[Haskell-cafe] GHC API gives a weird error about .hi-boot files

15 Aug 2011

      Can anyone tell me what I'm doing wrong with the GHC API?  I'm getting
the following error message from the GHC API:

    Can't find interface-file declaration for variable Main.picture
      Probable cause: bug in .hi-boot file, or inconsistent .hi file
      Use -ddump-if-trace to get an idea of which file caused the error

The source code I'm loading doesn't seem to matter at all, except that
it defines a top-level variable called 'picture'.  Of course, if I
change the module name then I get a different module name in the error,
but that's about it.

The code I'm using to load the file is as follows:

getPicture src = do
    fn <- chooseFileName ".hs"
    B.writeFile fn src
    codeErrors <- newIORef []
    GHC.defaultErrorHandler (addErrorTo codeErrors)
        $ GHC.runGhc (Just GHC.libdir)
        $ GHC.handleSourceError (handle codeErrors) $ do
            dflags <- GHC.getSessionDynFlags
            GHC.setSessionDynFlags $ dflags {
                GHC.ghcMode = GHC.OneShot,
                GHC.ghcLink = GHC.LinkInMemory,
                GHC.hscTarget = GHC.HscInterpreted,
                GHC.log_action = addErrorTo codeErrors
                }
            target <- GHC.guessTarget fn Nothing
            GHC.setTargets [target]
            r <- fmap GHC.succeeded (GHC.load GHC.LoadAllTargets)
            case r of
                True -> do
                    mods <- GHC.getModuleGraph
                    GHC.setContext
                        [ GHC.ms_mod (head mods) ]
                        [ GHC.simpleImportDecl
                            (GHC.mkModuleName "Graphics.Gloss") ]
                    v <- GHC.compileExpr "picture :: Picture"
                    return (Right (unsafeCoerce# v :: Picture))
                False -> return (Left codeErrors)

I can't see anything I'm doing obviously wrong here, but I'm not at all
familiar with GHC's build process, so I'm hoping someone can pipe up and
point out the obvious stuff I've missed.

Any ideas?

-- 
Chris Smith