Rebinding (:) -- built-in syntax, or just another constructor?

This program is valid in Hugs 2005, but not in GHC:

import Prelude (print,(<),Bool(..))

data Cond a = a : a

infixl 0 ?
infixl 1 :

(?) :: Bool -> Cond a -> a
True  ? (x : _) = x
False ? (_ : y) = y

main = print (1 < 2 ? "yeah" : "no!")

Hugs responds with:

Main> main
"yeah"

GHCi says:

$ ghci A.hs
A.hs:4:16: Illegal binding of built-in syntax: :

Which one is right?

Trac metadata

Trac field	Value
Version	6.6
Type	Bug
TypeOfFailure	OtherFailure
Priority	low
Resolution	Unresolved
Component	Compiler (Parser)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Multiple