Control.Exception.Safe

Please see the README.md file in the safe-exceptions repo for information on how to use this module. Relevant links:

• https://github.com/fpco/safe-exceptions#readme
• https://www.stackage.org/package/safe-exceptions

Throwing

throw :: (MonadThrow m, Exception e) => e -> m a

Synchronously throw the given exception

Since: 0.1.0.0

throwIO :: (MonadThrow m, Exception e) => e -> m a

Synonym for throw

Since: 0.1.0.0

throwM :: (MonadThrow m, Exception e) => e -> m a

Synonym for throw

Since: 0.1.0.0

throwString :: (MonadThrow m, HasCallStack) => String -> m a

A convenience function for throwing a user error. This is useful for cases where it would be too high a burden to define your own exception type.

This throws an exception of type StringException. When GHC supports it (base 4.9 and GHC 8.0 and onward), it includes a call stack.

Since: 0.1.5.0

data StringException

Exception type thrown by throwString.

Note that the second field of the data constructor depends on GHC/base version. For base 4.9 and GHC 8.0 and later, the second field is a call stack. Previous versions of GHC and base do not support call stacks, and the field is simply unit (provided to make pattern matching across GHC versions easier).

Since: 0.1.5.0

Constructors

StringException String CallStack

Instances

Show StringException

Methods

showsPrec :: Int -> StringException -> ShowS

show :: StringException -> String

showList :: [StringException] -> ShowS

Exception StringException

Methods

toException :: StringException -> SomeException

fromException :: SomeException -> Maybe StringException

displayException :: StringException -> String

throwTo :: (Exception e, MonadIO m) => ThreadId -> e -> m ()

Throw an asynchronous exception to another thread.

Synchronously typed exceptions will be wrapped into an AsyncExceptionWrapper, see https://github.com/fpco/safe-exceptions#determining-sync-vs-async

It's usually a better idea to use the async package, see https://github.com/fpco/safe-exceptions#quickstart

Since: 0.1.0.0

impureThrow :: Exception e => e -> a

Generate a pure value which, when forced, will synchronously throw the given exception

Generally it's better to avoid using this function and instead use throw, see https://github.com/fpco/safe-exceptions#quickstart

Since: 0.1.0.0

Catching (with recovery)

catch :: (MonadCatch m, Exception e) => m a -> (e -> m a) -> m a

Same as upstream catch, but will not catch asynchronous exceptions

Since: 0.1.0.0

catchIO :: MonadCatch m => m a -> (IOException -> m a) -> m a

catch specialized to only catching IOExceptions

Since: 0.1.3.0

catchAny :: MonadCatch m => m a -> (SomeException -> m a) -> m a

catch specialized to catch all synchronous exception

Since: 0.1.0.0

catchDeep :: (MonadCatch m, MonadIO m, Exception e, NFData a) => m a -> (e -> m a) -> m a

Same as catch, but fully force evaluation of the result value to find all impure exceptions.

Since: 0.1.1.0

catchAnyDeep :: (MonadCatch m, MonadIO m, NFData a) => m a -> (SomeException -> m a) -> m a

catchDeep specialized to catch all synchronous exception

Since: 0.1.1.0

catchAsync :: (MonadCatch m, Exception e) => m a -> (e -> m a) -> m a

catch without async exception safety

Generally it's better to avoid using this function since we do not want to recover from async exceptions, see https://github.com/fpco/safe-exceptions#quickstart

Since: 0.1.0.0

catchJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> m a -> (b -> m a) -> m a

catchJust is like catch but it takes an extra argument which is an exception predicate, a function which selects which type of exceptions we're interested in.

Since: 0.1.4.0

handle :: (MonadCatch m, Exception e) => (e -> m a) -> m a -> m a

Flipped version of catch

Since: 0.1.0.0

handleIO :: MonadCatch m => (IOException -> m a) -> m a -> m a

handle specialized to only catching IOExceptions

Since: 0.1.3.0

handleAny :: MonadCatch m => (SomeException -> m a) -> m a -> m a

Flipped version of catchAny

Since: 0.1.0.0

handleDeep :: (MonadCatch m, Exception e, MonadIO m, NFData a) => (e -> m a) -> m a -> m a

Flipped version of catchDeep

Since: 0.1.1.0

handleAnyDeep :: (MonadCatch m, MonadIO m, NFData a) => (SomeException -> m a) -> m a -> m a

Flipped version of catchAnyDeep

Since: 0.1.1.0

handleAsync :: (MonadCatch m, Exception e) => (e -> m a) -> m a -> m a

Flipped version of catchAsync

Generally it's better to avoid using this function since we do not want to recover from async exceptions, see https://github.com/fpco/safe-exceptions#quickstart

Since: 0.1.0.0

handleJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> (b -> m a) -> m a -> m a

Flipped catchJust.

Since: 0.1.4.0

try :: (MonadCatch m, Exception e) => m a -> m (Either e a)

Same as upstream try, but will not catch asynchronous exceptions

Since: 0.1.0.0

tryIO :: MonadCatch m => m a -> m (Either IOException a)

try specialized to only catching IOExceptions

Since: 0.1.3.0

tryAny :: MonadCatch m => m a -> m (Either SomeException a)

try specialized to catch all synchronous exceptions

Since: 0.1.0.0

tryDeep :: (MonadCatch m, MonadIO m, Exception e, NFData a) => m a -> m (Either e a)

Same as try, but fully force evaluation of the result value to find all impure exceptions.

Since: 0.1.1.0

tryAnyDeep :: (MonadCatch m, MonadIO m, NFData a) => m a -> m (Either SomeException a)

tryDeep specialized to catch all synchronous exceptions

Since: 0.1.1.0

tryAsync :: (MonadCatch m, Exception e) => m a -> m (Either e a)

try without async exception safety

Generally it's better to avoid using this function since we do not want to recover from async exceptions, see https://github.com/fpco/safe-exceptions#quickstart

Since: 0.1.0.0

tryJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> m a -> m (Either b a)

A variant of try that takes an exception predicate to select which exceptions are caught.

Since: 0.1.4.0

data Handler (m :: * -> *) a :: (* -> *) -> * -> * where

Generalized version of Handler

Constructors

Handler :: Handler m a

Instances

Monad m => Functor (Handler m)

Methods

fmap :: (a -> b) -> Handler m a -> Handler m b

(<$) :: a -> Handler m b -> Handler m a

catches :: (MonadCatch m, MonadThrow m) => m a -> [Handler m a] -> m a

Same as upstream catches, but will not catch asynchronous exceptions

Since: 0.1.2.0

catchesDeep :: (MonadCatch m, MonadThrow m, MonadIO m, NFData a) => m a -> [Handler m a] -> m a

Same as catches, but fully force evaluation of the result value to find all impure exceptions.

Since: 0.1.2.0

catchesAsync :: (MonadCatch m, MonadThrow m) => m a -> [Handler m a] -> m a

catches without async exception safety

Generally it's better to avoid using this function since we do not want to recover from async exceptions, see https://github.com/fpco/safe-exceptions#quickstart

Since: 0.1.2.0

Cleanup (no recovery)

onException :: MonadMask m => m a -> m b -> m a

Async safe version of onException

Since: 0.1.0.0

bracket :: forall m a b c. MonadMask m => m a -> (a -> m b) -> (a -> m c) -> m c

Async safe version of bracket

Since: 0.1.7.0

bracket_ :: MonadMask m => m a -> m b -> m c -> m c

Async safe version of bracket_

Since: 0.1.0.0

finally :: MonadMask m => m a -> m b -> m a

Async safe version of finally

Since: 0.1.0.0

withException :: (MonadMask m, Exception e) => m a -> (e -> m b) -> m a

Like onException, but provides the handler the thrown exception.

Since: 0.1.0.0

bracketOnError :: forall m a b c. MonadMask m => m a -> (a -> m b) -> (a -> m c) -> m c

Async safe version of bracketOnError

Since: 0.1.0.0

bracketOnError_ :: MonadMask m => m a -> m b -> m c -> m c

A variant of bracketOnError where the return value from the first computation is not required.

Since: 0.1.0.0

bracketWithError :: forall m a b c. MonadMask m => m a -> (Maybe SomeException -> a -> m b) -> (a -> m c) -> m c

Async safe version of bracket with access to the exception in the cleanup action.

Since: 0.1.0.0

Coercion to sync and async

data SyncExceptionWrapper

Wrap up an asynchronous exception to be treated as a synchronous exception

This is intended to be created via toSyncException

Since: 0.1.0.0

Constructors

Exception e => SyncExceptionWrapper e

Instances

Show SyncExceptionWrapper

Methods

showsPrec :: Int -> SyncExceptionWrapper -> ShowS

show :: SyncExceptionWrapper -> String

showList :: [SyncExceptionWrapper] -> ShowS

Exception SyncExceptionWrapper

Methods

toException :: SyncExceptionWrapper -> SomeException

fromException :: SomeException -> Maybe SyncExceptionWrapper

displayException :: SyncExceptionWrapper -> String

toSyncException :: Exception e => e -> SomeException

Convert an exception into a synchronous exception

For synchronous exceptions, this is the same as toException. For asynchronous exceptions, this will wrap up the exception with SyncExceptionWrapper

Since: 0.1.0.0

data AsyncExceptionWrapper

Wrap up a synchronous exception to be treated as an asynchronous exception

This is intended to be created via toAsyncException

Since: 0.1.0.0

Constructors

Exception e => AsyncExceptionWrapper e

Instances

Show AsyncExceptionWrapper

Methods

showsPrec :: Int -> AsyncExceptionWrapper -> ShowS

show :: AsyncExceptionWrapper -> String

showList :: [AsyncExceptionWrapper] -> ShowS

Exception AsyncExceptionWrapper

Methods

toException :: AsyncExceptionWrapper -> SomeException

fromException :: SomeException -> Maybe AsyncExceptionWrapper

displayException :: AsyncExceptionWrapper -> String

toAsyncException :: Exception e => e -> SomeException

Convert an exception into an asynchronous exception

For asynchronous exceptions, this is the same as toException. For synchronous exceptions, this will wrap up the exception with AsyncExceptionWrapper

Since: 0.1.0.0

Check exception type

isSyncException :: Exception e => e -> Bool

Check if the given exception is synchronous

Since: 0.1.0.0

isAsyncException :: Exception e => e -> Bool

Check if the given exception is asynchronous

Since: 0.1.0.0

Reexports

class Monad m => MonadThrow (m :: * -> *)

A class for monads in which exceptions may be thrown.

Instances should obey the following law:

throwM e >> x = throwM e

In other words, throwing an exception short-circuits the rest of the monadic computation.

Minimal complete definition

throwM

Instances

MonadThrow []

Methods

throwM :: Exception e => e -> [a]

MonadThrow Maybe

Methods

throwM :: Exception e => e -> Maybe a

MonadThrow IO

Methods

throwM :: Exception e => e -> IO a

MonadThrow Q

Methods

throwM :: Exception e => e -> Q a

MonadThrow STM

Methods

throwM :: Exception e => e -> STM a

(~) * e SomeException => MonadThrow (Either e)

Methods

throwM :: Exception e => e -> Either e a

MonadThrow m => MonadThrow (ListT m)

Methods

throwM :: Exception e => e -> ListT m a

MonadThrow m => MonadThrow (MaybeT m)

Throws exceptions into the base monad.

Methods

throwM :: Exception e => e -> MaybeT m a

(Error e, MonadThrow m) => MonadThrow (ErrorT e m)

Throws exceptions into the base monad.

Methods

throwM :: Exception e => e -> ErrorT e m a

MonadThrow m => MonadThrow (ExceptT e m)

Throws exceptions into the base monad.

Methods

throwM :: Exception e => e -> ExceptT e m a

MonadThrow m => MonadThrow (StateT s m)

Methods

throwM :: Exception e => e -> StateT s m a

MonadThrow m => MonadThrow (StateT s m)

Methods

throwM :: Exception e => e -> StateT s m a

(MonadThrow m, Monoid w) => MonadThrow (WriterT w m)

Methods

throwM :: Exception e => e -> WriterT w m a

(MonadThrow m, Monoid w) => MonadThrow (WriterT w m)

Methods

throwM :: Exception e => e -> WriterT w m a

MonadThrow m => MonadThrow (IdentityT * m)

Methods

throwM :: Exception e => e -> IdentityT * m a

MonadThrow m => MonadThrow (ContT * r m)

Methods

throwM :: Exception e => e -> ContT * r m a

MonadThrow m => MonadThrow (ReaderT * r m)

Methods

throwM :: Exception e => e -> ReaderT * r m a

(MonadThrow m, Monoid w) => MonadThrow (RWST r w s m)

Methods

throwM :: Exception e => e -> RWST r w s m a

(MonadThrow m, Monoid w) => MonadThrow (RWST r w s m)

Methods

throwM :: Exception e => e -> RWST r w s m a

class MonadThrow m => MonadCatch (m :: * -> *)

A class for monads which allow exceptions to be caught, in particular exceptions which were thrown by throwM.

Instances should obey the following law:

catch (throwM e) f = f e

Note that the ability to catch an exception does not guarantee that we can deal with all possible exit points from a computation. Some monads, such as continuation-based stacks, allow for more than just a success/failure strategy, and therefore catch cannot be used by those monads to properly implement a function such as finally. For more information, see MonadMask.

Minimal complete definition

catch

Instances

MonadCatch IO

Methods

catch :: Exception e => IO a -> (e -> IO a) -> IO a

MonadCatch STM

Methods

catch :: Exception e => STM a -> (e -> STM a) -> STM a

(~) * e SomeException => MonadCatch (Either e)

Since: 0.8.3

Methods

catch :: Exception e => Either e a -> (e -> Either e a) -> Either e a

MonadCatch m => MonadCatch (ListT m)

Methods

catch :: Exception e => ListT m a -> (e -> ListT m a) -> ListT m a

MonadCatch m => MonadCatch (MaybeT m)

Catches exceptions from the base monad.

Methods

catch :: Exception e => MaybeT m a -> (e -> MaybeT m a) -> MaybeT m a

(Error e, MonadCatch m) => MonadCatch (ErrorT e m)

Catches exceptions from the base monad.

Methods

catch :: Exception e => ErrorT e m a -> (e -> ErrorT e m a) -> ErrorT e m a

MonadCatch m => MonadCatch (ExceptT e m)

Catches exceptions from the base monad.

Methods

catch :: Exception e => ExceptT e m a -> (e -> ExceptT e m a) -> ExceptT e m a

MonadCatch m => MonadCatch (StateT s m)

Methods

catch :: Exception e => StateT s m a -> (e -> StateT s m a) -> StateT s m a

MonadCatch m => MonadCatch (StateT s m)

Methods

catch :: Exception e => StateT s m a -> (e -> StateT s m a) -> StateT s m a

(MonadCatch m, Monoid w) => MonadCatch (WriterT w m)

Methods

catch :: Exception e => WriterT w m a -> (e -> WriterT w m a) -> WriterT w m a

(MonadCatch m, Monoid w) => MonadCatch (WriterT w m)

Methods

catch :: Exception e => WriterT w m a -> (e -> WriterT w m a) -> WriterT w m a

MonadCatch m => MonadCatch (IdentityT * m)

Methods

catch :: Exception e => IdentityT * m a -> (e -> IdentityT * m a) -> IdentityT * m a

MonadCatch m => MonadCatch (ReaderT * r m)

Methods

catch :: Exception e => ReaderT * r m a -> (e -> ReaderT * r m a) -> ReaderT * r m a

(MonadCatch m, Monoid w) => MonadCatch (RWST r w s m)

Methods

catch :: Exception e => RWST r w s m a -> (e -> RWST r w s m a) -> RWST r w s m a

(MonadCatch m, Monoid w) => MonadCatch (RWST r w s m)

Methods

catch :: Exception e => RWST r w s m a -> (e -> RWST r w s m a) -> RWST r w s m a

class MonadCatch m => MonadMask (m :: * -> *) where

A class for monads which provide for the ability to account for all possible exit points from a computation, and to mask asynchronous exceptions. Continuation-based monads, and stacks such as ErrorT e IO which provide for multiple failure modes, are invalid instances of this class.

Note that this package does provide a MonadMask instance for CatchT. This instance is only valid if the base monad provides no ability to provide multiple exit. For example, IO or Either would be invalid base monads, but Reader or State would be acceptable.

Instances should ensure that, in the following code:

f `finally` g

The action g is called regardless of what occurs within f, including async exceptions.

Minimal complete definition

mask, uninterruptibleMask

Methods

mask :: ((forall a. m a -> m a) -> m b) -> m b

Runs an action with asynchronous exceptions disabled. The action is provided a method for restoring the async. environment to what it was at the mask call. See Control.Exception's mask.

uninterruptibleMask :: ((forall a. m a -> m a) -> m b) -> m b

Like mask, but the masked computation is not interruptible (see Control.Exception's uninterruptibleMask. WARNING: Only use if you need to mask exceptions around an interruptible operation AND you can guarantee the interruptible operation will only block for a short period of time. Otherwise you render the program/thread unresponsive and/or unkillable.

Instances

MonadMask IO

Methods

mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b

uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b

(~) * e SomeException => MonadMask (Either e)

Since: 0.8.3

Methods

mask :: ((forall a. Either e a -> Either e a) -> Either e b) -> Either e b

uninterruptibleMask :: ((forall a. Either e a -> Either e a) -> Either e b) -> Either e b

MonadMask m => MonadMask (StateT s m)

Methods

mask :: ((forall a. StateT s m a -> StateT s m a) -> StateT s m b) -> StateT s m b

uninterruptibleMask :: ((forall a. StateT s m a -> StateT s m a) -> StateT s m b) -> StateT s m b

MonadMask m => MonadMask (StateT s m)

Methods

mask :: ((forall a. StateT s m a -> StateT s m a) -> StateT s m b) -> StateT s m b

uninterruptibleMask :: ((forall a. StateT s m a -> StateT s m a) -> StateT s m b) -> StateT s m b

(MonadMask m, Monoid w) => MonadMask (WriterT w m)

Methods

mask :: ((forall a. WriterT w m a -> WriterT w m a) -> WriterT w m b) -> WriterT w m b

uninterruptibleMask :: ((forall a. WriterT w m a -> WriterT w m a) -> WriterT w m b) -> WriterT w m b

(MonadMask m, Monoid w) => MonadMask (WriterT w m)

Methods

mask :: ((forall a. WriterT w m a -> WriterT w m a) -> WriterT w m b) -> WriterT w m b

uninterruptibleMask :: ((forall a. WriterT w m a -> WriterT w m a) -> WriterT w m b) -> WriterT w m b

MonadMask m => MonadMask (IdentityT * m)

Methods

mask :: ((forall a. IdentityT * m a -> IdentityT * m a) -> IdentityT * m b) -> IdentityT * m b

uninterruptibleMask :: ((forall a. IdentityT * m a -> IdentityT * m a) -> IdentityT * m b) -> IdentityT * m b

MonadMask m => MonadMask (ReaderT * r m)

Methods

mask :: ((forall a. ReaderT * r m a -> ReaderT * r m a) -> ReaderT * r m b) -> ReaderT * r m b

uninterruptibleMask :: ((forall a. ReaderT * r m a -> ReaderT * r m a) -> ReaderT * r m b) -> ReaderT * r m b

(MonadMask m, Monoid w) => MonadMask (RWST r w s m)

Methods

mask :: ((forall a. RWST r w s m a -> RWST r w s m a) -> RWST r w s m b) -> RWST r w s m b

uninterruptibleMask :: ((forall a. RWST r w s m a -> RWST r w s m a) -> RWST r w s m b) -> RWST r w s m b

(MonadMask m, Monoid w) => MonadMask (RWST r w s m)

Methods

mask :: ((forall a. RWST r w s m a -> RWST r w s m a) -> RWST r w s m b) -> RWST r w s m b

uninterruptibleMask :: ((forall a. RWST r w s m a -> RWST r w s m a) -> RWST r w s m b) -> RWST r w s m b

mask_ :: MonadMask m => m a -> m a

Like mask, but does not pass a restore action to the argument.

uninterruptibleMask_ :: MonadMask m => m a -> m a

Like uninterruptibleMask, but does not pass a restore action to the argument.

catchIOError :: MonadCatch m => m a -> (IOError -> m a) -> m a

Catch all IOError (eqv. IOException) exceptions. Still somewhat too general, but better than using catchAll. See catchIf for an easy way of catching specific IOErrors based on the predicates in System.IO.Error.

handleIOError :: MonadCatch m => (IOError -> m a) -> m a -> m a

Flipped catchIOError

class (Typeable * e, Show e) => Exception e where

Any type that you wish to throw or catch as an exception must be an instance of the Exception class. The simplest case is a new exception type directly below the root:

data MyException = ThisException | ThatException
    deriving Show

instance Exception MyException

The default method definitions in the Exception class do what we need in this case. You can now throw and catch ThisException and ThatException as exceptions:

*Main> throw ThisException `catch` \e -> putStrLn ("Caught " ++ show (e :: MyException))
Caught ThisException

In more complicated examples, you may wish to define a whole hierarchy of exceptions:

---------------------------------------------------------------------
-- Make the root exception type for all the exceptions in a compiler

data SomeCompilerException = forall e . Exception e => SomeCompilerException e

instance Show SomeCompilerException where
    show (SomeCompilerException e) = show e

instance Exception SomeCompilerException

compilerExceptionToException :: Exception e => e -> SomeException
compilerExceptionToException = toException . SomeCompilerException

compilerExceptionFromException :: Exception e => SomeException -> Maybe e
compilerExceptionFromException x = do
    SomeCompilerException a <- fromException x
    cast a

---------------------------------------------------------------------
-- Make a subhierarchy for exceptions in the frontend of the compiler

data SomeFrontendException = forall e . Exception e => SomeFrontendException e

instance Show SomeFrontendException where
    show (SomeFrontendException e) = show e

instance Exception SomeFrontendException where
    toException = compilerExceptionToException
    fromException = compilerExceptionFromException

frontendExceptionToException :: Exception e => e -> SomeException
frontendExceptionToException = toException . SomeFrontendException

frontendExceptionFromException :: Exception e => SomeException -> Maybe e
frontendExceptionFromException x = do
    SomeFrontendException a <- fromException x
    cast a

---------------------------------------------------------------------
-- Make an exception type for a particular frontend compiler exception

data MismatchedParentheses = MismatchedParentheses
    deriving Show

instance Exception MismatchedParentheses where
    toException   = frontendExceptionToException
    fromException = frontendExceptionFromException

We can now catch a MismatchedParentheses exception as MismatchedParentheses, SomeFrontendException or SomeCompilerException, but not other types, e.g. IOException:

*Main> throw MismatchedParentheses catch e -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses catch e -> putStrLn ("Caught " ++ show (e :: SomeFrontendException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses catch e -> putStrLn ("Caught " ++ show (e :: SomeCompilerException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses catch e -> putStrLn ("Caught " ++ show (e :: IOException))
*** Exception: MismatchedParentheses

Methods

toException :: e -> SomeException

fromException :: SomeException -> Maybe e

displayException :: e -> String

Render this exception value in a human-friendly manner.

Default implementation: show.

Since: 4.8.0.0

Instances

Exception Void

Since: 4.8.0.0

Methods

toException :: Void -> SomeException

fromException :: SomeException -> Maybe Void

displayException :: Void -> String

Exception BlockedIndefinitelyOnMVar

Since: 4.1.0.0

Methods

toException :: BlockedIndefinitelyOnMVar -> SomeException

fromException :: SomeException -> Maybe BlockedIndefinitelyOnMVar

displayException :: BlockedIndefinitelyOnMVar -> String

Exception BlockedIndefinitelyOnSTM

Since: 4.1.0.0

Methods

toException :: BlockedIndefinitelyOnSTM -> SomeException

fromException :: SomeException -> Maybe BlockedIndefinitelyOnSTM

displayException :: BlockedIndefinitelyOnSTM -> String

Exception Deadlock

Since: 4.1.0.0

Methods

toException :: Deadlock -> SomeException

fromException :: SomeException -> Maybe Deadlock

displayException :: Deadlock -> String

Exception AllocationLimitExceeded

Since: 4.8.0.0

Methods

toException :: AllocationLimitExceeded -> SomeException

fromException :: SomeException -> Maybe AllocationLimitExceeded

displayException :: AllocationLimitExceeded -> String

Exception CompactionFailed

Since: 4.10.0.0

Methods

toException :: CompactionFailed -> SomeException

fromException :: SomeException -> Maybe CompactionFailed

displayException :: CompactionFailed -> String

Exception AssertionFailed

Since: 4.1.0.0

Methods

toException :: AssertionFailed -> SomeException

fromException :: SomeException -> Maybe AssertionFailed

displayException :: AssertionFailed -> String

Exception SomeAsyncException

Since: 4.7.0.0

Methods

toException :: SomeAsyncException -> SomeException

fromException :: SomeException -> Maybe SomeAsyncException

displayException :: SomeAsyncException -> String

Exception AsyncException

Since: 4.7.0.0

Methods

toException :: AsyncException -> SomeException

fromException :: SomeException -> Maybe AsyncException

displayException :: AsyncException -> String

Exception ArrayException

Since: 4.1.0.0

Methods

toException :: ArrayException -> SomeException

fromException :: SomeException -> Maybe ArrayException

displayException :: ArrayException -> String

Exception ExitCode

Since: 4.1.0.0

Methods

toException :: ExitCode -> SomeException

fromException :: SomeException -> Maybe ExitCode

displayException :: ExitCode -> String

Exception IOException

Since: 4.1.0.0

Methods

toException :: IOException -> SomeException

fromException :: SomeException -> Maybe IOException

displayException :: IOException -> String

Exception ErrorCall

Since: 4.0.0.0

Methods

toException :: ErrorCall -> SomeException

fromException :: SomeException -> Maybe ErrorCall

displayException :: ErrorCall -> String

Exception ArithException

Since: 4.0.0.0

Methods

toException :: ArithException -> SomeException

fromException :: SomeException -> Maybe ArithException

displayException :: ArithException -> String

Exception SomeException

Since: 3.0

Methods

toException :: SomeException -> SomeException

fromException :: SomeException -> Maybe SomeException

displayException :: SomeException -> String

Exception AsyncExceptionWrapper

Methods

toException :: AsyncExceptionWrapper -> SomeException

fromException :: SomeException -> Maybe AsyncExceptionWrapper

displayException :: AsyncExceptionWrapper -> String

Exception SyncExceptionWrapper

Methods

toException :: SyncExceptionWrapper -> SomeException

fromException :: SomeException -> Maybe SyncExceptionWrapper

displayException :: SyncExceptionWrapper -> String

Exception StringException

Methods

toException :: StringException -> SomeException

fromException :: SomeException -> Maybe StringException

displayException :: StringException -> String

class Typeable k (a :: k)

The class Typeable allows a concrete representation of a type to be calculated.

Minimal complete definition

typeRep#

data SomeException :: * where

The SomeException type is the root of the exception type hierarchy. When an exception of type e is thrown, behind the scenes it is encapsulated in a SomeException.

Constructors

SomeException :: SomeException

Instances

Show SomeException

Since: 3.0

Methods

showsPrec :: Int -> SomeException -> ShowS

show :: SomeException -> String

showList :: [SomeException] -> ShowS

Exception SomeException

Since: 3.0

Methods

toException :: SomeException -> SomeException

fromException :: SomeException -> Maybe SomeException

displayException :: SomeException -> String

data SomeAsyncException :: * where

Superclass for asynchronous exceptions.

Since: 4.7.0.0

Constructors

SomeAsyncException :: SomeAsyncException

Instances

Show SomeAsyncException

Since: 4.7.0.0

Methods

showsPrec :: Int -> SomeAsyncException -> ShowS

show :: SomeAsyncException -> String

showList :: [SomeAsyncException] -> ShowS

Exception SomeAsyncException

Since: 4.7.0.0

Methods

toException :: SomeAsyncException -> SomeException

fromException :: SomeException -> Maybe SomeAsyncException

displayException :: SomeAsyncException -> String

data IOException :: *

Exceptions that occur in the IO monad. An IOException records a more specific error type, a descriptive string and maybe the handle that was used when the error was flagged.

Instances

Eq IOException

Since: 4.1.0.0

Methods

(==) :: IOException -> IOException -> Bool

(/=) :: IOException -> IOException -> Bool

Show IOException

Since: 4.1.0.0

Methods

showsPrec :: Int -> IOException -> ShowS

show :: IOException -> String

showList :: [IOException] -> ShowS

Exception IOException

Since: 4.1.0.0

Methods

toException :: IOException -> SomeException

fromException :: SomeException -> Maybe IOException

displayException :: IOException -> String

Error IOException

Methods

noMsg :: IOException

strMsg :: String -> IOException

assert :: Bool -> a -> a

If the first argument evaluates to True, then the result is the second argument. Otherwise an AssertionFailed exception is raised, containing a String with the source file and line number of the call to assert.

Assertions can normally be turned on or off with a compiler flag (for GHC, assertions are normally on unless optimisation is turned on with -O or the -fignore-asserts option is given). When assertions are turned off, the first argument to assert is ignored, and the second argument is returned as the result.