Error message: (%,%) shows up when with accidental paren
I accidentally wrote an extra closing parens in instance declaration
$ ghci -ignore-dot-ghci -XRankNTypes
GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help
Prelude> class (Category (Src f), forall xx. xx => Eq xx)) => Functor f
<interactive>:1:8: error:
Unexpected type ‘Category (Src f)’
In the class declaration for ‘GHC.Classes.(%,%)’
A class declaration should have form
class GHC.Classes.(%,%) a b where ...
Prelude>
(%,%)
shouldn't show up here, same happens on 8.5.20180105