[racket] Typed Racket vs. Haskell

> It's also possible to write Typed Racket programs "types first", like
> one would in Haskell, and I sometimes do. The "sums-of-products"
> programming style of Haskell and ML can be expressed easily with Typed
> Racket's structs and union types. You can also mix and match between
> "Haskell" and "Racket" styles of programming, and it will all work.

Are you talking about this?

We have already seen the : type annotation form. This is useful for
definitions, at both the top level of a module

(: x Number)
(define x 7)

and in an internal definition

(let ()
  (: x Number)
  (define x 7)
  (add1 x))

http://docs.racket-lang.org/ts-guide/more.html#(part._.Annotating_.Definitions)

> You can even take this "mix and match" approach even further, and mix
> typed and untyped code. Typed Racket modules can interact with untyped
> Racket modules and contract checks at the boundary will prevent untyped
> code from breaking the typed code. This is very handy, and is probably
> the Typed Racket feature I find myself missing the most when programming
> in Haskell or ML.

Very interesting.
I'm going to write a library. I want it to be available for the largest
number of people.
Can other Lisp-like languages (e.g. Guile) use libraries written in Typed
Racket?

> Of course, Haskell also provides type system features that Typed Racket
> does not, such as type classes or type-level programming.

Is there a need for such features in Typed Racket?
Is it possible to implement them?
Is there a plan to implement them?