FW: GHC as a library

[C.M.Brown]

Hi Kenny,

>
> \begin{code}
>
> main = do
>     session <- GHC.newSession GHC.JustTypecheck (Just "Test.hs")
>
>     dflags1 <- GHC.getSessionDynFlags session
>     (dflags2, packageIds) <- Packages.initPackages dflags1
>     GHC.setSessionDynFlags session dflags2{GHC.hscTarget=GHC.HscNothing}
>
>     let name = "Test.hs"
>     target <- GHC.guessTarget name Nothing
>     GHC.addTarget session target
>     GHC.load session GHC.LoadAllTargets
>
>     let preludeModule = GHC.mkModule (PackageConfig.stringToPackageId
> "base") (GHC.mkModuleName "Prelude")
>     GHC.setContext session [] [preludeModule]
>
>     m_checkedModule <- GHC.checkModule session (GHC.mkModuleName "Test")
>     ...
>
> \end{code}
>
> I am hoping to retrieve the inferred types of the declared Ids in Test.hs
> At this stage, what  I obtain is a value of type Maybe CheckedModule.

You can certainly get the type of an arbritrary expression in your project
module using something like the following:


ghcTypeCheck session expr modName =
  unsafePerformIO(
   do

       Just ty <- exprType session (modName ++ "." ++ expr)

       ty' <- cleanType ty
       return $ showSDoc $ ppr ty'
  )

cleanType ty = do
  return $! GHC.dropForAlls ty

That may be of some help...

Cheers,
Chris.