In a class definition like this:

class D < C
end

there might be a const_added hook, and also an inherited hook being triggered when D is just created.

Those are user-level hooks, and the following is observable:

1. When they are invoked, the class object stored in D has been created and it has the expected superclass.
2. When they are invoked, the constant has been created and constant-related state reflects that.

The specs proposed in this patch specify this contract.

(What I described above is the consensus achieved in discussions in https://bugs.ruby-lang.org/issues/21143, https://bugs.ruby-lang.org/issues/21193, and related PRs.)

/cc @byroot @eregon