(Message re-sent)
Hi everyone. I'm not so skillful with GADTs and DataKinds, so I assume this mailing list is appropriate to post on.

Basically, I wanted to do GADT like this (involving GHC.TypeNats):
data Symmetric (n :: Nat) where
    S1 :: Symmetric 1
    (:.) :: (KnownNat n, 2 <= n) => Cyclic n -> Symmetric (n-1) -> Symmetric n
But I had some issues with this. The full question is here (on Stack Overflow):

https://stackoverflow.com/q/54000646/4540658

Sincerely,
Dannyu NDos