covariant method

@override bool covariant(dynamic x)

Assert that JavaScript's x is the proper type represented by this Type.

Implementation

@override
bool covariant(x) {
  // Ignoring types other than `Map`.
  if (x is! Map) {
    return true;
  }
  return (x).entries.length == 1 &&
      _fields.every((entry) {
        // [k, v]
        return !x.containsKey(entry.key) ||
            entry.value.covariant(x[entry.key]);
      });
}