Hashcode et equals
Code:
Hashcode:
@override
int get hashCode => style.hashCode;
Equals:
@override
bool operator ==(Object other) {
  if (identical(this, other)) {
    return true;
  }
  if (other.runtimeType != runtimeType) {
    return false;
  }
  return other is FilledButtonThemeData && other.style == style;
}