fixes #52, fields shadowing getters/setters or other fields

lib/runtime/dart/_internal.js

 var _internal;
 (function(exports) {
   'use strict';
   class EfficientLength extends core.Object {}
   let ListIterable$ = dart.generic(function(E) {
     class ListIterable extends collection.IterableBase$(E) {
       ListIterable() {
         super.IterableBase();
       }
       get [core.$iterator]() {
@@ skipping 302 matching lines @@
     }
     return SubListIterable;
   });
   let SubListIterable = SubListIterable$();
   let _length = dart.JsSymbol('_length');
   let _index = dart.JsSymbol('_index');
   let _current = dart.JsSymbol('_current');
   let ListIterator$ = dart.generic(function(E) {
     class ListIterator extends core.Object {
       ListIterator(iterable) {
-        this[_iterable] = iterable;
-        this[_length] = iterable[core.$length];
-        this[_index] = 0;
-        this[_current] = null;
+        dart.initField(ListIterator, this, _iterable, iterable);
+        dart.initField(ListIterator, this, _length, iterable[core.$length]);
+        dart.initField(ListIterator, this, _index, 0);
+        dart.initField(ListIterator, this, _current, null);
       }
       get current() {
         return this[_current];
       }
       moveNext() {
         let length = this[_iterable][core.$length];
         if (this[_length] != length) {
           throw new core.ConcurrentModificationError(this[_iterable]);
         }
         if (dart.notNull(this[_index]) >= dart.notNull(length)) {
@@ skipping 166 matching lines @@
       }
     }
     return ExpandIterable;
   });
   let ExpandIterable = ExpandIterable$();
   let _currentExpansion = dart.JsSymbol('_currentExpansion');
   let _nextExpansion = dart.JsSymbol('_nextExpansion');
   let ExpandIterator$ = dart.generic(function(S, T) {
     class ExpandIterator extends core.Object {
       ExpandIterator(iterator, f) {
-        this[_iterator] = iterator;
-        this[_f] = f;
-        this[_currentExpansion] = dart.as(new EmptyIterator(), core.Iterator$(T));
-        this[_current] = null;
+        dart.initField(ExpandIterator, this, _iterator, iterator);
+        dart.initField(ExpandIterator, this, _f, f);
+        dart.initField(ExpandIterator, this, _currentExpansion, dart.as(new EmptyIterator(), core.Iterator$(T)));
+        dart.initField(ExpandIterator, this, _current, null);
       }
       [_nextExpansion]() {}
       get current() {
         return this[_current];
       }
       moveNext() {
         if (this[_currentExpansion] == null)
           return false;
         while (!dart.notNull(this[_currentExpansion].moveNext())) {
           this[_current] = null;
@@ skipping 862 matching lines @@
     }
     [core.$elementAt](index) {
       core.RangeError.checkValidIndex(index, this);
       return index;
     }
   }
   let _values = dart.JsSymbol('_values');
   let ListMapView$ = dart.generic(function(E) {
     class ListMapView extends core.Object {
       ListMapView(values) {
-        this[_values] = values;
+        dart.initField(ListMapView, this, _values, values);
       }
       get(key) {
         return this.containsKey(key) ? this[_values][core.$get](key) : null;
       }
       get length() {
         return this[_values][core.$length];
       }
       get values() {
         return new (SubListIterable$(E))(this[_values], 0, null);
       }
@@ skipping 420 matching lines @@
         Sort[_doSort](a, less, great, compare);
       } else {
         Sort[_doSort](a, less, great, compare);
       }
     }
   }
   Sort._INSERTION_SORT_THRESHOLD = 32;
   let _name = dart.JsSymbol('_name');
   class Symbol extends core.Object {
     Symbol(name) {
-      this[_name] = name;
+      dart.initField(Symbol, this, _name, name);
     }
     unvalidated(name) {
-      this[_name] = name;
+      dart.initField(Symbol, this, _name, name);
     }
     validated(name) {
-      this[_name] = Symbol.validatePublicSymbol(name);
+      dart.initField(Symbol, this, _name, Symbol.validatePublicSymbol(name));
     }
     ['=='](other) {
       return dart.is(other, Symbol) && dart.equals(this[_name], dart.dload(other, _name));
     }
     get hashCode() {
       let arbitraryPrime = 664597;
       return 536870911 & dart.notNull(arbitraryPrime) * dart.notNull(this[_name].hashCode);
     }
     toString() {
       return `Symbol("${this[_name]}")`;
@@ skipping 96 matching lines @@
   exports.ReversedListIterable = ReversedListIterable;
   exports.UnmodifiableListError = UnmodifiableListError;
   exports.NonGrowableListError = NonGrowableListError;
   exports.makeListFixedLength = makeListFixedLength;
   exports.Lists = Lists;
   exports.printToConsole = printToConsole;
   exports.Sort = Sort;
   exports.Symbol = Symbol;
   exports.POWERS_OF_TEN = POWERS_OF_TEN;
 })(_internal || (_internal = {}));