metalet with postfix improvement

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$(E) {
       UnmodifiableListView(source) {
         this[_source] = source;
         super.UnmodifiableListBase();
       }
@@ skipping 1487 matching lines @@
         return result;
       }
       [core.$toSet]() {
         let result = new (core.Set$(E))();
         for (let i = 0; dart.notNull(i) < dart.notNull(this.length); i = dart.notNull(i) + 1) {
           result.add(this[core.$get](i));
         }
         return result;
       }
       [core.$add](element) {
-        this[core.$set]((() => {
-          let o$ = this, x$ = o$[core.$length];
-          o$[core.$length] = dart.notNull(x$) + 1;
-          return x$;
-        }).bind(this)(), element);
+        this[core.$set](dart.prop(this, 'length').notNull++, element);
       }
       [core.$addAll](iterable) {
         for (let element of iterable) {
-          this[core.$set]((() => {
-            let o$ = this, x$ = o$[core.$length];
-            o$[core.$length] = dart.notNull(x$) + 1;
-            return x$;
-          }).bind(this)(), element);
+          this[core.$set](dart.prop(this, 'length').notNull++, element);
         }
       }
       [core.$remove](element) {
         for (let i = 0; dart.notNull(i) < dart.notNull(this[core.$length]); i = dart.notNull(i) + 1) {
           if (dart.equals(this[core.$get](i), element)) {
             this[core.$setRange](i, dart.notNull(this[core.$length]) - 1, this, dart.notNull(i) + 1);
             let o$ = this;
             o$[core.$length] = dart.notNull(o$[core.$length]) - 1;
             return true;
           }
@@ skipping 186 matching lines @@
         return -1;
       }
       [core.$insert](index, element) {
         core.RangeError.checkValueInInterval(index, 0, this.length, "index");
         if (index == this[core.$length]) {
           this.add(element);
           return;
         }
         if (!(typeof index == 'number'))
           throw new core.ArgumentError(index);
-        let o$ = this;
-        o$[core.$length] = dart.notNull(o$[core.$length]) + 1;
+        dart.prop(this, 'length').notNull++;
         this.setRange(dart.notNull(index) + 1, this[core.$length], this, index);
         this[core.$set](index, element);
       }
       [core.$removeAt](index) {
         let result = this[core.$get](index);
         this.setRange(index, dart.notNull(this[core.$length]) - 1, this, dart.notNull(index) + 1);
         this.length = dart.notNull(this.length) - 1;
         return result;
       }
       [core.$insertAll](index, iterable) {
@@ skipping 3220 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 = {}));