Why is this-command-keys missing?

[Lennart Borgman]

compilation-mode binds

    (define-key map "\t" 'compilation-next-error)

You can use TAB to go to next error because of this.

However if you hit TAB then this-command-keys will contain (something
similar to) TAB and not "\t". So you can't do

   (key-binding (this-command-keys) t)

to get back the binding that is really active, i.e. compilation-next-error.


What are you supposed to do in a case like this to get back the key
binding compilation-next-error?