Re: [Haskell-cafe] Repeating type variables in MultiParamTypeClasses instance heads

On Thu, 6 May 2021, Leif-Erik Krüger wrote:

So, is there a good reason for the design choice of allowing these kinds of overlap without FlexibleInstances? Am I missing something here?

I am surprised. I just tried it with different GHC versions, all of them accept those overlapping instances without enabling FlexibleInstances. {-# LANGUAGE MultiParamTypeClasses #-} module FlexibleInstance where class C a b c where instance C [a] [a] [b] where instance C [a] [b] [b] where