anchor.diff:          if (((Integer.nativeValue(from) > lastIndex) || (length <= 0)) || ((Integer.nativeValue(from) + length) <= 0)) {
               return $package$empty;
           } else if (Integer.nativeValue(from) < 0) {
  -            return new ArraySequence(array.measure(Integer.instance(0), length + Integer.nativeValue(from)));
  +            return new ArraySequence(_$array.measure(Integer.instance(0), length + Integer.nativeValue(from)));
           } else {
  -            return new ArraySequence(array.measure(from, length));
  +            return new ArraySequence(_$array.measure(from, length));
           }
       }
       Sequential span([Integer from, Integer to]) {
           if (Integer.nativeValue(from) <= Integer.nativeValue(to)) {
  -            return ((Sequential $lhs$) => $lhs$ == null ? new ArraySequence(array.span(from, to)) : $lhs$)((Integer.nativeValue(to) < 0) || (Integer.nativeValue(from) > lastIndex) ? $package$empty : null);
  +            return ((Sequential $lhs$) => $lhs$ == null ? new ArraySequence(_$array.span(from, to)) : $lhs$)((Integer.nativeValue(to) < 0) || (Integer.nativeValue(from) > lastIndex) ? $package$empty : null);
           } else {
  -            return ((Sequential $lhs$) => $lhs$ == null ? new ArraySequence(array.span(from, to)) : $lhs$)((Integer.nativeValue(from) < 0) || (Integer.nativeValue(to) > lastIndex) ? $package$empty : null);
  -        }
  -    }
  -    Sequential spanFrom([Integer from]) => ((Sequential $lhs$) => $lhs$ == null ? new ArraySequence(array.spanFrom(from)) : $lhs$)(Integer.nativeValue(from) > lastIndex ? $package$empty : null);
  -    Sequential spanTo([Integer to]) => ((Sequential $lhs$) => $lhs$ == null ? new ArraySequence(array.spanTo(to)) : $lhs$)(Integer.nativeValue(to) < 0 ? $package$empty : null);
  -    $dart$core.int firstOccurrence([$dart$core.Object element]) => array.firstOccurrence(element);
  -    $dart$core.int lastOccurrence([$dart$core.Object element]) => array.lastOccurrence(element);
  -    $dart$core.bool occurs([$dart$core.Object element]) => array.occurs(element);
  +            return ((Sequential $lhs$) => $lhs$ == null ? new ArraySequence(_$array.span(from, to)) : $lhs$)((Integer.nativeValue(from) < 0) || (Integer.nativeValue(to) > lastIndex) ? $package$empty : null);
  +        }
  +    }
  +    Sequential spanFrom([Integer from]) => ((Sequential $lhs$) => $lhs$ == null ? new ArraySequence(_$array.spanFrom(from)) : $lhs$)(Integer.nativeValue(from) > lastIndex ? $package$empty : null);
  +    Sequential spanTo([Integer to]) => ((Sequential $lhs$) => $lhs$ == null ? new ArraySequence(_$array.spanTo(to)) : $lhs$)(Integer.nativeValue(to) < 0 ? $package$empty : null);
  +    $dart$core.int firstOccurrence([$dart$core.Object element]) => _$array.firstOccurrence(element);
  +    $dart$core.int lastOccurrence([$dart$core.Object element]) => _$array.lastOccurrence(element);
  +    $dart$core.bool occurs([$dart$core.Object element]) => _$array.occurs(element);
       $dart$core.bool equals([$dart$core.Object that]) => List.$equals(this, that);
       $dart$core.int get hashCode => List.$get$hash(this);
       $dart$core.String toString() => Sequence.$get$string(this);
  
positive.code:     })();
      $dart$core.Object findLast([Callable selecting]) => find(selecting);
      Singleton sort([Callable comparing]) => this;
      $dart$core.bool any([Callable selecting]) => Boolean.nativeValue(selecting.f(element) as Boolean);
      $dart$core.bool every([Callable selecting]) => Boolean.nativeValue(selecting.f(element) as Boolean);
      $dart$core.Object skip([$dart$core.int skipping]) => (($dart$core.Object $lhs$) => $lhs$ == null ? $package$empty : $lhs$)(skipping < 1 ? this : null);
      $dart$core.Object take([$dart$core.int taking]) => (($dart$core.Object $lhs$) => $lhs$ == null ? $package$empty : $lhs$)(taking > 0 ? this : null);
      $dart$core.Object get coalesced => (() {
          $dart$core.bool doElse$6 = true;
          if (!(element == null)) {
              doElse$6 = false;
              return new Singleton(element);
          }
          if (doElse$6) {
              return $package$empty;
          }
      })();
      Iterable chain([Iterable other]) => other.follow(element);
      void each([Callable step]) => step.f(element);
      $dart$core.bool get empty => Sequence.$get$empty(this);
      Range get keys => Sequence.$get$keys(this);
      Range indexes() => Sequence.$indexes(this);
  
negative.code:         }
          $dart$core.String oldString = this.toString();
          clear();
          _$delegate.write(String.instance((String.nativeValue(String.instance(oldString).spanTo(Integer.instance(index - 1))) + string) + String.nativeValue(String.instance(oldString).spanFrom(Integer.instance(index)))));
          return this;
      }
      StringBuilder insertCharacter([$dart$core.int index, Character character]) => insert(index, character.toString());
  