Couldn't match kind `BOX' against `*' when using SOURCE import

[atnnn]

When this module has a (useless) SOURCE import, using its typeclass gives an error.

module Bar where
import {-# SOURCE #-} Foo
class Bar a (p :: Bool) | a -> p
data Proxy a = Proxy

With the interpreter, the error appears when using the class:

Prelude> :l Bar
*Bar> :set -XFlexibleContexts -XDataKinds
*Bar> Proxy :: Bar '() a => Proxy a
    Couldn't match kind `BOX' against `*'
    Kind incompatibility when matching types:
      k0 :: BOX
      Bool :: *

When compiling, the error appears the *second* run.

$ ghc Main.hs
No instance for (Bar () '() a0)
$ ghc Main.hs
Couldn't match kind `BOX' against `*'

Tested with 7.4.1 and HEAD

[simonpj@…]

commit e57c8667363a60164b3505f22ddd25a9d5be32f5

Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Mon Apr 30 13:40:23 2012 +0100

    Make the interface-file deserialisation work right for promoted types (Trac #6054)
    
    GHC currently uses the slightly-dodgy plan that when we proote
    a TyCon to be a Kind constructor we leave it with the same Name.
    
    That means that to make sense of a IfaceType we need to know wheter
    it is really an IfaceType or an IfaceKind, because in the latter an
    occurrence of (say) Maybe will be the *promoted* Maybe.
    
    See Note [Checking IfaceTypes vs IfaceKinds] in TcIface

 compiler/iface/TcIface.lhs |   73 +++++++++++++++++++++++++++++++++++++++----
 1 files changed, 66 insertions(+), 7 deletions(-)

[simonpj]

Thanks for identifying this!