bogus error message deriving Show for unboxed types

[Julian Seward (Intl Vendor)]

This

   module M where
   import GlaExts

   data T = MkT Int# deriving Show

produces

   ShowBug.hs:5:
       Couldn't match `(*)' against `(#)'
           Expected kind: (*)
           Inferred kind: (#)
       When matching types `a' and `Int#'
           Expected type: a
           Inferred type: Int#

which is a noninsubstantially suboptimal error message.
(ghc = HEAD snapshot of about a week ago).

J