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 |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | hvr |
Operating system | |
Architecture |