[GHC] #7408: Do not warn on unused newtype constructors when used with FFI

[GHC]

#7408: Do not warn on unused newtype constructors when used with FFI
---------------------------------+------------------------------------------
    Reporter:  SimonHengel       |       Owner:                  
        Type:  feature request   |      Status:  new             
    Priority:  normal            |   Milestone:                  
   Component:  Compiler          |     Version:  7.6.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Changes (by simonpj):

  * difficulty:  => Unknown


Comment:

 commit c8f4f50983bbb26b2d753e56ba61f5a307ff412f
 {{{
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Mon Nov 26 12:05:21 2012 +0000

     Accurately report usage of newtype data constructors in FFI
 declarations

     See Note [Newtype constructor usage in foreign declarations] in
 TcForeign.
     It's quite non-trivial to say which newtype constructor are used in
     foreign import/export declarations, and I had to do a bit of
 refactoring
     to achieve it.  (Say hello to the X5 bus from Oxford to Cambridge.)
     It's a bit tiresome, with some more plumbing, but not hard.

     Trac #7048 triggered this change.

  compiler/rename/RnNames.lhs       |    6 +-
  compiler/typecheck/TcForeign.lhs  |  164
 +++++++++++++++++++-----------------
  compiler/typecheck/TcRnDriver.lhs |   29 ++++++-
  compiler/typecheck/TcRnTypes.lhs  |   38 ++++++---
  4 files changed, 142 insertions(+), 95 deletions(-)
 }}}
 (The "7048" should be "7408".)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7408#comment:1>
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