| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
GHC.Driver.Monad
Contents
Synopsis
- class (Functor m, ExceptionMonad m, HasDynFlags m) => GhcMonad m where
- getSession :: m HscEnv
- setSession :: HscEnv -> m ()
- newtype Ghc a = Ghc {}
- newtype GhcT m a = GhcT {}
- liftGhcT :: m a -> GhcT m a
- reflectGhc :: Ghc a -> Session -> IO a
- reifyGhc :: (Session -> IO a) -> Ghc a
- getSessionDynFlags :: GhcMonad m => m DynFlags
- liftIO :: MonadIO m => IO a -> m a
- data Session = Session !(IORef HscEnv)
- withSession :: GhcMonad m => (HscEnv -> m a) -> m a
- modifySession :: GhcMonad m => (HscEnv -> HscEnv) -> m ()
- withTempSession :: GhcMonad m => (HscEnv -> HscEnv) -> m a -> m a
- logWarnings :: GhcMonad m => WarningMessages -> m ()
- printException :: GhcMonad m => SourceError -> m ()
- type WarnErrLogger = forall m. GhcMonad m => Maybe SourceError -> m ()
- defaultWarnErrLogger :: WarnErrLogger
Ghc monad stuff
class (Functor 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.
Instances
| GhcMonad Ghc # | |
Defined in GHC.Driver.Monad | |
| ExceptionMonad m => GhcMonad (GhcT m) # | |
Defined in GHC.Driver.Monad | |
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.
A monad transformer to add GHC specific features to another monad.
Note that the wrapped monad must support IO and handling of exceptions.
Instances
| Monad m => Monad (GhcT m) # | |
| Functor m => Functor (GhcT m) # | |
| Applicative m => Applicative (GhcT m) # | |
| MonadIO m => MonadIO (GhcT m) # | |
| MonadThrow m => MonadThrow (GhcT m) # | |
| MonadCatch m => MonadCatch (GhcT m) # | |
| MonadMask m => MonadMask (GhcT m) # | |
Defined in GHC.Driver.Monad | |
| MonadIO m => HasDynFlags (GhcT m) # | |
Defined in GHC.Driver.Monad Methods getDynFlags :: GhcT m DynFlags Source # | |
| ExceptionMonad m => GhcMonad (GhcT m) # | |
Defined in GHC.Driver.Monad | |
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) sgetSessionDynFlags :: GhcMonad m => m DynFlags Source #
Grabs the DynFlags from the Session
liftIO :: MonadIO m => IO a -> m a Source #
Lift a computation from the IO monad.
This allows us to run IO computations in any monadic stack, so long as it supports these kinds of operations
(i.e. IO is the base monad for the stack).
Example
import Control.Monad.Trans.State -- from the "transformers" library printState :: Show s => StateT s IO () printState = do state <- get liftIO $ print state
Had we omitted liftIO
• Couldn't match type ‘IO’ with ‘StateT s IO’ Expected type: StateT s IO () Actual type: IO ()
The important part here is the mismatch between StateT s IO () and IO ()
Luckily, we know of a function that takes an IO a(m a): liftIO
> evalStateT printState "hello" "hello" > evalStateT printState 3 3
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.
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.
Warnings
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.