#8588: ForeignImport coercion evaluated before typechecking ----------------------------------+---------------------------- 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: | ----------------------------------+---------------------------- 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_li... 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 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler