id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
1724,Type family and GADT error,Chris Kuklewicz,,"This bug was posted to glasgow-haskell-users@haskell.org by Roberto Zunino, archived at http://www.haskell.org/pipermail/glasgow-haskell-users/2007-September/013149.html
I am copying the post with the bug into trac:

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.",bug,closed,high,,Compiler (Type checker),6.9,duplicate,,,Unknown/Multiple,Unknown/Multiple,,Unknown,,,,