ghc-7.10.2: The GHC API

Safe HaskellNone




Ghc monad stuff

class (Functor m, MonadIO m, ExceptionMonad m, HasDynFlags m) => GhcMonad m where Source

A monad that has all the features needed by GHC API calls.

In short, a GHC monad

  • allows embedding of IO actions,
  • can log warnings,
  • allows handling of (extensible) exceptions, and
  • maintains a current session.

If you do not use Ghc or GhcT, make sure to call initGhcMonad before any call to the GHC API functions can occur.


newtype Ghc a Source

A minimal implementation of a GhcMonad. If you need a custom monad, e.g., to maintain additional state consider wrapping this monad or using GhcT.




unGhc :: Session -> IO a

newtype GhcT m a Source

A monad transformer to add GHC specific features to another monad.

Note that the wrapped monad must support IO and handling of exceptions.




unGhcT :: Session -> m a

liftGhcT :: Monad m => m a -> GhcT m a Source

reflectGhc :: Ghc a -> Session -> IO a Source

Reflect a computation in the Ghc monad into the IO monad.

You can use this to call functions returning an action in the Ghc monad inside an IO action. This is needed for some (too restrictive) callback arguments of some library functions:

libFunc :: String -> (Int -> IO a) -> IO a
ghcFunc :: Int -> Ghc a

ghcFuncUsingLibFunc :: String -> Ghc a -> Ghc a
ghcFuncUsingLibFunc str =
  reifyGhc $ \s ->
    libFunc $ \i -> do
      reflectGhc (ghcFunc i) s

reifyGhc :: (Session -> IO a) -> Ghc a Source

getSessionDynFlags :: GhcMonad m => m DynFlags Source

Grabs the DynFlags from the Session

liftIO :: MonadIO m => forall a. IO a -> m a Source

Lift a computation from the IO monad.

data Session Source

The Session is a handle to the complete state of a compilation session. A compilation session consists of a set of modules constituting the current program or library, the context for interactive evaluation, and various caches.


Session !(IORef HscEnv) 

withSession :: GhcMonad m => (HscEnv -> m a) -> m a Source

Call the argument with the current session.

modifySession :: GhcMonad m => (HscEnv -> HscEnv) -> m () Source

Set the current session to the result of applying the current session to the argument.

withTempSession :: GhcMonad m => (HscEnv -> HscEnv) -> m a -> m a Source

Call an action with a temporarily modified Session.


logWarnings :: GhcMonad m => WarningMessages -> m () Source

A monad that allows logging of warnings.

printException :: GhcMonad m => SourceError -> m () Source

Print the error message and all warnings. Useful inside exception handlers. Clears warnings after printing.

type WarnErrLogger = forall m. GhcMonad m => Maybe SourceError -> m () Source

A function called to log warnings and errors.