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I've wanted this for a while

ghci> :kind (:~:)
(:~:) :: k -> k -> Type

ghci> :kind (:~:) @(Type -> Type)
(:~:) @(Type -> Type) :: (Type -> Type) -> (Type -> Type) -> Type

ghci> :kind (:~:) @(Type -> Type) []
(:~:) @(Type -> Type) [] :: (Type -> Type) -> Type

ghci> :kind (:~:) @(Type -> Type) [] Maybe
(:~:) @(Type -> Type) [] Maybe :: Type

Working like

ghci> type Same k (a::k) (b::k) = a :~: b
ghci> :kind Same
Same :: forall k -> k -> k -> *

ghci> :kind Same (Type -> Type)
Same (Type -> Type) :: (Type -> Type) -> (Type -> Type) -> *
ghci> :kind Same (Type -> Type) []
Same (Type -> Type) [] :: (Type -> Type) -> *
ghci> :kind Same (Type -> Type) [] Maybe
Same (Type -> Type) [] Maybe :: *

Trac metadata

Trac field	Value
Version	8.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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