[GHC] #8588: ForeignImport coercion evaluated before typechecking

[GHC]

#8588: ForeignImport coercion evaluated before typechecking
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       Reporter:  zcourts         |             Owner:
           Type:  bug             |            Status:  new
       Priority:  normal          |         Milestone:
      Component:  Compiler        |           Version:  7.6.3
       Keywords:                  |  Operating System:  Windows
   Architecture:  x86_64 (amd64)  |   Type of failure:  Other
     Difficulty:  Unknown         |         Test Case:
     Blocked By:                  |          Blocking:
Related Tickets:                  |
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 I'm fairly new to Haskell by all accounts this could have been caused by
 me doing something silly. Following the real world haskell book's
 directions on the FFI resulted in:

 "Multiple markers at this line: - buildwrapper.exe: panic! (the
 'impossible' happened) (GHC version 7.6.3 for i386-unknown-mingw32):
 ForeignImport coercion evaluated before typechecking Please report this as
 a GHC bug: http://www.haskell.org/ghc/reportabug - 16 changed lines"

 I went to the Haskell Wiki to try an example from there to see if the RWH
 e.g. was just out dated. All examples I've come across causes this error
 inc. those at
 http://www.haskell.org/haskellwiki/FFI_complete_examples#Calling_standard_library_functions
 and reading https://www.haskell.org/ghc/docs/7.6.3/users_guide.pdf FFI
 section didn't help.

 The current failing code is

 {{{
 {-# LANGUAGE ForeignFunctionInterface #-}
 module Events.CEvent where
 import Prelude hiding (sin)

 import Foreign.C -- get the C types
 import Foreign.Ptr (Ptr,nullPtr)

 -- pure function
 foreign import ccall "sin" c_sin :: CDouble -> CDouble
 sin :: Double -> Double
 sin d = realToFrac (c_sin (realToFrac d))

 -- impure function
 foreign import ccall "time" c_time :: Ptr a -> IO CTime
 getTime :: IO CTime
 getTime = c_time nullPtr
 }}}

 I've also tried this which causes the same error

 {{{
 {-# LANGUAGE ForeignFunctionInterface #-}

 module Events.Event2 where
 import Foreign
 import Foreign.C.Types

 foreign import ccall "math.h sin"
      c_sin :: CDouble -> CDouble

 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8588>
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