class ValueObjAt is ObjAt { }

A subclass of ObjAt that should be used to indicate that a class produces objects that are value types - in other words, that are immutable after they have been initialized.

my %h = a => 42;   # mutable Hash
dd %h.WHICH;       # OUTPUT: «ObjAt.new("Hash|1402...888")␤»

my $date = Date.new(2025,7,20); # immutable Date
say $date.WHICH;                # OUTPUT: «ValueObjAt.new("Date|60876")␤»

If you create a class that should be considered a value type, you should add a WHICH method to that class that returns a ValueObjAt object, for instance:

class YourClass {
    has $.foo;  # note these are not mutable
    has $.bar;

    method WHICH() {
        ValueObjAt.new("YourClass|$!foo|$!bar");
    }
}

Note that it is customary to always start the identifying string with the name of the object, followed by a "|". This to prevent confusion with other classes that may generate similar string values: the name of the class should then be enough of a differentiator to prevent collisions.

Typegraph§