Kind polymorphism and promoted kinds is *not* an advertised feature of 7.4.1. Much code is there, but it doesn't work when you push it. The HEAD does work. If you are using kind polymorphism or promoted kinds, use HEAD (or a development snapshot).
Indeed not_okay compiles fine with HEAD
Simon
| -----Original Message-----
| From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-
| users-bounces@haskell.org] On Behalf Of David Menendez
| Sent: 06 June 2012 23:50
| To: José Pedro Magalhães
| Cc: glasgow-haskell-users@haskell.org Mailing List
| Subject: Re: Known problems with promoted tuples and lists in GHC 7.4.1?
|
| No, I'm just running 7.4.1.
|
| Here's a very stripped-down example of what I'm seeing:
|
| {-# LANGUAGE PolyKinds, DataKinds #-}
|
| data Pair a b = P a b
| data Nat = Z | S Nat
|
| data Phantom i = Phantom
|
| okay :: Phantom ('P Int Int)
| okay = Phantom
|
| -- not_okay :: Phantom '(Int, Int)
| -- not_okay = Phantom
|
| Uncommenting that last bit results in this error,
|
| Couldn't match kind `BOX' against `*'
| Kind incompatibility when matching types:
| k0 :: BOX
| (*, *) :: *
| In the expression: Phantom
| In an equation for `not_okay': not_okay = Phantom
|
| Something seems to have gone wrong internally.
|
|
| On Wed, Jun 6, 2012 at 5:43 PM, José Pedro Magalhães