anchor.diff:  
   @notNull
   bool _isTop(type) {
  -  if (_isNullable(type)) return JS('!', '# === #', type.type, Object);
  +  if (_isNullable(type)) return JS('!', '#.type === #', type, Object);
   
     return JS('!', '# === # || # === #', type, dynamic, type, void_);
   }
  
positive.code:     bool hasFreeFormal(t) {
        // Ignore nullability wrappers.
        if (_isLegacy(t) || _isNullable(t)) {
          return hasFreeFormal(JS<Type>('', '#.type', t));
        }
        if (partials.containsKey(t)) return true;
        // Generic classes and typedefs.
  
negative.code:   var result = isNormalized
        ? _Type(type)
        : (_isLegacy(type)
            ? wrapType(JS<Object>('!', '#.type', type))
            : _canonicalizeNormalizedTypeObject(type));
    JS('', '#[#] = #', type, _typeObject, result);
    return result;
  