Nested NPlusKPatterns

Nested patterns involving NPlusKPatterns cause a "parse error in pattern". Example appended below.

> {-# LANGUAGE NPlusKPatterns #-}
> {-# LANGUAGE ViewPatterns, PatternSynonyms #-}

> infix 1 :^:
>
> data Bush elem = Nil | Bud elem | Bush elem :^: Bush elem

> test ((n + 1) + 1) = n

> pattern DivMod2 ∷ (Integral nat) ⇒ nat → nat → nat
> pattern DivMod2 n k ← ((`divMod` 2) → (n, k)) where DivMod2 n k =  2 * n + k

> braun ∷ Integer → Bush ()
> braun (0)                = Nil
> braun (1)                = Bud ()
> braun (DivMod2 n k + 2)  = braun (n + k + 1) :^: braun (n + 1)