Ill-sorted kinds crash GHC

GHC's sort-checker for kinds is not being terribly clever

{-# LANGUAGE PolyKinds, KindSignatures #-}
module Foo where

data T (a :: j k) = MkT

crashes the HEAD with

ghc-stage1: panic! (the 'impossible' happened)
  (GHC version 7.5 for x86_64-unknown-linux):
	kindFunResult ghc-prim:GHC.Prim.BOX{(w) tc 347}

Trac metadata

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