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A foreign import "wrapper" should have the form f -> IO (FunPtr f), and a foreign import "dynamic" should have the form FunPtr f -> f. GHC currently lacks these checks; the type argument to the FunPtr is ignored in both cases.

Ian Lynagh's example is below; we should be rejecting mkFun2 and mkCallback2.

module A where

import Foreign
import Foreign.C

data D = D

foreign import ccall "dynamic"
  mkFun1 :: FunPtr (CInt -> IO ()) -> (CInt -> IO ())

foreign import ccall "dynamic"
  mkFun2 :: FunPtr (D -> IO ()) -> (CInt -> IO ())

foreign import ccall "wrapper"
  mkCallBack1 :: IO () -> IO (FunPtr (IO ()))

foreign import ccall "wrapper"
  mkCallBack2 :: IO () -> IO (FunPtr D)

Trac metadata

Trac field	Value
Version	7.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (FFI)
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