anchor.diff:    var result = isNormalized
         ? _Type(type)
         : (_isLegacy(type)
  -          ? wrapType(type.type)
  +          ? wrapType(JS<Object>('!', '#.type', type))
             : _canonicalizeNormalizedTypeObject(type));
     JS('', '#[#] = #', type, _typeObject, result);
     return result;
  
positive.code: Object _computeNullable(type) {
    // *? normalizes to ?.
    if (_isLegacy(type)) {
      return nullable(JS<Object>('', '#.type', type));
    }
    if (_isNullable(type) ||
        _isTop(type) ||
  
negative.code: 
  @notNull
  bool _isTop(type) {
    if (_isNullable(type)) return JS('!', '#.type === #', type, Object);
  
    return JS('!', '# === # || # === #', type, dynamic, type, void_);
  }
  