[GHC] #12705: Renamer should reject signatures that reexport only part of a declaration

[GHC]

#12705: Renamer should reject signatures that reexport only part of a declaration
-------------------------------------+-------------------------------------
           Reporter:  ezyang         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  low            |         Milestone:
          Component:  Compiler       |           Version:  8.1
  (Type checker)                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The following signature is bogus, and also, unfortunately, accepted by GHC
 at the moment:

 {{{
 signature A(f) where
 data T = MkT { f :: Bool }
 }}}

 This doesn't make any sense at all. We should reject it early. It can lead
 to very strange errors (see bkpreex05 in tree) but happily it is fairly
 easy to avoid.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12705>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler