type families + GADT = type unsafety?

20 Sep 2007

      (Trac reports "database locked", posting here...)

Here's unsafeCoerce:
...
type family Const a
type instance Const a = ()
data T a where T :: a -> T (Const a)
coerce :: forall a b . a -> b
coerce x = case T x :: T (Const b) of
           T y -> y
And this indeed "works"... Here's the result with the latest RC:

*TypeFam> coerce () 2
<interactive>: internal error: stg_ap_v_ret
    (GHC version 6.9.20070918 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Aborted

Regards,
Zun.

type families + GADT = type unsafety?

Roberto Zunino