canReturnSame property

Whether the mapper can return the same instance it was given.

This can be used to optimize a mapper.

Example

class Example {
  static const kind = ImmutableKind<Example>(
    name: 'Example',
    blank: Example(),
    walk: _walk,
  );
  static Example _walk(Mapper f, Example t) {
    // Map all fields:
    final someField = f(t.someField, 'someField');

    // Optimization: Check whether we can return the same instance.
    if (f.canReturnSame) {
      return t;
    }
    return Example(someField: someField);
  }

  final String someField;

  const Example({this.someField});
}