[Haskell-cafe] Splicing type signature in TH

[John Lato]

You can create a new forall'd type variable.  Would that work?

On Thu, Oct 16, 2014 at 12:06 PM, Hugo Pacheco <hpacheco at gmail.com> wrote:

> Hi list,
>
> I am 99.9% sure that this is currently not possible, but I might as well
> ask:
>
>    - Is there a way to lift type variables into Template Haskell type
>    splices?
>
> What I had in mind would be something like this (erroneous) code:
>
> liftT :: a -> Q Type
> liftT (_::a) = [t| $a |]
>
> I have no idea how hard it would be to implement such a feature, or if it
> is remotely doable.
> Naively, it seems to me that TH would have to delay evaluating the splice
> until the type variable is fully expanded, but all the necessary
> information would still be available at some point during compilation.
>
> Cheers,
> hugo
>
> --
> www.cs.cornell.edu/~hpacheco
>
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