immutable top-level constant
Used to annotate a class
C. Indicates that
C and all subtypes of
must be immutable.
A class is immutable if all of the instance fields of the class, whether
defined directly or inherited, are
Tools, such as the analyzer, can provide feedback if the annotation is associated with anything other than a class, or a class that has this annotation or extends, implements or mixes in a class that has this annotation is not immutable.
const Immutable immutable = const Immutable()