I think something problematic is happening with type inference here,
and better types could be picked. Right now, Typed Racket is doing
this:
(compose (λ (x) x) (inst (λ #:forall (a) ({x : a}) x) Nothing))
when it should probably do
(compose (λ (x) x) (inst (λ #:forall (a) ({x : a}) x) Any))
However, using polymorphic arguments (such as your second function)
to polymorphic functions (such as `compose`) in general won't produce
the results you want, and I recommend writing the instantiation you
want explicitly.
Sam
On Tue, Sep 29, 2015 at 2:33 PM, Matthias Felleisen
<[email protected]> wrote:
>
> Why does this
>
>> (compose (λ (x) x) (λ #:forall (a) ({x : a}) x))
>
> have this type:
>
>> - : (-> Nothing Any)
>
> Thanks -- Matthias
>
>
>
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