core lint error with arrow notation and GADTs

The following code panics GHC (with 7.0.3, 7.2 and 7.4.0.20111219):

{-# LANGUAGE Arrows, GADTs #-}
import Control.Arrow

data Value a where BoolVal :: Value Bool

class ArrowInit f where
    arrif :: f b -> ()

instance ArrowInit Value where
    arrif = proc BoolVal -> returnA -< ()
    -- arrif = arr (\BoolVal -> ())

I am attaching the -dcore-lint from 7.4.

Trac metadata

Trac field	Value
Version	7.4.1-rc1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ben@moseley.name, benjamin.moseley@barclayscapital.com
Operating system	MacOS X
Architecture	x86