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  • #11275

Closed
Open
Created Dec 22, 2015 by Ryan Scott@RyanGlScottMaintainer

:kind! doesn't reduce type families with poly-kinded return kinds

Originally discovered here, here is a simplified example:

$ ghci
GHCi, version 7.10.3: http://www.haskell.org/ghc/  :? for help
λ> :set -XPolyKinds -XTypeFamilies 
λ> type family Hm :: k where Hm = Int
λ> :kind! Hm
Hm :: k
= Hm

Giving Hm a monomorphic return kind of * makes it work with :kind!:

$ ghci
GHCi, version 7.10.3: http://www.haskell.org/ghc/  :? for help
λ> :set -XTypeFamilies 
λ> type family Hm :: * where Hm = Int
λ> :kind! Hm
Hm :: *
= Int
Trac metadata
Trac field Value
Version 7.10.3
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component GHCi
Test case
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