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Consider the following code:

{-# LANGUAGE PolyKinds,
             GADTs,
             DataKinds,
             KindSignatures
 #-}

data SList a where
  SNil :: SList '[]

x :: SList ('[] :: [Bool])
x = SNil

Compiling this code causes GHC to emit an error saying that AnyK cannot be unified with Bool. It seems that AnyK is a placeholder for an undetermined kind and that it should unify with any well-formed kind.

As a much smaller issue, the error emitted speaks about "types" where it means "kinds".

Trac metadata

Trac field	Value
Version	7.4.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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