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{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-- Tests newtype unwrapping for the IO monad itself
-- Notice the RenderM monad, which is used in the
-- type of the callback function
module ShouldCompile where
import Foreign.Ptr
newtype RenderM a = RenderM (IO a) deriving (Functor, Monad)
type RenderCallback = Int -> Int -> RenderM ()
foreign import ccall duma_onRender :: FunPtr RenderCallback -> RenderM ()
foreign import ccall "wrapper" mkRenderCallback
:: RenderCallback -> RenderM (FunPtr RenderCallback)
onRender :: RenderCallback -> RenderM ()
onRender f = mkRenderCallback f >>= duma_onRender
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