I think I also replied already in github, but for the record:

On Mon, Feb 17, 2020 at 8:52 PM Tristan Cacqueray <tdecacqu@redhat.com> wrote:
On Mon, Feb 17, 2020 at 18:16 Jens-Ulrik Petersen wrote:
> Or what did you mean by devel files exactly?

I meant the files that enable using the haskell dhall binding[0].
I guess this would be named ghc-dhall-devel

Okay, the problem is the way the copr is built currently using cabal-install makes this quite difficult.

If you need it locally for something I would suggest just to cabal install it yourself, or via stack.

Anyway hopefully dhall will land in Fedora before too long.

Jens