Source

bool get isDeprecated {
  // If element.metadata is empty, it might be because this is a property
  // where the metadata belongs to the individual getter/setter
  if (element.metadata.isEmpty && element is PropertyInducingElement) {
    var pie = element as PropertyInducingElement;

    // The getter or the setter might be null – so the stored value may be
    // `true`, `false`, or `null`
    var getterDeprecated = pie.getter?.metadata?.any((a) => a.isDeprecated);
    var setterDeprecated = pie.setter?.metadata?.any((a) => a.isDeprecated);

    var deprecatedValues =
        [getterDeprecated, setterDeprecated].where((a) => a != null).toList();

    // At least one of these should be non-null. Otherwise things are weird
    assert(deprecatedValues.isNotEmpty);

    // If there are both a setter and getter, only show the property as
    // deprecated if both are deprecated.
    return deprecatedValues.every((d) => d);
  }
  return element.metadata.any((a) => a.isDeprecated);
}