New type of ($) operator in GHC 8.0 is problematic

Christopher Allen cma at
Thu Feb 4 18:21:23 UTC 2016

$ ghci
:lGHCi, version  :? for help
 Loaded GHCi configuration from /home/callen/.ghci

Prelude> :t ($)
  :: forall (w :: GHC.Types.Levity) a (b :: TYPE w).
     (a -> b) -> a -> b

As someone that's working on a book for beginners/intermediates and that
mentions ($) early'ish, this is pretty disconcerting. Particularly as we're
not going to explain Levity or TYPE. Is this intentional? My only ~/.ghci
flag is fno-warn-type-defaults.

Apologies if this is a mix-up on my part.

--- Chris
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