[GHC] #10461: Suggest UnliftedFFITypes when applicable

[GHC]

#10461: Suggest UnliftedFFITypes when applicable
-------------------------------------+-------------------------------------
              Reporter:  ezyang      |             Owner:  ezyang
                  Type:  bug         |            Status:  new
              Priority:  low         |         Milestone:
             Component:  Compiler    |           Version:  7.11
  (Type checker)                     |  Operating System:  Unknown/Multiple
              Keywords:              |   Type of failure:  Incorrect
          Architecture:              |  warning at compile-time
  Unknown/Multiple                   |        Blocked By:
             Test Case:              |   Related Tickets:
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
 Here's an example bad error message:

 {{{
 Serum.hs:5:1:
     Unacceptable result type in foreign declaration:
       ‘Word#’ cannot be marshalled in a foreign call
     When checking declaration:
       foreign import prim safe "static chenycopy" cheneycopy
         :: Any -> Word#

 }}}

 We should also add something like:

 {{{
     To enable marshalling unlifted types, enable -XUnliftedFFITypes
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10461>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler