import GHC

import GHC.Paths ( libdir )

import DynFlags ( defaultLogAction )

main = 

    defaultErrorHandler defaultLogAction $ do

      runGhc (Just libdir) $ do

        dflags <- getSessionDynFlags

        setSessionDynFlags dflags

        target <- guessTarget "test_main.hs" Nothing

        setTargets [target]

        load LoadAllTargets

throws:

$> ghc -package ghc Main.hs

[1 of 1] Compiling Main             ( Main.hs, Main.o )

Main.hs:6:25:

    Couldn't match type `DynFlags' with `[Char]'

    Expected type: DynFlags.FatalMessager

      Actual type: DynFlags.LogAction

    In the first argument of `defaultErrorHandler', namely

      `defaultLogAction'

    In the expression: defaultErrorHandler defaultLogAction

    In the expression:

      defaultErrorHandler defaultLogAction

      $ do { runGhc (Just libdir)

             $ do { dflags <- getSessionDynFlags;

                    setSessionDynFlags dflags;

                    .... } }

Main.hs:7:7:

    Couldn't match expected type `DynFlags.FlushOut'

                with actual type `IO SuccessFlag'

    In a stmt of a 'do' block:

      runGhc (Just libdir)

      $ do { dflags <- getSessionDynFlags;

             setSessionDynFlags dflags;

             target <- guessTarget "test_main.hs" Nothing;

             setTargets [target];

             .... }

    In the second argument of `($)', namely

      `do { runGhc (Just libdir)

            $ do { dflags <- getSessionDynFlags;

                   setSessionDynFlags dflags;

                   .... } }'

    In the expression:

      defaultErrorHandler defaultLogAction

      $ do { runGhc (Just libdir)

             $ do { dflags <- getSessionDynFlags;

                    setSessionDynFlags dflags;

                    .... } }