Typed Racket extend gui classes

I want to extend the class horizontal-panel%but somehow I am getting this error message:

class has init `stretchable-height' that is not in expected type in: (class horizontal-panel% (super-new))

This is my code so far:

#lang typed/racket
(require typed/racket/gui)

(define-type Graph-Tab%
  (Class #:implements  Horizontal-Panel%

         ))
(: graph-tab% : Graph-Tab%)
(define graph-tab%
  (class horizontal-panel%
    (super-new)

    ))

As you can probably tell I am very new to racket and I am still learning.

Solution

I'm pretty sure what that error message means is that you need to "init" all of the things from that class.

One useful way to do this is to change from #:implements to #:implements/inits in your type definition and call init on the missing value(s) (in this case stretchable-height).

If you don't know exactly what those are, you can simply put (init-rest) and that should take care of it.

(here's the documentation for Initialization Variables and also for horizontal-panel%)