anchor.diff:  // Environment variables are case-insensitive on Windows. In order
   // to reflect that we use a case-insensitive string map on Windows.
   class _CaseInsensitiveStringMap<V> implements Map<String, V> {
  -  Map<String, V> _map;
  -
  -  _CaseInsensitiveStringMap() : _map = new Map<String, V>();
  -
  -  _CaseInsensitiveStringMap.from(Map<String, V> other)
  -      : _map = new Map<String, V>() {
  -    other.forEach((String key, V value) {
  -      _map[key.toUpperCase()] = value;
  -    });
  -  }
  +  final Map<String, V> _map = new Map<String, V>();
   
     bool containsKey(String key) => _map.containsKey(key.toUpperCase());
     bool containsValue(Object value) => _map.containsValue(value);
  
positive.code:   int get length => _map.length;
    bool get isEmpty => _map.isEmpty;
    bool get isNotEmpty => _map.isNotEmpty;
  }
  
negative.code:           result[str.substring(0, equalsIndex)] =
                str.substring(equalsIndex + 1);
          }
          _environmentCache = new UnmodifiableMapView<String, String>(result);
        } else {
          _environmentCache = env;
        }
  