET = Symbol('_NOT_MOVED_YET');
   let _state = Symbol('_state');
   let _move = Symbol('_move');
   let _HAS_NEXT_AND_NEXT_IN_CURRENT = Symbol('_HAS_NEXT_AND_NEXT_IN_CURRENT');
   let _NO_NEXT = Symbol('_NO_NEXT');
   let HasNextIterator$ = dart.generic(function(E) {
     class HasNextIterator extends core.Object {
       HasNextIterator(iterator$) {
         this[_iterator] = iterator$;
         this[_state] = HasNextIterator[_NOT_MOVED_YET];
       }
       get hasNext() {
-        if (this[_state] === HasNextIterator[_NOT_MOVED_YET])
+        if (this[_state] == HasNextIterator[_NOT_MOVED_YET])
           this[_move]();
-        return this[_state] === HasNextIterator[_HAS_NEXT_AND_NEXT_IN_CURRENT];
+        return this[_state] == HasNextIterator[_HAS_NEXT_AND_NEXT_IN_CURRENT];
       }
       next() {
         if (!dart.notNull(this.hasNext))
           throw new core.StateError("No more elements");
-        dart.assert(this[_state] === HasNextIterator[_HAS_NEXT_AND_NEXT_IN_CURRENT]);
+        dart.assert(this[_state] == HasNextIterator[_HAS_NEXT_AND_NEXT_IN_CURRENT]);
         let result = dart.as(this[_iterator].current, E);
         this[_move]();
         return result;
       }
       [_move]() {
         if (this[_iterator].moveNext()) {
           this[_state] = HasNextIterator[_HAS_NEXT_AND_NEXT_IN_CURRENT];
         } else {
           this[_state] = HasNextIterator[_NO_NEXT];
         }
       }
     }
     HasNextIterator._HAS_NEXT_AND_NEXT_IN_CURRENT = 0;
     HasNextIterator._NO_NEXT = 1;
     HasNextIterator._NOT_MOVED_YET = 2;
     return HasNextIterator;
   });
   let HasNextIterator = HasNextIterator$(dart.dynamic);
   let _literal = Symbol('_literal');
   let _empty = Symbol('_empty');
   let LinkedHashMap$ = dart.generic(function(K, V) {
     class LinkedHashMap extends core.Object {
       LinkedHashMap(opts) {
         let equals = opts && 'equals' in opts ? opts.equals : null;
         let hashCode = opts && 'hashCode' in opts ? opts.hashCode : null;
         let isValidKey = opts && 'isValidKey' in opts ? opts.isValidKey : null;
-        if (isValidKey === null) {
-          if (hashCode === null) {
-            if (equals === null) {
+        if (isValidKey == null) {
+          if (hashCode == null) {
+            if (equals == null) {
               return new _LinkedHashMap();
             }
             hashCode = dart.closureWrap(_defaultHashCode, "(K) → int");
           } else {
             if (dart.notNull(core.identical(core.identityHashCode, hashCode)) && dart.notNull(core.identical(core.identical, equals))) {
               return new _LinkedIdentityHashMap();
             }
-            if (equals === null) {
+            if (equals == null) {
               equals = dart.closureWrap(_defaultEquals, "(K, K) → bool");
             }
           }
         } else {
-          if (hashCode === null) {
+          if (hashCode == null) {
             hashCode = dart.closureWrap(_defaultHashCode, "(K) → int");
           }
-          if (equals === null) {
+          if (equals == null) {
             equals = dart.closureWrap(_defaultEquals, "(K, K) → bool");
           }
         }
         return new _LinkedCustomHashMap(equals, hashCode, isValidKey);
       }
       identity() {
         return new _LinkedIdentityHashMap();
       }
       from(other) {
         let result = new LinkedHashMap();
@@ skipping 29 matching lines @@
     dart.defineNamedConstructor(LinkedHashMap, _empty);
     return LinkedHashMap;
   });
   let LinkedHashMap = LinkedHashMap$(dart.dynamic, dart.dynamic);
   let LinkedHashSet$ = dart.generic(function(E) {
     class LinkedHashSet extends core.Object {
       LinkedHashSet(opts) {
         let equals = opts && 'equals' in opts ? opts.equals : null;
         let hashCode = opts && 'hashCode' in opts ? opts.hashCode : null;
         let isValidKey = opts && 'isValidKey' in opts ? opts.isValidKey : null;
-        if (isValidKey === null) {
-          if (hashCode === null) {
-            if (equals === null) {
+        if (isValidKey == null) {
+          if (hashCode == null) {
+            if (equals == null) {
               return new _LinkedHashSet();
             }
             hashCode = dart.closureWrap(_defaultHashCode, "(E) → int");
           } else {
             if (dart.notNull(core.identical(core.identityHashCode, hashCode)) && dart.notNull(core.identical(core.identical, equals))) {
               return new _LinkedIdentityHashSet();
             }
-            if (equals === null) {
+            if (equals == null) {
               equals = dart.closureWrap(_defaultEquals, "(E, E) → bool");
             }
           }
         } else {
-          if (hashCode === null) {
+          if (hashCode == null) {
             hashCode = dart.closureWrap(_defaultHashCode, "(E) → int");
           }
-          if (equals === null) {
+          if (equals == null) {
             equals = dart.closureWrap(_defaultEquals, "(E, E) → bool");
           }
         }
         return new _LinkedCustomHashSet(equals, hashCode, isValidKey);
       }
       identity() {
         return new _LinkedIdentityHashSet();
       }
       from(elements) {
         let result = new LinkedHashSet();
@@ skipping 76 matching lines @@
         if (!dart.notNull(core.identical(this[_previous], this[_next]))) {
           throw new core.StateError('Too many elements');
         }
         return dart.as(this[_next], E);
       }
       forEach(action) {
         let modificationCount = this[_modificationCount];
         let current = this[_next];
         while (!dart.notNull(core.identical(current, this))) {
           action(dart.as(current, E));
-          if (modificationCount !== this[_modificationCount]) {
+          if (modificationCount != this[_modificationCount]) {
             throw new core.ConcurrentModificationError(this);
           }
           current = current[_next];
         }
       }
       get isEmpty() {
-        return this[_length] === 0;
+        return this[_length] == 0;
       }
       [_insertAfter](entry, newEntry) {
-        if (newEntry.list !== null) {
+        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;
@@ skipping 20 matching lines @@
         this[_current] = null;
       }
       get current() {
         return this[_current];
       }
       moveNext() {
         if (core.identical(this[_next], this[_list])) {
           this[_current] = null;
           return false;
         }
-        if (this[_modificationCount] !== this[_list][_modificationCount]) {
+        if (this[_modificationCount] != this[_list][_modificationCount]) {
           throw new core.ConcurrentModificationError(this);
         }
         this[_current] = dart.as(this[_next], E);
         this[_next] = this[_next][_next];
         return true;
       }
     }
     return _LinkedListIterator;
   });
   let _LinkedListIterator = _LinkedListIterator$(dart.dynamic);
@@ skipping 43 matching lines @@
       get iterator() {
         return new _internal.ListIterator(this);
       }
       elementAt(index) {
         return this.get(index);
       }
       forEach(action) {
         let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           action(this.get(i));
-          if (length !== this.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
       }
       get isEmpty() {
-        return this.length === 0;
+        return this.length == 0;
       }
       get isNotEmpty() {
         return !dart.notNull(this.isEmpty);
       }
       get first() {
-        if (this.length === 0)
+        if (this.length == 0)
           throw _internal.IterableElementError.noElement();
         return this.get(0);
       }
       get last() {
-        if (this.length === 0)
+        if (this.length == 0)
           throw _internal.IterableElementError.noElement();
         return this.get(dart.notNull(this.length) - 1);
       }
       get single() {
-        if (this.length === 0)
+        if (this.length == 0)
           throw _internal.IterableElementError.noElement();
         if (dart.notNull(this.length) > 1)
           throw _internal.IterableElementError.tooMany();
         return this.get(0);
       }
       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.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return false;
       }
       every(test) {
         let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           if (!dart.notNull(test(this.get(i))))
             return false;
-          if (length !== this.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return true;
       }
       any(test) {
         let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           if (test(this.get(i)))
             return true;
-          if (length !== this.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return false;
       }
       firstWhere(test, opts) {
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let element = this.get(i);
           if (test(element))
             return element;
-          if (length !== this.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
-        if (orElse !== null)
+        if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
       lastWhere(test, opts) {
         let orElse = opts && 'orElse' in opts ? opts.orElse : null;
         let length = this.length;
         for (let i = dart.notNull(length) - 1; dart.notNull(i) >= 0; i = dart.notNull(i) - 1) {
           let element = this.get(i);
           if (test(element))
             return element;
-          if (length !== this.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
-        if (orElse !== null)
+        if (orElse != null)
           return orElse();
         throw _internal.IterableElementError.noElement();
       }
       singleWhere(test) {
         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.get(i);
           if (test(element)) {
             if (matchFound) {
               throw _internal.IterableElementError.tooMany();
             }
             matchFound = true;
             match = element;
           }
-          if (length !== this.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         if (matchFound)
           return match;
         throw _internal.IterableElementError.noElement();
       }
       join(separator) {
         if (separator === void 0)
           separator = "";
-        if (this.length === 0)
+        if (this.length == 0)
           return "";
         let buffer = new core.StringBuffer();
         buffer.writeAll(this, separator);
         return buffer.toString();
       }
       where(test) {
         return new _internal.WhereIterable(this, test);
       }
       map(f) {
         return new _internal.MappedListIterable(this, f);
       }
       expand(f) {
         return new _internal.ExpandIterable(this, f);
       }
       reduce(combine) {
         let length = this.length;
-        if (length === 0)
+        if (length == 0)
           throw _internal.IterableElementError.noElement();
         let value = this.get(0);
         for (let i = 1; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           value = combine(value, this.get(i));
-          if (length !== this.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return value;
       }
       fold(initialValue, combine) {
         let value = initialValue;
         let length = this.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           value = dart.dinvokef(combine, value, this.get(i));
-          if (length !== this.length) {
+          if (length != this.length) {
             throw new core.ConcurrentModificationError(this);
           }
         }
         return value;
       }
       skip(count) {
         return new _internal.SubListIterable(this, count, null);
       }
       skipWhile(test) {
         return new _internal.SkipWhileIterable(this, test);
@@ skipping 49 matching lines @@
         ListMixin[_filter](this, test, false);
       }
       retainWhere(test) {
         ListMixin[_filter](this, test, true);
       }
       static [_filter](source, test, retainMatching) {
         let retained = new core.List.from([]);
         let length = source.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let element = source.get(i);
-          if (dart.dinvokef(test, element) === retainMatching) {
+          if (dart.dinvokef(test, element) == retainMatching) {
             retained.add(element);
           }
-          if (length !== source.length) {
+          if (length != source.length) {
             throw new core.ConcurrentModificationError(source);
           }
         }
-        if (retained.length !== source.length) {
+        if (retained.length != source.length) {
           source.setRange(0, retained.length, retained);
           source.length = retained.length;
         }
       }
       clear() {
         this.length = 0;
       }
       removeLast() {
-        if (this.length === 0) {
+        if (this.length == 0) {
           throw _internal.IterableElementError.noElement();
         }
         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;
-        if (compare === null) {
+        if (compare == null) {
           let defaultCompare = core.Comparable.compare;
           compare = defaultCompare;
         }
         _internal.Sort.sort(this, compare);
       }
       shuffle(random) {
         if (random === void 0)
           random = null;
-        if (random === null)
+        if (random == null)
           random = new math.Random();
         let length = this.length;
         while (dart.notNull(length) > 1) {
           let pos = random.nextInt(length);
           length = 1;
           let tmp = this.get(length);
           this.set(length, this.get(pos));
           this.set(pos, tmp);
         }
       }
       asMap() {
         return new _internal.ListMapView(this);
       }
       sublist(start, end) {
         if (end === void 0)
           end = null;
         let listLength = this.length;
-        if (end === null)
+        if (end == null)
           end = listLength;
         core.RangeError.checkValidRange(start, end, listLength);
         let length = dart.notNull(end) - dart.notNull(start);
         let result = new core.List();
         result.length = length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           result.set(i, this.get(dart.notNull(start) + dart.notNull(i)));
         }
         return result;
       }
@@ skipping 13 matching lines @@
         core.RangeError.checkValidRange(start, end, this.length);
         for (let i = start; dart.notNull(i) < dart.notNull(end); i = dart.notNull(i) + 1) {
           this.set(i, fill);
         }
       }
       setRange(start, end, iterable, skipCount) {
         if (skipCount === void 0)
           skipCount = 0;
         core.RangeError.checkValidRange(start, end, this.length);
         let length = dart.notNull(end) - dart.notNull(start);
-        if (length === 0)
+        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.skip(skipCount).toList({growable: false});
           otherStart = 0;
@@ skipping 16 matching lines @@
         if (!dart.is(newContents, _internal.EfficientLength)) {
           newContents = newContents.toList();
         }
         let removeLength = dart.notNull(end) - dart.notNull(start);
         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.length) - dart.notNull(delta);
           this.setRange(start, insertEnd, newContents);
-          if (delta !== 0) {
+          if (delta != 0) {
             this.setRange(insertEnd, newLength, this, end);
             this.length = newLength;
           }
         } else {
           let delta = dart.notNull(insertLength) - dart.notNull(removeLength);
           let newLength = dart.notNull(this.length) + dart.notNull(delta);
           let insertEnd = dart.notNull(start) + dart.notNull(insertLength);
           this.length = newLength;
           this.setRange(insertEnd, newLength, this, end);
           this.setRange(start, insertEnd, newContents);
@@ skipping 11 matching lines @@
         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;
       }
       lastIndexOf(element, startIndex) {
         if (startIndex === void 0)
           startIndex = null;
-        if (startIndex === null) {
+        if (startIndex == null) {
           startIndex = dart.notNull(this.length) - 1;
         } else {
           if (dart.notNull(startIndex) < 0) {
             return -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.get(i), element)) {
             return i;
           }
         }
         return -1;
       }
       insert(index, element) {
         core.RangeError.checkValueInInterval(index, 0, this.length, "index");
-        if (index === this.length) {
+        if (index == this.length) {
           this.add(element);
           return;
         }
         if (!(typeof index == 'number'))
           throw new core.ArgumentError(index);
         this.length = dart.notNull(this.length) + 1;
         this.setRange(dart.notNull(index) + 1, this.length, this, index);
         this.set(index, element);
       }
       removeAt(index) {
@@ skipping 307 matching lines @@
       } finally {
         dart.assert(core.identical(IterableBase[_toStringVisiting].last, m));
         IterableBase[_toStringVisiting].removeLast();
       }
       return result.toString();
     }
     static [_id](x) {
       return x;
     }
     static [_fillMapWithMappedIterable](map, iterable, key, value) {
-      if (key === null)
+      if (key == null)
         key = Maps[_id];
-      if (value === null)
+      if (value == null)
         value = Maps[_id];
       for (let element of iterable) {
         map.set(dart.dinvokef(key, element), dart.dinvokef(value, element));
       }
     }
     static [_fillMapWithIterables](map, keys, values) {
       let keyIterator = keys.iterator;
       let valueIterator = values.iterator;
       let hasNextKey = keyIterator.moveNext();
       let hasNextValue = valueIterator.moveNext();
@@ skipping 253 matching lines @@
   let ListQueue$ = dart.generic(function(E) {
     class ListQueue extends IterableBase$(E) {
       ListQueue(initialCapacity) {
         if (initialCapacity === void 0)
           initialCapacity = null;
         this[_head] = 0;
         this[_tail] = 0;
         this[_table] = null;
         this[_modificationCount] = 0;
         super.IterableBase();
-        if (initialCapacity === null || dart.notNull(initialCapacity) < dart.notNull(ListQueue[_INITIAL_CAPACITY])) {
+        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] = new core.List(initialCapacity);
       }
       from(elements) {
         if (dart.is(elements, core.List)) {
           let length = elements.length;
@@ skipping 13 matching lines @@
             result.addLast(element);
           }
           return result;
         }
       }
       get iterator() {
         return new _ListQueueIterator(this);
       }
       forEach(action) {
         let modificationCount = this[_modificationCount];
-        for (let i = this[_head]; i !== this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table].length) - 1) {
+        for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table].length) - 1) {
           action(this[_table].get(i));
           this[_checkModification](modificationCount);
         }
       }
       get isEmpty() {
-        return this[_head] === this[_tail];
+        return this[_head] == this[_tail];
       }
       get length() {
         return dart.notNull(this[_tail]) - dart.notNull(this[_head]) & dart.notNull(this[_table].length) - 1;
       }
       get first() {
-        if (this[_head] === this[_tail])
+        if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
         return this[_table].get(this[_head]);
       }
       get last() {
-        if (this[_head] === this[_tail])
+        if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
         return this[_table].get(dart.notNull(this[_tail]) - 1 & dart.notNull(this[_table].length) - 1);
       }
       get single() {
-        if (this[_head] === this[_tail])
+        if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
         if (dart.notNull(this.length) > 1)
           throw _internal.IterableElementError.tooMany();
         return this[_table].get(this[_head]);
       }
       elementAt(index) {
         core.RangeError.checkValidIndex(index, this);
         return this[_table].get(dart.notNull(this[_head]) + dart.notNull(index) & dart.notNull(this[_table].length) - 1);
       }
       toList(opts) {
@@ skipping 34 matching lines @@
               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].length) - 1) {
+        for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table].length) - 1) {
           let element = this[_table].get(i);
           if (dart.equals(element, object)) {
             this[_remove](i);
             this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
             return true;
           }
         }
         return false;
       }
       [_filterWhere](test, removeMatching) {
         let index = this[_head];
         let modificationCount = this[_modificationCount];
         let i = this[_head];
-        while (i !== this[_tail]) {
+        while (i != this[_tail]) {
           let element = this[_table].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].length) - 1;
           }
         }
       }
       removeWhere(test) {
         this[_filterWhere](test, true);
       }
       retainWhere(test) {
         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].length) - 1) {
+        if (this[_head] != this[_tail]) {
+          for (let i = this[_head]; i != this[_tail]; i = dart.notNull(i) + 1 & dart.notNull(this[_table].length) - 1) {
             this[_table].set(i, null);
           }
           this[_head] = this[_tail] = 0;
           this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         }
       }
       toString() {
         return IterableBase.iterableToFullString(this, "{", "}");
       }
       addLast(element) {
         this[_add](element);
       }
       addFirst(element) {
         this[_head] = dart.notNull(this[_head]) - 1 & dart.notNull(this[_table].length) - 1;
         this[_table].set(this[_head], element);
-        if (this[_head] === this[_tail])
+        if (this[_head] == this[_tail])
           this[_grow]();
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
       }
       removeFirst() {
-        if (this[_head] === this[_tail])
+        if (this[_head] == this[_tail])
           throw _internal.IterableElementError.noElement();
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         let result = this[_table].get(this[_head]);
         this[_table].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])
+        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].length) - 1;
         let result = this[_table].get(this[_tail]);
         this[_table].set(this[_tail], null);
         return result;
       }
       static [_isPowerOf2](number) {
-        return (dart.notNull(number) & dart.notNull(number) - 1) === 0;
+        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)
+          if (nextNumber == 0)
             return number;
           number = nextNumber;
         }
       }
       [_checkModification](expectedModificationCount) {
-        if (expectedModificationCount !== this[_modificationCount]) {
+        if (expectedModificationCount != this[_modificationCount]) {
           throw new core.ConcurrentModificationError(this);
         }
       }
       [_add](element) {
         this[_table].set(this[_tail], element);
         this[_tail] = dart.notNull(this[_tail]) + 1 & dart.notNull(this[_table].length) - 1;
-        if (this[_head] === this[_tail])
+        if (this[_head] == this[_tail])
           this[_grow]();
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
       }
       [_remove](offset) {
         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]) {
+          while (i != this[_head]) {
             let prevOffset = dart.notNull(i) - 1 & dart.notNull(mask);
             this[_table].set(i, this[_table].get(prevOffset));
             i = prevOffset;
           }
           this[_table].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]) {
+          while (i != this[_tail]) {
             let nextOffset = dart.notNull(i) + 1 & dart.notNull(mask);
             this[_table].set(i, this[_table].get(nextOffset));
             i = nextOffset;
           }
           this[_table].set(this[_tail], null);
           return offset;
         }
       }
       [_grow]() {
         let newTable = new core.List(dart.notNull(this[_table].length) * 2);
@@ skipping 42 matching lines @@
         this[_end] = queue[_tail];
         this[_modificationCount] = queue[_modificationCount];
         this[_position] = queue[_head];
         this[_current] = null;
       }
       get current() {
         return this[_current];
       }
       moveNext() {
         this[_queue]._checkModification(this[_modificationCount]);
-        if (this[_position] === this[_end]) {
+        if (this[_position] == this[_end]) {
           this[_current] = null;
           return false;
         }
         this[_current] = dart.as(this[_queue][_table].get(this[_position]), E);
         this[_position] = dart.notNull(this[_position]) + 1 & dart.notNull(this[_queue][_table].length) - 1;
         return true;
       }
     }
     return _ListQueueIterator;
   });
@@ skipping 34 matching lines @@
   let _SplayTree$ = dart.generic(function(K) {
     class _SplayTree extends core.Object {
       _SplayTree() {
         this[_dummy] = new _SplayTreeNode(null);
         this[_root] = null;
         this[_count] = 0;
         this[_modificationCount] = 0;
         this[_splayCount] = 0;
       }
       [_splay](key) {
-        if (this[_root] === null)
+        if (this[_root] == null)
           return -1;
         let left = this[_dummy];
         let right = this[_dummy];
         let current = this[_root];
         let comp = null;
         while (true) {
           comp = this[_compare](current.key, key);
           if (dart.notNull(comp) > 0) {
-            if (current.left === null)
+            if (current.left == null)
               break;
             comp = this[_compare](current.left.key, key);
             if (dart.notNull(comp) > 0) {
               let tmp = current.left;
               current.left = tmp.right;
               tmp.right = current;
               current = tmp;
-              if (current.left === null)
+              if (current.left == null)
                 break;
             }
             right.left = current;
             right = current;
             current = current.left;
           } else if (dart.notNull(comp) < 0) {
-            if (current.right === null)
+            if (current.right == null)
               break;
             comp = this[_compare](current.right.key, key);
             if (dart.notNull(comp) < 0) {
               let tmp = current.right;
               current.right = tmp.left;
               tmp.left = current;
               current = tmp;
-              if (current.right === null)
+              if (current.right == null)
                 break;
             }
             left.right = current;
             left = current;
             current = current.right;
           } else {
             break;
           }
         }
         left.right = current.left;
         right.left = current.right;
         current.left = this[_dummy].right;
         current.right = this[_dummy].left;
         this[_root] = current;
         this[_dummy].right = null;
         this[_dummy].left = null;
         this[_splayCount] = dart.notNull(this[_splayCount]) + 1;
         return comp;
       }
       [_splayMin](node) {
         let current = node;
-        while (current.left !== null) {
+        while (current.left != null) {
           let left = current.left;
           current.left = left.right;
           left.right = current;
           current = left;
         }
         return dart.as(current, _SplayTreeNode$(K));
       }
       [_splayMax](node) {
         let current = node;
-        while (current.right !== null) {
+        while (current.right != null) {
           let right = current.right;
           current.right = right.left;
           right.left = current;
           current = right;
         }
         return dart.as(current, _SplayTreeNode$(K));
       }
       [_remove](key) {
-        if (this[_root] === null)
+        if (this[_root] == null)
           return null;
         let comp = this[_splay](key);
-        if (comp !== 0)
+        if (comp != 0)
           return null;
         let result = this[_root];
         this[_count] = dart.notNull(this[_count]) - 1;
-        if (this[_root].left === null) {
+        if (this[_root].left == null) {
           this[_root] = this[_root].right;
         } else {
           let right = this[_root].right;
           this[_root] = this[_splayMax](this[_root].left);
           this[_root].right = right;
         }
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         return result;
       }
       [_addNewRoot](node, comp) {
         this[_count] = dart.notNull(this[_count]) + 1;
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
-        if (this[_root] === null) {
+        if (this[_root] == null) {
           this[_root] = node;
           return;
         }
         if (dart.notNull(comp) < 0) {
           node.left = this[_root];
           node.right = this[_root].right;
           this[_root].right = null;
         } else {
           node.right = this[_root];
           node.left = this[_root].left;
           this[_root].left = null;
         }
         this[_root] = node;
       }
       get [_first]() {
-        if (this[_root] === null)
+        if (this[_root] == null)
           return null;
         this[_root] = this[_splayMin](this[_root]);
         return this[_root];
       }
       get [_last]() {
-        if (this[_root] === null)
+        if (this[_root] == null)
           return null;
         this[_root] = this[_splayMax](this[_root]);
         return this[_root];
       }
       [_clear]() {
         this[_root] = null;
         this[_count] = 0;
         this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
       }
     }
@@ skipping 12 matching lines @@
   let _comparator = Symbol('_comparator');
   let _validKey = Symbol('_validKey');
   let _internal$ = Symbol('_internal');
   let SplayTreeMap$ = dart.generic(function(K, V) {
     class SplayTreeMap extends _SplayTree$(K) {
       SplayTreeMap(compare, isValidKey) {
         if (compare === void 0)
           compare = null;
         if (isValidKey === void 0)
           isValidKey = null;
-        this[_comparator] = dart.as(compare === null ? core.Comparable.compare : compare, core.Comparator);
-        this[_validKey] = dart.as(isValidKey !== null ? isValidKey : (v) => dart.is(v, K), _Predicate);
+        this[_comparator] = dart.as(compare == null ? core.Comparable.compare : compare, core.Comparator);
+        this[_validKey] = dart.as(isValidKey != null ? isValidKey : (v) => dart.is(v, K), _Predicate);
         super._SplayTree();
       }
       from(other, compare, isValidKey) {
         if (compare === void 0)
           compare = null;
         if (isValidKey === void 0)
           isValidKey = null;
         let result = new SplayTreeMap();
         other.forEach((k, v) => {
           result.set(k, dart.as(v, V));
@@ skipping 20 matching lines @@
       }
       [_compare](key1, key2) {
         return this[_comparator](key1, key2);
       }
       [_internal$]() {
         this[_comparator] = null;
         this[_validKey] = null;
         super._SplayTree();
       }
       get(key) {
-        if (key === null)
+        if (key == null)
           throw new core.ArgumentError(key);
         if (!dart.notNull(dart.dinvokef(this[_validKey], key)))
           return null;
-        if (this[_root] !== null) {
+        if (this[_root] != null) {
           let comp = this[_splay](dart.as(key, K));
-          if (comp === 0) {
+          if (comp == 0) {
             let mapRoot = dart.as(this[_root], _SplayTreeMapNode);
             return dart.as(mapRoot.value, V);
           }
         }
         return null;
       }
       remove(key) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], key)))
           return null;
         let mapRoot = dart.as(this[_remove](dart.as(key, K)), _SplayTreeMapNode);
-        if (mapRoot !== null)
+        if (mapRoot != null)
           return dart.as(mapRoot.value, V);
         return null;
       }
       set(key, value) {
-        if (key === null)
+        if (key == null)
           throw new core.ArgumentError(key);
         let comp = this[_splay](key);
-        if (comp === 0) {
+        if (comp == 0) {
           let mapRoot = dart.as(this[_root], _SplayTreeMapNode);
           mapRoot.value = value;
           return;
         }
         this[_addNewRoot](dart.as(new _SplayTreeMapNode(key, value), _SplayTreeNode$(K)), comp);
       }
       putIfAbsent(key, ifAbsent) {
-        if (key === null)
+        if (key == null)
           throw new core.ArgumentError(key);
         let comp = this[_splay](key);
-        if (comp === 0) {
+        if (comp == 0) {
           let mapRoot = dart.as(this[_root], _SplayTreeMapNode);
           return dart.as(mapRoot.value, V);
         }
         let modificationCount = this[_modificationCount];
         let splayCount = this[_splayCount];
         let value = ifAbsent();
-        if (modificationCount !== this[_modificationCount]) {
+        if (modificationCount != this[_modificationCount]) {
           throw new core.ConcurrentModificationError(this);
         }
-        if (splayCount !== this[_splayCount]) {
+        if (splayCount != this[_splayCount]) {
           comp = this[_splay](key);
-          dart.assert(comp !== 0);
+          dart.assert(comp != 0);
         }
         this[_addNewRoot](dart.as(new _SplayTreeMapNode(key, value), _SplayTreeNode$(K)), comp);
         return value;
       }
       addAll(other) {
         other.forEach(((key, value) => {
           this.set(key, value);
         }).bind(this));
       }
       get isEmpty() {
-        return this[_root] === null;
+        return this[_root] == null;
       }
       get isNotEmpty() {
         return !dart.notNull(this.isEmpty);
       }
       forEach(f) {
         let nodes = new _SplayTreeNodeIterator(this);
         while (nodes.moveNext()) {
           let node = dart.as(nodes.current, _SplayTreeMapNode$(K, V));
           f(node.key, node.value);
         }
       }
       get length() {
         return this[_count];
       }
       clear() {
         this[_clear]();
       }
       containsKey(key) {
-        return dart.notNull(dart.dinvokef(this[_validKey], key)) && this[_splay](dart.as(key, K)) === 0;
+        return dart.notNull(dart.dinvokef(this[_validKey], key)) && this[_splay](dart.as(key, K)) == 0;
       }
       containsValue(value) {
         let found = false;
         let initialSplayCount = this[_splayCount];
         // Function visit: (_SplayTreeMapNode<dynamic, dynamic>) → bool
         function visit(node) {
-          while (node !== null) {
+          while (node != null) {
             if (dart.equals(node.value, value))
               return true;
-            if (initialSplayCount !== this[_splayCount]) {
+            if (initialSplayCount != this[_splayCount]) {
               throw new core.ConcurrentModificationError(this);
             }
-            if (dart.notNull(node.right !== null) && dart.notNull(visit(dart.as(node.right, _SplayTreeMapNode))))
+            if (dart.notNull(node.right != null) && dart.notNull(visit(dart.as(node.right, _SplayTreeMapNode))))
               return true;
             node = dart.as(node.left, _SplayTreeMapNode);
           }
           return false;
         }
         return visit(dart.as(this[_root], _SplayTreeMapNode));
       }
       get keys() {
         return new _SplayTreeKeyIterable(this);
       }
       get values() {
         return new _SplayTreeValueIterable(this);
       }
       toString() {
         return Maps.mapToString(this);
       }
       firstKey() {
-        if (this[_root] === null)
+        if (this[_root] == null)
           return null;
         return dart.as(this[_first].key, K);
       }
       lastKey() {
-        if (this[_root] === null)
+        if (this[_root] == null)
           return null;
         return dart.as(this[_last].key, K);
       }
       lastKeyBefore(key) {
-        if (key === null)
+        if (key == null)
           throw new core.ArgumentError(key);
-        if (this[_root] === null)
+        if (this[_root] == null)
           return null;
         let comp = this[_splay](key);
         if (dart.notNull(comp) < 0)
           return this[_root].key;
         let node = this[_root].left;
-        if (node === null)
+        if (node == null)
           return null;
-        while (node.right !== null) {
+        while (node.right != null) {
           node = node.right;
         }
         return node.key;
       }
       firstKeyAfter(key) {
-        if (key === null)
+        if (key == null)
           throw new core.ArgumentError(key);
-        if (this[_root] === null)
+        if (this[_root] == null)
           return null;
         let comp = this[_splay](key);
         if (dart.notNull(comp) > 0)
           return this[_root].key;
         let node = this[_root].right;
-        if (node === null)
+        if (node == null)
           return null;
-        while (node.left !== null) {
+        while (node.left != null) {
           node = node.left;
         }
         return node.key;
       }
     }
     dart.defineNamedConstructor(SplayTreeMap, 'from');
     dart.defineNamedConstructor(SplayTreeMap, 'fromIterable');
     dart.defineNamedConstructor(SplayTreeMap, 'fromIterables');
     dart.defineNamedConstructor(SplayTreeMap, _internal$);
     return SplayTreeMap;
@@ skipping 14 matching lines @@
         this[_splayCount] = tree[_splayCount];
         this[_currentNode] = null;
         this[_findLeftMostDescendent](tree[_root]);
       }
       startAt(tree, startKey) {
         this[_workList] = new core.List$(_SplayTreeNode).from([]);
         this[_tree] = tree;
         this[_modificationCount] = tree[_modificationCount];
         this[_splayCount] = null;
         this[_currentNode] = null;
-        if (tree[_root] === 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].add(tree[_root]);
         }
       }
       get current() {
-        if (this[_currentNode] === null)
+        if (this[_currentNode] == null)
           return null;
         return this[_getValue](this[_currentNode]);
       }
       [_findLeftMostDescendent](node) {
-        while (node !== null) {
+        while (node != null) {
           this[_workList].add(node);
           node = node.left;
         }
       }
       [_rebuildWorkList](currentNode) {
         dart.assert(!dart.notNull(this[_workList].isEmpty));
         this[_workList].clear();
-        if (currentNode === null) {
+        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].isEmpty));
         }
       }
       moveNext() {
-        if (this[_modificationCount] !== this[_tree][_modificationCount]) {
+        if (this[_modificationCount] != this[_tree][_modificationCount]) {
           throw new core.ConcurrentModificationError(this[_tree]);
         }
         if (this[_workList].isEmpty) {
           this[_currentNode] = null;
           return false;
         }
-        if (this[_tree][_splayCount] !== this[_splayCount] && dart.notNull(this[_currentNode] !== null)) {
+        if (this[_tree][_splayCount] != this[_splayCount] && dart.notNull(this[_currentNode] != null)) {
           this[_rebuildWorkList](this[_currentNode]);
         }
         this[_currentNode] = this[_workList].removeLast();
         this[_findLeftMostDescendent](this[_currentNode].right);
         return true;
       }
     }
     dart.defineNamedConstructor(_SplayTreeIterator, 'startAt');
     return _SplayTreeIterator;
   });
   let _SplayTreeIterator = _SplayTreeIterator$(dart.dynamic);
   let _SplayTreeKeyIterable$ = dart.generic(function(K) {
     class _SplayTreeKeyIterable extends IterableBase$(K) {
       _SplayTreeKeyIterable(tree$) {
         this[_tree] = tree$;
         super.IterableBase();
       }
       get length() {
         return this[_tree][_count];
       }
       get isEmpty() {
-        return this[_tree][_count] === 0;
+        return this[_tree][_count] == 0;
       }
       get iterator() {
         return new _SplayTreeKeyIterator(this[_tree]);
       }
       toSet() {
         let setOrMap = this[_tree];
         let set = new SplayTreeSet(dart.as(setOrMap[_comparator], dart.throw_("Unimplemented type (K, K) → int")), dart.as(setOrMap[_validKey], dart.throw_("Unimplemented type (dynamic) → bool")));
         set[_count] = this[_tree][_count];
         set[_root] = set._copyNode(this[_tree][_root]);
         return set;
       }
     }
     return _SplayTreeKeyIterable;
   });
   let _SplayTreeKeyIterable = _SplayTreeKeyIterable$(dart.dynamic);
   let _SplayTreeValueIterable$ = dart.generic(function(K, V) {
     class _SplayTreeValueIterable extends IterableBase$(V) {
       _SplayTreeValueIterable(map$) {
         this[_map] = map$;
         super.IterableBase();
       }
       get length() {
         return this[_map][_count];
       }
       get isEmpty() {
-        return this[_map][_count] === 0;
+        return this[_map][_count] == 0;
       }
       get iterator() {
         return new _SplayTreeValueIterator(this[_map]);
       }
     }
     return _SplayTreeValueIterable;
   });
   let _SplayTreeValueIterable = _SplayTreeValueIterable$(dart.dynamic, dart.dynamic);
   let _SplayTreeKeyIterator$ = dart.generic(function(K) {
     class _SplayTreeKeyIterator extends _SplayTreeIterator$(K) {
@@ skipping 37 matching lines @@
   let _SplayTreeNodeIterator = _SplayTreeNodeIterator$(dart.dynamic);
   let _clone = Symbol('_clone');
   let _copyNode = Symbol('_copyNode');
   let SplayTreeSet$ = dart.generic(function(E) {
     class SplayTreeSet extends dart.mixin(_SplayTree$(E), IterableMixin$(E), SetMixin$(E)) {
       SplayTreeSet(compare, isValidKey) {
         if (compare === void 0)
           compare = null;
         if (isValidKey === void 0)
           isValidKey = null;
-        this[_comparator] = dart.as(compare === null ? core.Comparable.compare : compare, core.Comparator);
-        this[_validKey] = dart.as(isValidKey !== null ? isValidKey : (v) => dart.is(v, E), _Predicate);
+        this[_comparator] = dart.as(compare == null ? core.Comparable.compare : compare, core.Comparator);
+        this[_validKey] = dart.as(isValidKey != null ? isValidKey : (v) => dart.is(v, E), _Predicate);
         super._SplayTree();
       }
       from(elements, compare, isValidKey) {
         if (compare === void 0)
           compare = null;
         if (isValidKey === void 0)
           isValidKey = null;
         let result = new SplayTreeSet(compare, isValidKey);
         for (let element of elements) {
           result.add(element);
         }
         return result;
       }
       [_compare](e1, e2) {
         return dart.dinvokef(this[_comparator], e1, e2);
       }
       get iterator() {
         return new _SplayTreeKeyIterator(this);
       }
       get length() {
         return this[_count];
       }
       get isEmpty() {
-        return this[_root] === null;
+        return this[_root] == null;
       }
       get isNotEmpty() {
-        return this[_root] !== null;
+        return this[_root] != null;
       }
       get first() {
-        if (this[_count] === 0)
+        if (this[_count] == 0)
           throw _internal.IterableElementError.noElement();
         return dart.as(this[_first].key, E);
       }
       get last() {
-        if (this[_count] === 0)
+        if (this[_count] == 0)
           throw _internal.IterableElementError.noElement();
         return dart.as(this[_last].key, E);
       }
       get single() {
-        if (this[_count] === 0)
+        if (this[_count] == 0)
           throw _internal.IterableElementError.noElement();
         if (dart.notNull(this[_count]) > 1)
           throw _internal.IterableElementError.tooMany();
         return this[_root].key;
       }
       contains(object) {
-        return dart.notNull(dart.dinvokef(this[_validKey], object)) && this[_splay](dart.as(object, E)) === 0;
+        return dart.notNull(dart.dinvokef(this[_validKey], object)) && this[_splay](dart.as(object, E)) == 0;
       }
       add(element) {
         let compare = this[_splay](element);
-        if (compare === 0)
+        if (compare == 0)
           return false;
         this[_addNewRoot](dart.as(new _SplayTreeNode(element), _SplayTreeNode$(E)), compare);
         return true;
       }
       remove(object) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], object)))
           return false;
-        return this[_remove](dart.as(object, E)) !== null;
+        return this[_remove](dart.as(object, E)) != null;
       }
       addAll(elements) {
         for (let element of elements) {
           let compare = this[_splay](element);
-          if (compare !== 0) {
+          if (compare != 0) {
             this[_addNewRoot](dart.as(new _SplayTreeNode(element), _SplayTreeNode$(E)), compare);
           }
         }
       }
       removeAll(elements) {
         for (let element of elements) {
           if (dart.dinvokef(this[_validKey], element))
             this[_remove](dart.as(element, E));
         }
       }
       retainAll(elements) {
         let retainSet = new SplayTreeSet(dart.closureWrap(this[_comparator], "(E, E) → int"), this[_validKey]);
         let modificationCount = this[_modificationCount];
         for (let object of elements) {
-          if (modificationCount !== this[_modificationCount]) {
+          if (modificationCount != this[_modificationCount]) {
             throw new core.ConcurrentModificationError(this);
           }
-          if (dart.notNull(dart.dinvokef(this[_validKey], object)) && this[_splay](dart.as(object, E)) === 0)
+          if (dart.notNull(dart.dinvokef(this[_validKey], object)) && this[_splay](dart.as(object, E)) == 0)
             retainSet.add(this[_root].key);
         }
-        if (retainSet[_count] !== this[_count]) {
+        if (retainSet[_count] != this[_count]) {
           this[_root] = retainSet[_root];
           this[_count] = retainSet[_count];
           this[_modificationCount] = dart.notNull(this[_modificationCount]) + 1;
         }
       }
       lookup(object) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], object)))
           return null;
         let comp = this[_splay](dart.as(object, E));
-        if (comp !== 0)
+        if (comp != 0)
           return null;
         return this[_root].key;
       }
       intersection(other) {
         let result = new SplayTreeSet(dart.closureWrap(this[_comparator], "(E, E) → int"), this[_validKey]);
         for (let element of this) {
           if (other.contains(element))
             result.add(element);
         }
         return result;
@@ skipping 12 matching lines @@
           return _;
         }).bind(this)(this[_clone]());
       }
       [_clone]() {
         let set = new SplayTreeSet(dart.closureWrap(this[_comparator], "(E, E) → int"), this[_validKey]);
         set[_count] = this[_count];
         set[_root] = this[_copyNode](this[_root]);
         return set;
       }
       [_copyNode](node) {
-        if (node === null)
+        if (node == null)
           return null;
         return ((_) => {
           _.left = this[_copyNode](node.left);
           _.right = this[_copyNode](node.right);
           return _;
         }).bind(this)(new _SplayTreeNode(node.key));
       }
       clear() {
         this[_clear]();
       }
@@ skipping 33 matching lines @@
         this[_length] = 0;
         this[_strings] = null;
         this[_nums] = null;
         this[_rest] = null;
         this[_keys] = null;
       }
       get length() {
         return this[_length];
       }
       get isEmpty() {
-        return this[_length] === 0;
+        return this[_length] == 0;
       }
       get isNotEmpty() {
         return !dart.notNull(this.isEmpty);
       }
       get keys() {
         return new HashMapKeyIterable(this);
       }
       get values() {
         return new _internal.MappedIterable(this.keys, dart.closureWrap(((each) => this.get(each)).bind(this), "(K) → V"));
       }
       containsKey(key) {
         if (_HashMap[_isStringKey](key)) {
           let strings = this[_strings];
-          return strings === null ? false : _HashMap[_hasTableEntry](strings, key);
+          return strings == null ? false : _HashMap[_hasTableEntry](strings, key);
         } else if (_HashMap[_isNumericKey](key)) {
           let nums = this[_nums];
-          return nums === null ? false : _HashMap[_hasTableEntry](nums, key);
+          return nums == null ? false : _HashMap[_hasTableEntry](nums, key);
         } else {
           return this[_containsKey](key);
         }
       }
       [_containsKey](key) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           return false;
         let bucket = this[_getBucket](rest, key);
         return dart.notNull(this[_findBucketIndex](bucket, key)) >= 0;
       }
       containsValue(value) {
         return this[_computeKeys]().any(((each) => dart.equals(this.get(each), value)).bind(this));
       }
       addAll(other) {
         other.forEach(((key, value) => {
           this.set(key, value);
         }).bind(this));
       }
       get(key) {
         if (_HashMap[_isStringKey](key)) {
           let strings = this[_strings];
-          return dart.as(strings === null ? null : _HashMap[_getTableEntry](strings, key), V);
+          return dart.as(strings == null ? null : _HashMap[_getTableEntry](strings, key), V);
         } else if (_HashMap[_isNumericKey](key)) {
           let nums = this[_nums];
-          return dart.as(nums === null ? null : _HashMap[_getTableEntry](nums, key), V);
+          return dart.as(nums == null ? null : _HashMap[_getTableEntry](nums, key), V);
         } else {
           return this[_get](key);
         }
       }
       [_get](key) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           return null;
         let bucket = this[_getBucket](rest, key);
         let index = this[_findBucketIndex](bucket, key);
         return dart.as(dart.notNull(index) < 0 ? null : bucket[dart.notNull(index) + 1], V);
       }
       set(key, value) {
         if (_HashMap[_isStringKey](key)) {
           let strings = this[_strings];
-          if (strings === null)
+          if (strings == null)
             this[_strings] = strings = _HashMap[_newHashTable]();
           this[_addHashTableEntry](strings, key, value);
         } else if (_HashMap[_isNumericKey](key)) {
           let nums = this[_nums];
-          if (nums === null)
+          if (nums == null)
             this[_nums] = nums = _HashMap[_newHashTable]();
           this[_addHashTableEntry](nums, key, value);
         } else {
           this[_set](key, value);
         }
       }
       [_set](key, value) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           this[_rest] = rest = _HashMap[_newHashTable]();
         let hash = this[_computeHashCode](key);
         let bucket = rest[hash];
-        if (bucket === null) {
+        if (bucket == null) {
           _HashMap[_setTableEntry](rest, hash, [key, value]);
           this[_length] = dart.notNull(this[_length]) + 1;
           this[_keys] = null;
         } else {
           let index = this[_findBucketIndex](bucket, key);
           if (dart.notNull(index) >= 0) {
             bucket[dart.notNull(index) + 1] = value;
           } else {
             bucket.push(key, value);
             this[_length] = dart.notNull(this[_length]) + 1;
@@ skipping 12 matching lines @@
         if (_HashMap[_isStringKey](key)) {
           return this[_removeHashTableEntry](this[_strings], key);
         } else if (_HashMap[_isNumericKey](key)) {
           return this[_removeHashTableEntry](this[_nums], key);
         } else {
           return this[_remove](key);
         }
       }
       [_remove](key) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           return null;
         let bucket = this[_getBucket](rest, key);
         let index = this[_findBucketIndex](bucket, key);
         if (dart.notNull(index) < 0)
           return null;
         this[_length] = dart.notNull(this[_length]) - 1;
         this[_keys] = null;
         return dart.as(bucket.splice(index, 2)[1], V);
       }
       clear() {
         if (dart.notNull(this[_length]) > 0) {
           this[_strings] = this[_nums] = this[_rest] = this[_keys] = null;
           this[_length] = 0;
         }
       }
       forEach(action) {
         let keys = this[_computeKeys]();
         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)
+        if (this[_keys] != null)
           return this[_keys];
         let result = new core.List(this[_length]);
         let index = 0;
         let strings = this[_strings];
-        if (strings !== null) {
+        if (strings != null) {
           let names = Object.getOwnPropertyNames(strings);
           let entries = names.length;
           for (let i = 0; dart.notNull(i) < dart.notNull(entries); i = dart.notNull(i) + 1) {
             let key = names[i];
             result[index] = key;
             index = dart.notNull(index) + 1;
           }
         }
         let nums = this[_nums];
-        if (nums !== null) {
+        if (nums != null) {
           let names = Object.getOwnPropertyNames(nums);
           let entries = names.length;
           for (let i = 0; dart.notNull(i) < dart.notNull(entries); i = dart.notNull(i) + 1) {
             let key = +names[i];
             result[index] = key;
             index = dart.notNull(index) + 1;
           }
         }
         let rest = this[_rest];
-        if (rest !== null) {
+        if (rest != null) {
           let names = Object.getOwnPropertyNames(rest);
           let entries = names.length;
           for (let i = 0; dart.notNull(i) < dart.notNull(entries); i = dart.notNull(i) + 1) {
             let key = names[i];
             let bucket = rest[key];
             let length = bucket.length;
             for (let i = 0; dart.notNull(i) < dart.notNull(length); i = 2) {
               let key = bucket[i];
               result[index] = key;
               index = dart.notNull(index) + 1;
             }
           }
         }
-        dart.assert(index === this[_length]);
+        dart.assert(index == this[_length]);
         return this[_keys] = result;
       }
       [_addHashTableEntry](table, key, value) {
         if (!dart.notNull(_HashMap[_hasTableEntry](table, key))) {
           this[_length] = dart.notNull(this[_length]) + 1;
           this[_keys] = null;
         }
         _HashMap[_setTableEntry](table, key, value);
       }
       [_removeHashTableEntry](table, key) {
-        if (dart.notNull(table !== null) && dart.notNull(_HashMap[_hasTableEntry](table, key))) {
+        if (dart.notNull(table != null) && dart.notNull(_HashMap[_hasTableEntry](table, key))) {
           let value = dart.as(_HashMap[_getTableEntry](table, key), V);
           _HashMap[_deleteTableEntry](table, key);
           this[_length] = dart.notNull(this[_length]) - 1;
           this[_keys] = null;
           return value;
         } else {
           return null;
         }
       }
       static [_isStringKey](key) {
         return dart.notNull(typeof key == 'string') && dart.notNull(!dart.equals(key, '__proto__'));
       }
       static [_isNumericKey](key) {
         return dart.notNull(dart.is(key, core.num)) && (key & 0x3ffffff) === key;
       }
       [_computeHashCode](key) {
         return dart.dload(key, 'hashCode') & 0x3ffffff;
       }
       static [_hasTableEntry](table, key) {
         let entry = table[key];
-        return entry !== null;
+        return entry != null;
       }
       static [_getTableEntry](table, key) {
         let entry = table[key];
         return entry === table ? null : entry;
       }
       static [_setTableEntry](table, key, value) {
-        if (value === null) {
+        if (value == null) {
           table[key] = table;
         } else {
           table[key] = value;
         }
       }
       static [_deleteTableEntry](table, key) {
         delete table[key];
       }
       [_getBucket](table, key) {
         let hash = this[_computeHashCode](key);
         return dart.as(table[hash], core.List);
       }
       [_findBucketIndex](bucket, key) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = 2) {
           if (dart.equals(bucket[i], key))
             return i;
         }
         return -1;
       }
       static [_newHashTable]() {
         let table = Object.create(null);
         let temporaryKey = '<non-identifier-key>';
         _HashMap[_setTableEntry](table, temporaryKey, table);
         _HashMap[_deleteTableEntry](table, temporaryKey);
         return table;
       }
     }
     return _HashMap;
   });
   let _HashMap = _HashMap$(dart.dynamic, dart.dynamic);
   let _IdentityHashMap$ = dart.generic(function(K, V) {
     class _IdentityHashMap extends _HashMap$(K, V) {
       [_computeHashCode](key) {
         return core.identityHashCode(key) & 0x3ffffff;
       }
       [_findBucketIndex](bucket, key) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = 2) {
           if (core.identical(bucket[i], key))
             return i;
         }
         return -1;
       }
     }
     return _IdentityHashMap;
   });
   let _IdentityHashMap = _IdentityHashMap$(dart.dynamic, dart.dynamic);
   let _equals = Symbol('_equals');
   let _hashCode = Symbol('_hashCode');
   let _CustomHashMap$ = dart.generic(function(K, V) {
     class _CustomHashMap extends _HashMap$(K, V) {
       _CustomHashMap(equals$, hashCode$, validKey) {
         this[_equals] = equals$;
         this[_hashCode] = hashCode$;
-        this[_validKey] = dart.as(validKey !== null ? validKey : (v) => dart.is(v, K), _Predicate);
+        this[_validKey] = dart.as(validKey != null ? validKey : (v) => dart.is(v, K), _Predicate);
         super._HashMap();
       }
       get(key) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], key)))
           return null;
         return super._get(key);
       }
       set(key, value) {
         super._set(key, value);
       }
       containsKey(key) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], key)))
           return false;
         return super._containsKey(key);
       }
       remove(key) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], key)))
           return null;
         return super._remove(key);
       }
       [_computeHashCode](key) {
         return this[_hashCode](dart.as(key, K)) & 0x3ffffff;
       }
       [_findBucketIndex](bucket, key) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = 2) {
           if (this[_equals](dart.as(bucket[i], K), dart.as(key, K)))
             return i;
         }
         return -1;
       }
       toString() {
         return Maps.mapToString(this);
@@ skipping 77 matching lines @@
         this[_nums] = null;
         this[_rest] = null;
         this[_first] = null;
         this[_last] = null;
         this[_modifications] = 0;
       }
       get length() {
         return this[_length];
       }
       get isEmpty() {
-        return this[_length] === 0;
+        return this[_length] == 0;
       }
       get isNotEmpty() {
         return !dart.notNull(this.isEmpty);
       }
       get keys() {
         return new LinkedHashMapKeyIterable(this);
       }
       get values() {
         return new _internal.MappedIterable(this.keys, dart.closureWrap(((each) => this.get(each)).bind(this), "(K) → V"));
       }
       containsKey(key) {
         if (_LinkedHashMap[_isStringKey](key)) {
           let strings = this[_strings];
-          if (strings === null)
+          if (strings == null)
             return false;
           let cell = dart.as(_LinkedHashMap[_getTableEntry](strings, key), LinkedHashMapCell);
-          return cell !== null;
+          return cell != null;
         } else if (_LinkedHashMap[_isNumericKey](key)) {
           let nums = this[_nums];
-          if (nums === null)
+          if (nums == null)
             return false;
           let cell = dart.as(_LinkedHashMap[_getTableEntry](nums, key), LinkedHashMapCell);
-          return cell !== null;
+          return cell != null;
         } else {
           return this[_containsKey](key);
         }
       }
       [_containsKey](key) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           return false;
         let bucket = this[_getBucket](rest, key);
         return dart.notNull(this[_findBucketIndex](bucket, key)) >= 0;
       }
       containsValue(value) {
         return this.keys.any(dart.closureWrap(((each) => dart.equals(this.get(each), value)).bind(this), "(K) → bool"));
       }
       addAll(other) {
         other.forEach(((key, value) => {
           this.set(key, value);
         }).bind(this));
       }
       get(key) {
         if (_LinkedHashMap[_isStringKey](key)) {
           let strings = this[_strings];
-          if (strings === null)
+          if (strings == null)
             return null;
           let cell = dart.as(_LinkedHashMap[_getTableEntry](strings, key), LinkedHashMapCell);
-          return dart.as(cell === null ? null : cell[_value], V);
+          return dart.as(cell == null ? null : cell[_value], V);
         } else if (_LinkedHashMap[_isNumericKey](key)) {
           let nums = this[_nums];
-          if (nums === null)
+          if (nums == null)
             return null;
           let cell = dart.as(_LinkedHashMap[_getTableEntry](nums, key), LinkedHashMapCell);
-          return dart.as(cell === null ? null : cell[_value], V);
+          return dart.as(cell == null ? null : cell[_value], V);
         } else {
           return this[_get](key);
         }
       }
       [_get](key) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           return null;
         let bucket = this[_getBucket](rest, key);
         let index = this[_findBucketIndex](bucket, key);
         if (dart.notNull(index) < 0)
           return null;
         let cell = dart.as(bucket[index], LinkedHashMapCell);
         return dart.as(cell[_value], V);
       }
       set(key, value) {
         if (_LinkedHashMap[_isStringKey](key)) {
           let strings = this[_strings];
-          if (strings === null)
+          if (strings == null)
             this[_strings] = strings = _LinkedHashMap[_newHashTable]();
           this[_addHashTableEntry](strings, key, value);
         } else if (_LinkedHashMap[_isNumericKey](key)) {
           let nums = this[_nums];
-          if (nums === null)
+          if (nums == null)
             this[_nums] = nums = _LinkedHashMap[_newHashTable]();
           this[_addHashTableEntry](nums, key, value);
         } else {
           this[_set](key, value);
         }
       }
       [_set](key, value) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           this[_rest] = rest = _LinkedHashMap[_newHashTable]();
         let hash = this[_computeHashCode](key);
         let bucket = rest[hash];
-        if (bucket === null) {
+        if (bucket == null) {
           let cell = this[_newLinkedCell](key, value);
           _LinkedHashMap[_setTableEntry](rest, hash, [cell]);
         } else {
           let index = this[_findBucketIndex](bucket, key);
           if (dart.notNull(index) >= 0) {
             let cell = dart.as(bucket[index], LinkedHashMapCell);
             cell[_value] = value;
           } else {
             let cell = this[_newLinkedCell](key, value);
             bucket.push(cell);
@@ skipping 11 matching lines @@
         if (_LinkedHashMap[_isStringKey](key)) {
           return this[_removeHashTableEntry](this[_strings], key);
         } else if (_LinkedHashMap[_isNumericKey](key)) {
           return this[_removeHashTableEntry](this[_nums], key);
         } else {
           return this[_remove](key);
         }
       }
       [_remove](key) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           return null;
         let bucket = this[_getBucket](rest, key);
         let index = this[_findBucketIndex](bucket, key);
         if (dart.notNull(index) < 0)
           return null;
         let cell = dart.as(bucket.splice(index, 1)[0], LinkedHashMapCell);
         this[_unlinkCell](cell);
         return dart.as(cell[_value], V);
       }
       clear() {
         if (dart.notNull(this[_length]) > 0) {
           this[_strings] = this[_nums] = this[_rest] = this[_first] = this[_last] = null;
           this[_length] = 0;
           this[_modified]();
         }
       }
       forEach(action) {
         let cell = this[_first];
         let modifications = this[_modifications];
-        while (cell !== null) {
+        while (cell != null) {
           action(dart.as(cell[_key], K), dart.as(cell[_value], V));
-          if (modifications !== this[_modifications]) {
+          if (modifications != this[_modifications]) {
             throw new core.ConcurrentModificationError(this);
           }
           cell = cell[_next];
         }
       }
       [_addHashTableEntry](table, key, value) {
         let cell = dart.as(_LinkedHashMap[_getTableEntry](table, key), LinkedHashMapCell);
-        if (cell === null) {
+        if (cell == null) {
           _LinkedHashMap[_setTableEntry](table, key, this[_newLinkedCell](key, value));
         } else {
           cell[_value] = value;
         }
       }
       [_removeHashTableEntry](table, key) {
-        if (table === null)
+        if (table == null)
           return null;
         let cell = dart.as(_LinkedHashMap[_getTableEntry](table, key), LinkedHashMapCell);
-        if (cell === null)
+        if (cell == null)
           return null;
         this[_unlinkCell](cell);
         _LinkedHashMap[_deleteTableEntry](table, key);
         return dart.as(cell[_value], V);
       }
       [_modified]() {
         this[_modifications] = dart.notNull(this[_modifications]) + 1 & 67108863;
       }
       [_newLinkedCell](key, value) {
         let cell = new LinkedHashMapCell(key, value);
-        if (this[_first] === null) {
+        if (this[_first] == null) {
           this[_first] = this[_last] = cell;
         } else {
           let last = this[_last];
           cell[_previous] = last;
           this[_last] = last[_next] = cell;
         }
         this[_length] = dart.notNull(this[_length]) + 1;
         this[_modified]();
         return cell;
       }
       [_unlinkCell](cell) {
         let previous = cell[_previous];
         let next = cell[_next];
-        if (previous === null) {
+        if (previous == null) {
           dart.assert(dart.equals(cell, this[_first]));
           this[_first] = next;
         } else {
           previous[_next] = next;
         }
-        if (next === null) {
+        if (next == null) {
           dart.assert(dart.equals(cell, this[_last]));
           this[_last] = previous;
         } else {
           next[_previous] = previous;
         }
         this[_length] = dart.notNull(this[_length]) - 1;
         this[_modified]();
       }
       static [_isStringKey](key) {
         return dart.notNull(typeof key == 'string') && dart.notNull(!dart.equals(key, '__proto__'));
       }
       static [_isNumericKey](key) {
         return dart.notNull(dart.is(key, core.num)) && (key & 0x3ffffff) === key;
       }
       [_computeHashCode](key) {
         return dart.dload(key, 'hashCode') & 0x3ffffff;
       }
       static [_getTableEntry](table, key) {
         return table[key];
       }
       static [_setTableEntry](table, key, value) {
-        dart.assert(value !== null);
+        dart.assert(value != null);
         table[key] = value;
       }
       static [_deleteTableEntry](table, key) {
         delete table[key];
       }
       [_getBucket](table, key) {
         let hash = this[_computeHashCode](key);
         return dart.as(table[hash], core.List);
       }
       [_findBucketIndex](bucket, key) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let cell = dart.as(bucket[i], LinkedHashMapCell);
           if (dart.equals(cell[_key], key))
             return i;
         }
         return -1;
       }
       static [_newHashTable]() {
         let table = Object.create(null);
         let temporaryKey = '<non-identifier-key>';
         _LinkedHashMap[_setTableEntry](table, temporaryKey, table);
         _LinkedHashMap[_deleteTableEntry](table, temporaryKey);
         return table;
       }
       toString() {
         return Maps.mapToString(this);
       }
     }
     return _LinkedHashMap;
   });
   let _LinkedHashMap = _LinkedHashMap$(dart.dynamic, dart.dynamic);
   let _LinkedIdentityHashMap$ = dart.generic(function(K, V) {
     class _LinkedIdentityHashMap extends _LinkedHashMap$(K, V) {
       [_computeHashCode](key) {
         return core.identityHashCode(key) & 0x3ffffff;
       }
       [_findBucketIndex](bucket, key) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let cell = dart.as(bucket[i], LinkedHashMapCell);
           if (core.identical(cell[_key], key))
             return i;
         }
         return -1;
       }
     }
     return _LinkedIdentityHashMap;
   });
   let _LinkedIdentityHashMap = _LinkedIdentityHashMap$(dart.dynamic, dart.dynamic);
   let _LinkedCustomHashMap$ = dart.generic(function(K, V) {
     class _LinkedCustomHashMap extends _LinkedHashMap$(K, V) {
       _LinkedCustomHashMap(equals$, hashCode$, validKey) {
         this[_equals] = equals$;
         this[_hashCode] = hashCode$;
-        this[_validKey] = dart.as(validKey !== null ? validKey : (v) => dart.is(v, K), _Predicate);
+        this[_validKey] = dart.as(validKey != null ? validKey : (v) => dart.is(v, K), _Predicate);
         super._LinkedHashMap();
       }
       get(key) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], key)))
           return null;
         return super._get(key);
       }
       set(key, value) {
         super._set(key, value);
       }
       containsKey(key) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], key)))
           return false;
         return super._containsKey(key);
       }
       remove(key) {
         if (!dart.notNull(dart.dinvokef(this[_validKey], key)))
           return null;
         return super._remove(key);
       }
       [_computeHashCode](key) {
         return this[_hashCode](dart.as(key, K)) & 0x3ffffff;
       }
       [_findBucketIndex](bucket, key) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let cell = dart.as(bucket[i], LinkedHashMapCell);
           if (this[_equals](dart.as(cell[_key], K), dart.as(key, K)))
             return i;
         }
         return -1;
       }
     }
@@ skipping 22 matching lines @@
       }
       get iterator() {
         return new LinkedHashMapKeyIterator(this[_map], dart.as(dart.dload(this[_map], '_modifications'), core.int));
       }
       contains(element) {
         return dart.as(dart.dinvoke(this[_map], 'containsKey', element), core.bool);
       }
       forEach(f) {
         let cell = dart.as(dart.dload(this[_map], '_first'), LinkedHashMapCell);
         let modifications = dart.as(dart.dload(this[_map], '_modifications'), core.int);
-        while (cell !== null) {
+        while (cell != null) {
           f(dart.as(cell[_key], E));
-          if (modifications !== dart.dload(this[_map], '_modifications')) {
+          if (!dart.equals(modifications, dart.dload(this[_map], '_modifications'))) {
             throw new core.ConcurrentModificationError(this[_map]);
           }
           cell = cell[_next];
         }
       }
     }
     return LinkedHashMapKeyIterable;
   });
   let LinkedHashMapKeyIterable = LinkedHashMapKeyIterable$(dart.dynamic);
   let _cell = Symbol('_cell');
   let LinkedHashMapKeyIterator$ = dart.generic(function(E) {
     class LinkedHashMapKeyIterator extends core.Object {
       LinkedHashMapKeyIterator(map$, modifications$) {
         this[_map] = map$;
         this[_modifications] = modifications$;
         this[_cell] = null;
         this[_current] = null;
         this[_cell] = dart.as(dart.dload(this[_map], '_first'), LinkedHashMapCell);
       }
       get current() {
         return this[_current];
       }
       moveNext() {
-        if (this[_modifications] !== dart.dload(this[_map], '_modifications')) {
+        if (!dart.equals(this[_modifications], dart.dload(this[_map], '_modifications'))) {
           throw new core.ConcurrentModificationError(this[_map]);
-        } else if (this[_cell] === null) {
+        } else if (this[_cell] == null) {
           this[_current] = null;
           return false;
         } else {
           this[_current] = dart.as(this[_cell][_key], E);
           this[_cell] = this[_cell][_next];
           return true;
         }
       }
     }
     return LinkedHashMapKeyIterator;
@@ skipping 18 matching lines @@
       [_newSet]() {
         return new _HashSet();
       }
       get iterator() {
         return new HashSetIterator(this, this[_computeElements]());
       }
       get length() {
         return this[_length];
       }
       get isEmpty() {
-        return this[_length] === 0;
+        return this[_length] == 0;
       }
       get isNotEmpty() {
         return !dart.notNull(this.isEmpty);
       }
       contains(object) {
         if (_HashSet[_isStringElement](object)) {
           let strings = this[_strings];
-          return strings === null ? false : _HashSet[_hasTableEntry](strings, object);
+          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);
+          return nums == null ? false : _HashSet[_hasTableEntry](nums, object);
         } else {
           return this[_contains](object);
         }
       }
       [_contains](object) {
         let rest = this[_rest];
-        if (rest === null)
+        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.contains(object) ? object : null, E);
         }
         return this[_lookup](object);
       }
       [_lookup](object) {
         let rest = this[_rest];
-        if (rest === null)
+        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.get(index), E);
       }
       add(element) {
         if (_HashSet[_isStringElement](element)) {
           let strings = this[_strings];
-          if (strings === null)
+          if (strings == null)
             this[_strings] = strings = _HashSet[_newHashTable]();
           return this[_addHashTableEntry](strings, element);
         } else if (_HashSet[_isNumericElement](element)) {
           let nums = this[_nums];
-          if (nums === null)
+          if (nums == null)
             this[_nums] = nums = _HashSet[_newHashTable]();
           return this[_addHashTableEntry](nums, element);
         } else {
           return this[_add](element);
         }
       }
       [_add](element) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           this[_rest] = rest = _HashSet[_newHashTable]();
         let hash = this[_computeHashCode](element);
         let bucket = rest[hash];
-        if (bucket === null) {
+        if (bucket == null) {
           _HashSet[_setTableEntry](rest, hash, [element]);
         } else {
           let index = this[_findBucketIndex](bucket, element);
           if (dart.notNull(index) >= 0)
             return false;
           bucket.push(element);
         }
         this[_length] = dart.notNull(this[_length]) + 1;
         this[_elements] = null;
         return true;
       }
       addAll(objects) {
         for (let each of objects) {
           this.add(each);
         }
       }
       remove(object) {
         if (_HashSet[_isStringElement](object)) {
           return this[_removeHashTableEntry](this[_strings], object);
         } else if (_HashSet[_isNumericElement](object)) {
           return this[_removeHashTableEntry](this[_nums], object);
         } else {
           return this[_remove](object);
         }
       }
       [_remove](object) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           return false;
         let bucket = this[_getBucket](rest, object);
         let index = this[_findBucketIndex](bucket, object);
         if (dart.notNull(index) < 0)
           return false;
         this[_length] = dart.notNull(this[_length]) - 1;
         this[_elements] = null;
         bucket.splice(index, 1);
         return true;
       }
       clear() {
         if (dart.notNull(this[_length]) > 0) {
           this[_strings] = this[_nums] = this[_rest] = this[_elements] = null;
           this[_length] = 0;
         }
       }
       [_computeElements]() {
-        if (this[_elements] !== null)
+        if (this[_elements] != null)
           return this[_elements];
         let result = new core.List(this[_length]);
         let index = 0;
         let strings = this[_strings];
-        if (strings !== null) {
+        if (strings != null) {
           let names = Object.getOwnPropertyNames(strings);
           let entries = names.length;
           for (let i = 0; dart.notNull(i) < dart.notNull(entries); i = dart.notNull(i) + 1) {
             let element = names[i];
             result[index] = element;
             index = dart.notNull(index) + 1;
           }
         }
         let nums = this[_nums];
-        if (nums !== null) {
+        if (nums != null) {
           let names = Object.getOwnPropertyNames(nums);
           let entries = names.length;
           for (let i = 0; dart.notNull(i) < dart.notNull(entries); i = dart.notNull(i) + 1) {
             let element = +names[i];
             result[index] = element;
             index = dart.notNull(index) + 1;
           }
         }
         let rest = this[_rest];
-        if (rest !== null) {
+        if (rest != null) {
           let names = Object.getOwnPropertyNames(rest);
           let entries = names.length;
           for (let i = 0; dart.notNull(i) < dart.notNull(entries); i = dart.notNull(i) + 1) {
             let entry = names[i];
             let bucket = rest[entry];
             let length = bucket.length;
             for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
               result[index] = bucket[i];
               index = dart.notNull(index) + 1;
             }
           }
         }
-        dart.assert(index === this[_length]);
+        dart.assert(index == this[_length]);
         return this[_elements] = result;
       }
       [_addHashTableEntry](table, element) {
         if (_HashSet[_hasTableEntry](table, element))
           return false;
         _HashSet[_setTableEntry](table, element, 0);
         this[_length] = dart.notNull(this[_length]) + 1;
         this[_elements] = null;
         return true;
       }
       [_removeHashTableEntry](table, element) {
-        if (dart.notNull(table !== null) && dart.notNull(_HashSet[_hasTableEntry](table, element))) {
+        if (dart.notNull(table != null) && dart.notNull(_HashSet[_hasTableEntry](table, element))) {
           _HashSet[_deleteTableEntry](table, element);
           this[_length] = dart.notNull(this[_length]) - 1;
           this[_elements] = null;
           return true;
         } else {
           return false;
         }
       }
       static [_isStringElement](element) {
         return dart.notNull(typeof element == 'string') && dart.notNull(!dart.equals(element, '__proto__'));
       }
       static [_isNumericElement](element) {
         return dart.notNull(dart.is(element, core.num)) && (element & 0x3ffffff) === element;
       }
       [_computeHashCode](element) {
         return dart.dload(element, 'hashCode') & 0x3ffffff;
       }
       static [_hasTableEntry](table, key) {
         let entry = table[key];
-        return entry !== null;
+        return entry != null;
       }
       static [_setTableEntry](table, key, value) {
-        dart.assert(value !== null);
+        dart.assert(value != null);
         table[key] = value;
       }
       static [_deleteTableEntry](table, key) {
         delete table[key];
       }
       [_getBucket](table, element) {
         let hash = this[_computeHashCode](element);
         return dart.as(table[hash], core.List);
       }
       [_findBucketIndex](bucket, element) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           if (dart.equals(bucket[i], element))
             return i;
         }
         return -1;
       }
       static [_newHashTable]() {
         let table = Object.create(null);
         let temporaryKey = '<non-identifier-key>';
         _HashSet[_setTableEntry](table, temporaryKey, table);
         _HashSet[_deleteTableEntry](table, temporaryKey);
         return table;
       }
     }
     return _HashSet;
   });
   let _HashSet = _HashSet$(dart.dynamic);
   let _IdentityHashSet$ = dart.generic(function(E) {
     class _IdentityHashSet extends _HashSet$(E) {
       [_newSet]() {
         return new _IdentityHashSet();
       }
       [_computeHashCode](key) {
         return core.identityHashCode(key) & 0x3ffffff;
       }
       [_findBucketIndex](bucket, element) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           if (core.identical(bucket[i], element))
             return i;
         }
         return -1;
       }
     }
     return _IdentityHashSet;
   });
   let _IdentityHashSet = _IdentityHashSet$(dart.dynamic);
   let _equality = Symbol('_equality');
   let _hasher = Symbol('_hasher');
   let _CustomHashSet$ = dart.generic(function(E) {
     class _CustomHashSet extends _HashSet$(E) {
       _CustomHashSet(equality, hasher, validKey) {
         this[_equality] = equality;
         this[_hasher] = hasher;
-        this[_validKey] = dart.as(validKey !== null ? validKey : (x) => dart.is(x, E), _Predicate);
+        this[_validKey] = dart.as(validKey != null ? validKey : (x) => dart.is(x, E), _Predicate);
         super._HashSet();
       }
       [_newSet]() {
         return new _CustomHashSet(this[_equality], this[_hasher], this[_validKey]);
       }
       [_findBucketIndex](bucket, element) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           if (this[_equality](dart.as(bucket[i], E), dart.as(element, E)))
             return i;
         }
         return -1;
       }
       [_computeHashCode](element) {
         return this[_hasher](dart.as(element, E)) & 0x3ffffff;
@@ skipping 68 matching lines @@
       [_unsupported](operation) {
         throw `LinkedHashSet: unsupported ${operation}`;
       }
       get iterator() {
         return dart.as(new LinkedHashSetIterator(this, this[_modifications]), core.Iterator$(E));
       }
       get length() {
         return this[_length];
       }
       get isEmpty() {
-        return this[_length] === 0;
+        return this[_length] == 0;
       }
       get isNotEmpty() {
         return !dart.notNull(this.isEmpty);
       }
       contains(object) {
         if (_LinkedHashSet[_isStringElement](object)) {
           let strings = this[_strings];
-          if (strings === null)
+          if (strings == null)
             return false;
           let cell = dart.as(_LinkedHashSet[_getTableEntry](strings, object), LinkedHashSetCell);
-          return cell !== null;
+          return cell != null;
         } else if (_LinkedHashSet[_isNumericElement](object)) {
           let nums = this[_nums];
-          if (nums === null)
+          if (nums == null)
             return false;
           let cell = dart.as(_LinkedHashSet[_getTableEntry](nums, object), LinkedHashSetCell);
-          return cell !== null;
+          return cell != null;
         } else {
           return this[_contains](object);
         }
       }
       [_contains](object) {
         let rest = this[_rest];
-        if (rest === null)
+        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.contains(object) ? object : null, E);
         } else {
           return this[_lookup](object);
         }
       }
       [_lookup](object) {
         let rest = this[_rest];
-        if (rest === null)
+        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.get(index), '_element'), E);
       }
       forEach(action) {
         let cell = this[_first];
         let modifications = this[_modifications];
-        while (cell !== null) {
+        while (cell != null) {
           action(dart.as(cell[_element], E));
-          if (modifications !== this[_modifications]) {
+          if (modifications != this[_modifications]) {
             throw new core.ConcurrentModificationError(this);
           }
           cell = cell[_next];
         }
       }
       get first() {
-        if (this[_first] === null)
+        if (this[_first] == null)
           throw new core.StateError("No elements");
         return dart.as(this[_first][_element], E);
       }
       get last() {
-        if (this[_last] === null)
+        if (this[_last] == null)
           throw new core.StateError("No elements");
         return dart.as(this[_last][_element], E);
       }
       add(element) {
         if (_LinkedHashSet[_isStringElement](element)) {
           let strings = this[_strings];
-          if (strings === null)
+          if (strings == null)
             this[_strings] = strings = _LinkedHashSet[_newHashTable]();
           return this[_addHashTableEntry](strings, element);
         } else if (_LinkedHashSet[_isNumericElement](element)) {
           let nums = this[_nums];
-          if (nums === null)
+          if (nums == null)
             this[_nums] = nums = _LinkedHashSet[_newHashTable]();
           return this[_addHashTableEntry](nums, element);
         } else {
           return this[_add](element);
         }
       }
       [_add](element) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           this[_rest] = rest = _LinkedHashSet[_newHashTable]();
         let hash = this[_computeHashCode](element);
         let bucket = rest[hash];
-        if (bucket === null) {
+        if (bucket == null) {
           let cell = this[_newLinkedCell](element);
           _LinkedHashSet[_setTableEntry](rest, hash, [cell]);
         } else {
           let index = this[_findBucketIndex](bucket, element);
           if (dart.notNull(index) >= 0)
             return false;
           let cell = this[_newLinkedCell](element);
           bucket.push(cell);
         }
         return true;
       }
       remove(object) {
         if (_LinkedHashSet[_isStringElement](object)) {
           return this[_removeHashTableEntry](this[_strings], object);
         } else if (_LinkedHashSet[_isNumericElement](object)) {
           return this[_removeHashTableEntry](this[_nums], object);
         } else {
           return this[_remove](object);
         }
       }
       [_remove](object) {
         let rest = this[_rest];
-        if (rest === null)
+        if (rest == null)
           return false;
         let bucket = this[_getBucket](rest, object);
         let index = this[_findBucketIndex](bucket, object);
         if (dart.notNull(index) < 0)
           return false;
         let cell = dart.as(bucket.splice(index, 1)[0], LinkedHashSetCell);
         this[_unlinkCell](cell);
         return true;
       }
       removeWhere(test) {
         this[_filterWhere](test, true);
       }
       retainWhere(test) {
         this[_filterWhere](test, false);
       }
       [_filterWhere](test, removeMatching) {
         let cell = this[_first];
-        while (cell !== null) {
+        while (cell != null) {
           let element = dart.as(cell[_element], E);
           let next = cell[_next];
           let modifications = this[_modifications];
-          let shouldRemove = removeMatching === test(element);
-          if (modifications !== this[_modifications]) {
+          let shouldRemove = removeMatching == test(element);
+          if (modifications != this[_modifications]) {
             throw new core.ConcurrentModificationError(this);
           }
           if (shouldRemove)
             this.remove(element);
           cell = next;
         }
       }
       clear() {
         if (dart.notNull(this[_length]) > 0) {
           this[_strings] = this[_nums] = this[_rest] = this[_first] = this[_last] = null;
           this[_length] = 0;
           this[_modified]();
         }
       }
       [_addHashTableEntry](table, element) {
         let cell = dart.as(_LinkedHashSet[_getTableEntry](table, element), LinkedHashSetCell);
-        if (cell !== null)
+        if (cell != null)
           return false;
         _LinkedHashSet[_setTableEntry](table, element, this[_newLinkedCell](element));
         return true;
       }
       [_removeHashTableEntry](table, element) {
-        if (table === null)
+        if (table == null)
           return false;
         let cell = dart.as(_LinkedHashSet[_getTableEntry](table, element), LinkedHashSetCell);
-        if (cell === null)
+        if (cell == null)
           return false;
         this[_unlinkCell](cell);
         _LinkedHashSet[_deleteTableEntry](table, element);
         return true;
       }
       [_modified]() {
         this[_modifications] = dart.notNull(this[_modifications]) + 1 & 67108863;
       }
       [_newLinkedCell](element) {
         let cell = new LinkedHashSetCell(element);
-        if (this[_first] === null) {
+        if (this[_first] == null) {
           this[_first] = this[_last] = cell;
         } else {
           let last = this[_last];
           cell[_previous] = last;
           this[_last] = last[_next] = cell;
         }
         this[_length] = dart.notNull(this[_length]) + 1;
         this[_modified]();
         return cell;
       }
       [_unlinkCell](cell) {
         let previous = cell[_previous];
         let next = cell[_next];
-        if (previous === null) {
+        if (previous == null) {
           dart.assert(dart.equals(cell, this[_first]));
           this[_first] = next;
         } else {
           previous[_next] = next;
         }
-        if (next === null) {
+        if (next == null) {
           dart.assert(dart.equals(cell, this[_last]));
           this[_last] = previous;
         } else {
           next[_previous] = previous;
         }
         this[_length] = dart.notNull(this[_length]) - 1;
         this[_modified]();
       }
       static [_isStringElement](element) {
         return dart.notNull(typeof element == 'string') && dart.notNull(!dart.equals(element, '__proto__'));
       }
       static [_isNumericElement](element) {
         return dart.notNull(dart.is(element, core.num)) && (element & 0x3ffffff) === element;
       }
       [_computeHashCode](element) {
         return dart.dload(element, 'hashCode') & 0x3ffffff;
       }
       static [_getTableEntry](table, key) {
         return table[key];
       }
       static [_setTableEntry](table, key, value) {
-        dart.assert(value !== null);
+        dart.assert(value != null);
         table[key] = value;
       }
       static [_deleteTableEntry](table, key) {
         delete table[key];
       }
       [_getBucket](table, element) {
         let hash = this[_computeHashCode](element);
         return dart.as(table[hash], core.List);
       }
       [_findBucketIndex](bucket, element) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let cell = dart.as(bucket[i], LinkedHashSetCell);
           if (dart.equals(cell[_element], element))
             return i;
         }
         return -1;
       }
       static [_newHashTable]() {
         let table = Object.create(null);
         let temporaryKey = '<non-identifier-key>';
         _LinkedHashSet[_setTableEntry](table, temporaryKey, table);
         _LinkedHashSet[_deleteTableEntry](table, temporaryKey);
         return table;
       }
     }
     return _LinkedHashSet;
   });
   let _LinkedHashSet = _LinkedHashSet$(dart.dynamic);
   let _LinkedIdentityHashSet$ = dart.generic(function(E) {
     class _LinkedIdentityHashSet extends _LinkedHashSet$(E) {
       [_newSet]() {
         return new _LinkedIdentityHashSet();
       }
       [_computeHashCode](key) {
         return core.identityHashCode(key) & 0x3ffffff;
       }
       [_findBucketIndex](bucket, element) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let cell = dart.as(bucket[i], LinkedHashSetCell);
           if (core.identical(cell[_element], element))
             return i;
         }
         return -1;
       }
     }
     return _LinkedIdentityHashSet;
   });
   let _LinkedIdentityHashSet = _LinkedIdentityHashSet$(dart.dynamic);
   let _LinkedCustomHashSet$ = dart.generic(function(E) {
     class _LinkedCustomHashSet extends _LinkedHashSet$(E) {
       _LinkedCustomHashSet(equality, hasher, validKey) {
         this[_equality] = equality;
         this[_hasher] = hasher;
-        this[_validKey] = dart.as(validKey !== null ? validKey : (x) => dart.is(x, E), _Predicate);
+        this[_validKey] = dart.as(validKey != null ? validKey : (x) => dart.is(x, E), _Predicate);
         super._LinkedHashSet();
       }
       [_newSet]() {
         return new _LinkedCustomHashSet(this[_equality], this[_hasher], this[_validKey]);
       }
       [_findBucketIndex](bucket, element) {
-        if (bucket === null)
+        if (bucket == null)
           return -1;
         let length = bucket.length;
         for (let i = 0; dart.notNull(i) < dart.notNull(length); i = dart.notNull(i) + 1) {
           let cell = dart.as(bucket[i], LinkedHashSetCell);
           if (this[_equality](dart.as(cell[_element], E), dart.as(element, E)))
             return i;
         }
         return -1;
       }
       [_computeHashCode](element) {
@@ skipping 48 matching lines @@
         this[_set] = set$;
         this[_modifications] = modifications$;
         this[_cell] = null;
         this[_current] = null;
         this[_cell] = dart.as(dart.dload(this[_set], '_first'), LinkedHashSetCell);
       }
       get current() {
         return this[_current];
       }
       moveNext() {
-        if (this[_modifications] !== dart.dload(this[_set], '_modifications')) {
+        if (!dart.equals(this[_modifications], dart.dload(this[_set], '_modifications'))) {
           throw new core.ConcurrentModificationError(this[_set]);
-        } else if (this[_cell] === null) {
+        } else if (this[_cell] == null) {
           this[_current] = null;
           return false;
         } else {
           this[_current] = dart.as(this[_cell][_element], E);
           this[_cell] = this[_cell][_next];
           return true;
         }
       }
     }
     return LinkedHashSetIterator;
@@ skipping 57 matching lines @@
   exports.LinkedHashMapKeyIterable = LinkedHashMapKeyIterable;
   exports.LinkedHashMapKeyIterable$ = LinkedHashMapKeyIterable$;
   exports.LinkedHashMapKeyIterator = LinkedHashMapKeyIterator;
   exports.LinkedHashMapKeyIterator$ = LinkedHashMapKeyIterator$;
   exports.HashSetIterator = HashSetIterator;
   exports.HashSetIterator$ = HashSetIterator$;
   exports.LinkedHashSetCell = LinkedHashSetCell;
   exports.LinkedHashSetIterator = LinkedHashSetIterator;
   exports.LinkedHashSetIterator$ = LinkedHashSetIterator$;
 })(collection || (collection = {}));