[GHC] #9197: FFI types should be usable in foreign import decls without revealing representations

[GHC]

#9197: FFI types should be usable in foreign import decls without revealing
representations
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        Reporter:  duncan            |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler (FFI)    |          Version:  7.8.2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by duncan):

 I suspect it does have something to do with `CTYPE`. I looked at the code
 for that a bit. It's clear that it associates a string (representing a C
 type) with a Haskell type to use in FFI generated headers. I couldn't
 immediately tell if it also does anything for declaring it as one of the
 known FFI types, but I suspect not. It may well be quite reasonable to
 give the `CTYPE` pragma the extra duty of allowing looking through
 newtypes, rather than using a builtin list.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9197#comment:4>
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