[GHC] #5610: Improve "Unacceptable argument type in foreign declaration" error message

[GHC]

#5610: Improve "Unacceptable argument type in foreign declaration" error message
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        Reporter:  bgamari                       |            Owner:
            Type:  feature request               |           Status:  new
        Priority:  high                          |        Milestone:
       Component:  Compiler (Type checker)       |          Version:
      Resolution:                                |  7.6.1-rc1
Operating System:  Unknown/Multiple              |         Keywords:
 Type of failure:  Incorrect warning at          |     Architecture:
  compile-time                                   |  Unknown/Multiple
       Test Case:                                |       Difficulty:
        Blocking:                                |  Unknown
                                                 |       Blocked By:
                                                 |  Related Tickets:
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"92587bfefea2b78f89bcdad27e0da5711463fd1b/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="92587bfefea2b78f89bcdad27e0da5711463fd1b"
 Refactor FFI error messages

 This patch was provoked by Trac #5610, which I finally got a moment to
 look at.

 In the end I added a new data type ErrUtils.Validity,

   data Validity
     = IsValid            -- Everything is fine
     | NotValid MsgDoc    -- A problem, and some indication of why

 with some suitable combinators, and used it where appropriate (which
 touches
 quite a few modules).  The main payoff is that error messages improve for
 FFI type validation.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5610#comment:24>
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