GHCi: internal error: stg_ap_p_ret

import Unsafe.Coerce
coerce = Unsafe.Coerce.unsafeCoerce

data Nat = Zero | Suc Nat

fromNat :: Nat -> Integer
fromNat Zero    = 0
fromNat (Suc l) = 1 + fromNat l

instance Show Nat where
  show l = show (fromNat l)

data Exp = Const Nat | Pred | App Exp Exp

eval :: Exp -> a
eval (Const n) = coerce n
eval e         = coerce $ evalP e
  where
    evalP Pred Zero    = Zero
    evalP Pred (Suc n) = n
    evalP e    n       = evalA e n

    evalA (App f e)    = eval f (eval e)
    evalA _            = error "eval"

-- With type signature, result is 0 (wrong, should be 1)
-- Without type signature: internal error: stg_ap_p_ret
-- test :: Nat
test = eval $ App Pred $ Const $ Suc $ Suc Zero

-- main prints 0 should maybe print 1
main :: IO ()
main = print (coerce test :: Nat)

when evaluatiing test at the ghci prompt after loading, I get

<interactive>: internal error: stg_ap_p_ret
    (GHC version 7.8.3 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Process haskell aborted (core dumped)

Trac metadata

Trac field	Value
Version	7.8.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
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CC	hvr
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