universum-1.7.3: Custom prelude used in Serokell
Safe HaskellSafe
LanguageHaskell2010

Universum.Exception

Description

Re-exports most useful functionality from 'safe-exceptions'. Also provides some functions to work with exceptions over MonadError.

Synopsis

Documentation

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

Minimal complete definition

Nothing

Methods

toException :: e -> SomeException #

fromException :: SomeException -> Maybe e #

displayException :: e -> String #

Render this exception value in a human-friendly manner.

Default implementation: show.

Since: base-4.8.0.0

Instances

Instances details
Exception Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Exception PatternMatchFail

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecSelError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecConError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecUpdError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception NoMethodError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception TypeError

Since: base-4.9.0.0

Instance details

Defined in Control.Exception.Base

Exception NonTermination

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception NestedAtomically

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception BlockedIndefinitelyOnMVar

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception BlockedIndefinitelyOnSTM

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception Deadlock

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception AllocationLimitExceeded

Since: base-4.8.0.0

Instance details

Defined in GHC.IO.Exception

Exception CompactionFailed

Since: base-4.10.0.0

Instance details

Defined in GHC.IO.Exception

Exception AssertionFailed

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception SomeAsyncException

Since: base-4.7.0.0

Instance details

Defined in GHC.IO.Exception

Exception AsyncException

Since: base-4.7.0.0

Instance details

Defined in GHC.IO.Exception

Exception ArrayException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception FixIOException

Since: base-4.11.0.0

Instance details

Defined in GHC.IO.Exception

Exception ExitCode

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception IOException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception ErrorCall

Since: base-4.0.0.0

Instance details

Defined in GHC.Exception

Exception ArithException

Since: base-4.0.0.0

Instance details

Defined in GHC.Exception.Type

Exception SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

Exception StringException 
Instance details

Defined in Control.Exception.Safe

Exception SyncExceptionWrapper 
Instance details

Defined in Control.Exception.Safe

Exception AsyncExceptionWrapper 
Instance details

Defined in Control.Exception.Safe

Exception UnicodeException 
Instance details

Defined in Data.Text.Encoding.Error

Exception Bug Source # 
Instance details

Defined in Universum.Exception

data SomeException #

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

Exception e => SomeException e 

Instances

Instances details
Show SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

Exception SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

class Monad m => MonadThrow (m :: Type -> Type) #

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

Instances details
MonadThrow [] 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadThrow Maybe 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadThrow IO 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadThrow Q 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadThrow STM 
Instance details

Defined in Control.Monad.Catch

Methods

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

e ~ SomeException => MonadThrow (Either e) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e0 => e0 -> Either e a #

MonadThrow (ST s) 
Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> ST s a #

MonadThrow m => MonadThrow (MaybeT m)

Throws exceptions into the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

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

MonadThrow m => MonadThrow (ListT m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadThrow m => MonadThrow (ExceptT e m)

Throws exceptions into the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e0 => e0 -> ExceptT e m a #

MonadThrow m => MonadThrow (StateT s m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadThrow m => MonadThrow (ReaderT r m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadThrow m => MonadThrow (IdentityT m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

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

Throws exceptions into the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e0 => e0 -> ErrorT e m a #

MonadThrow m => MonadThrow (StateT s m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

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

Defined in Control.Monad.Catch

Methods

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

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

Defined in Control.Monad.Catch

Methods

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

MonadThrow m => MonadThrow (ContT r m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

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

Defined in Control.Monad.Catch

Methods

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

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

Defined in Control.Monad.Catch

Methods

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

class MonadThrow m => MonadCatch (m :: Type -> Type) #

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

Instances details
MonadCatch IO 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadCatch STM 
Instance details

Defined in Control.Monad.Catch

Methods

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

e ~ SomeException => MonadCatch (Either e)

Since: exceptions-0.8.3

Instance details

Defined in Control.Monad.Catch

Methods

catch :: Exception e0 => Either e a -> (e0 -> Either e a) -> Either e a #

MonadCatch m => MonadCatch (MaybeT m)

Catches exceptions from the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

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

MonadCatch m => MonadCatch (ListT m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadCatch m => MonadCatch (ExceptT e m)

Catches exceptions from the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

catch :: Exception e0 => ExceptT e m a -> (e0 -> ExceptT e m a) -> ExceptT e m a #

MonadCatch m => MonadCatch (StateT s m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadCatch m => MonadCatch (ReaderT r m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

MonadCatch m => MonadCatch (IdentityT m) 
Instance details

Defined in Control.Monad.Catch

Methods

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

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

Catches exceptions from the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

catch :: Exception e0 => ErrorT e m a -> (e0 -> ErrorT e m a) -> ErrorT e m a #

MonadCatch m => MonadCatch (StateT s m) 
Instance details

Defined in Control.Monad.Catch

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) 
Instance details

Defined in Control.Monad.Catch

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) 
Instance details

Defined in Control.Monad.Catch

Methods

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

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

Defined in Control.Monad.Catch

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) 
Instance details

Defined in Control.Monad.Catch

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 :: Type -> Type) 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 are invalid instances of this class.

Instances should ensure that, in the following code:

fg = f `finally` g

The action g is called regardless of what occurs within f, including async exceptions. Some monads allow f to abort the computation via other effects than throwing an exception. For simplicity, we will consider aborting and throwing an exception to be two forms of "throwing an error".

If f and g both throw an error, the error thrown by fg depends on which errors we're talking about. In a monad transformer stack, the deeper layers override the effects of the inner layers; for example, ExceptT e1 (Except e2) a represents a value of type Either e2 (Either e1 a), so throwing both an e1 and an e2 will result in Left e2. If f and g both throw an error from the same layer, instances should ensure that the error from g wins.

Effects other than throwing an error are also overriden by the deeper layers. For example, StateT s Maybe a represents a value of type s -> Maybe (a, s), so if an error thrown from f causes this function to return Nothing, any changes to the state which f also performed will be erased. As a result, g will see the state as it was before f. Once g completes, f's error will be rethrown, so g' state changes will be erased as well. This is the normal interaction between effects in a monad transformer stack.

By contrast, lifted-base's version of finally always discards all of g's non-IO effects, and g never sees any of f's non-IO effects, regardless of the layer ordering and regardless of whether f throws an error. This is not the result of interacting effects, but a consequence of MonadBaseControl's approach.

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.

generalBracket #

Arguments

:: m a

acquire some resource

-> (a -> ExitCase b -> m c)

release the resource, observing the outcome of the inner action

-> (a -> m b)

inner action to perform with the resource

-> m (b, c) 

A generalized version of bracket which uses ExitCase to distinguish the different exit cases, and returns the values of both the use and release actions. In practice, this extra information is rarely needed, so it is often more convenient to use one of the simpler functions which are defined in terms of this one, such as bracket, finally, onError, and bracketOnError.

This function exists because in order to thread their effects through the execution of bracket, monad transformers need values to be threaded from use to release and from release to the output value.

NOTE This method was added in version 0.9.0 of this library. Previously, implementation of functions like bracket and finally in this module were based on the mask and uninterruptibleMask functions only, disallowing some classes of tranformers from having MonadMask instances (notably multi-exit-point transformers like ExceptT). If you are a library author, you'll now need to provide an implementation for this method. The StateT implementation demonstrates most of the subtleties:

generalBracket acquire release use = StateT $ s0 -> do
  ((b, _s2), (c, s3)) <- generalBracket
    (runStateT acquire s0)
    ((resource, s1) exitCase -> case exitCase of
      ExitCaseSuccess (b, s2) -> runStateT (release resource (ExitCaseSuccess b)) s2

      -- In the two other cases, the base monad overrides use's state
      -- changes and the state reverts to s1.
      ExitCaseException e     -> runStateT (release resource (ExitCaseException e)) s1
      ExitCaseAbort           -> runStateT (release resource ExitCaseAbort) s1
    )
    ((resource, s1) -> runStateT (use resource) s1)
  return ((b, c), s3)

The StateT s m implementation of generalBracket delegates to the m implementation of generalBracket. The acquire, use, and release arguments given to StateT's implementation produce actions of type StateT s m a, StateT s m b, and StateT s m c. In order to run those actions in the base monad, we need to call runStateT, from which we obtain actions of type m (a, s), m (b, s), and m (c, s). Since each action produces the next state, it is important to feed the state produced by the previous action to the next action.

In the ExitCaseSuccess case, the state starts at s0, flows through acquire to become s1, flows through use to become s2, and finally flows through release to become s3. In the other two cases, release does not receive the value s2, so its action cannot see the state changes performed by use. This is fine, because in those two cases, an error was thrown in the base monad, so as per the usual interaction between effects in a monad transformer stack, those state changes get reverted. So we start from s1 instead.

Finally, the m implementation of generalBracket returns the pairs (b, s) and (c, s). For monad transformers other than StateT, this will be some other type representing the effects and values performed and returned by the use and release actions. The effect part of the use result, in this case _s2, usually needs to be discarded, since those effects have already been incorporated in the release action.

The only effect which is intentionally not incorporated in the release action is the effect of throwing an error. In that case, the error must be re-thrown. One subtlety which is easy to miss is that in the case in which use and release both throw an error, the error from release should take priority. Here is an implementation for ExceptT which demonstrates how to do this.

generalBracket acquire release use = ExceptT $ do
  (eb, ec) <- generalBracket
    (runExceptT acquire)
    (eresource exitCase -> case eresource of
      Left e -> return (Left e) -- nothing to release, acquire didn't succeed
      Right resource -> case exitCase of
        ExitCaseSuccess (Right b) -> runExceptT (release resource (ExitCaseSuccess b))
        ExitCaseException e       -> runExceptT (release resource (ExitCaseException e))
        _                         -> runExceptT (release resource ExitCaseAbort))
    (either (return . Left) (runExceptT . use))
  return $ do
    -- The order in which we perform those two Either effects determines
    -- which error will win if they are both Lefts. We want the error from
    -- release to win.
    c <- ec
    b <- eb
    return (b, c)

Since: exceptions-0.9.0

Instances

Instances details
MonadMask IO 
Instance details

Defined in Control.Monad.Catch

Methods

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

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

generalBracket :: IO a -> (a -> ExitCase b -> IO c) -> (a -> IO b) -> IO (b, c) #

e ~ SomeException => MonadMask (Either e)

Since: exceptions-0.8.3

Instance details

Defined in Control.Monad.Catch

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 #

generalBracket :: Either e a -> (a -> ExitCase b -> Either e c) -> (a -> Either e b) -> Either e (b, c) #

MonadMask m => MonadMask (MaybeT m)

Since: exceptions-0.10.0

Instance details

Defined in Control.Monad.Catch

Methods

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

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

generalBracket :: MaybeT m a -> (a -> ExitCase b -> MaybeT m c) -> (a -> MaybeT m b) -> MaybeT m (b, c) #

MonadMask m => MonadMask (ExceptT e m)

Since: exceptions-0.9.0

Instance details

Defined in Control.Monad.Catch

Methods

mask :: ((forall a. ExceptT e m a -> ExceptT e m a) -> ExceptT e m b) -> ExceptT e m b #

uninterruptibleMask :: ((forall a. ExceptT e m a -> ExceptT e m a) -> ExceptT e m b) -> ExceptT e m b #

generalBracket :: ExceptT e m a -> (a -> ExitCase b -> ExceptT e m c) -> (a -> ExceptT e m b) -> ExceptT e m (b, c) #

MonadMask m => MonadMask (StateT s m) 
Instance details

Defined in Control.Monad.Catch

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 #

generalBracket :: StateT s m a -> (a -> ExitCase b -> StateT s m c) -> (a -> StateT s m b) -> StateT s m (b, c) #

MonadMask m => MonadMask (ReaderT r m) 
Instance details

Defined in Control.Monad.Catch

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 #

generalBracket :: ReaderT r m a -> (a -> ExitCase b -> ReaderT r m c) -> (a -> ReaderT r m b) -> ReaderT r m (b, c) #

MonadMask m => MonadMask (IdentityT m) 
Instance details

Defined in Control.Monad.Catch

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 #

generalBracket :: IdentityT m a -> (a -> ExitCase b -> IdentityT m c) -> (a -> IdentityT m b) -> IdentityT m (b, c) #

(Error e, MonadMask m) => MonadMask (ErrorT e m) 
Instance details

Defined in Control.Monad.Catch

Methods

mask :: ((forall a. ErrorT e m a -> ErrorT e m a) -> ErrorT e m b) -> ErrorT e m b #

uninterruptibleMask :: ((forall a. ErrorT e m a -> ErrorT e m a) -> ErrorT e m b) -> ErrorT e m b #

generalBracket :: ErrorT e m a -> (a -> ExitCase b -> ErrorT e m c) -> (a -> ErrorT e m b) -> ErrorT e m (b, c) #

MonadMask m => MonadMask (StateT s m) 
Instance details

Defined in Control.Monad.Catch

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 #

generalBracket :: StateT s m a -> (a -> ExitCase b -> StateT s m c) -> (a -> StateT s m b) -> StateT s m (b, c) #

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

Defined in Control.Monad.Catch

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 #

generalBracket :: WriterT w m a -> (a -> ExitCase b -> WriterT w m c) -> (a -> WriterT w m b) -> WriterT w m (b, c) #

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

Defined in Control.Monad.Catch

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 #

generalBracket :: WriterT w m a -> (a -> ExitCase b -> WriterT w m c) -> (a -> WriterT w m b) -> WriterT w m (b, c) #

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

Defined in Control.Monad.Catch

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 #

generalBracket :: RWST r w s m a -> (a -> ExitCase b -> RWST r w s m c) -> (a -> RWST r w s m b) -> RWST r w s m (b, c) #

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

Defined in Control.Monad.Catch

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 #

generalBracket :: RWST r w s m a -> (a -> ExitCase b -> RWST r w s m c) -> (a -> RWST r w s m b) -> RWST r w s m (b, c) #

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

Async safe version of bracketOnError

Since: safe-exceptions-0.1.0.0

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

Async safe version of finally

Since: safe-exceptions-0.1.0.0

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

Async safe version of bracket_

Since: safe-exceptions-0.1.0.0

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

Async safe version of bracket

Since: safe-exceptions-0.1.0.0

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

Async safe version of onException

Since: safe-exceptions-0.1.0.0

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

try specialized to catch all synchronous exceptions

Since: safe-exceptions-0.1.0.0

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

Same as upstream try, but will not catch asynchronous exceptions

Since: safe-exceptions-0.1.0.0

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

Flipped version of catchAny

Since: safe-exceptions-0.1.0.0

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

catch specialized to catch all synchronous exception

Since: safe-exceptions-0.1.0.0

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

Same as upstream catch, but will not catch asynchronous exceptions

Since: safe-exceptions-0.1.0.0

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

Synonym for throw

Since: safe-exceptions-0.1.0.0

data Bug Source #

Type that represents exceptions used in cases when a particular codepath is not meant to be ever executed, but happens to be executed anyway.

Instances

Instances details
Show Bug Source # 
Instance details

Defined in Universum.Exception

Methods

showsPrec :: Int -> Bug -> ShowS #

show :: Bug -> String #

showList :: [Bug] -> ShowS #

Exception Bug Source # 
Instance details

Defined in Universum.Exception

bug :: (HasCallStack, Exception e) => e -> a Source #

Generate a pure value which, when forced, will synchronously throw the exception wrapped into Bug data type.

pattern Exc :: Exception e => e -> SomeException Source #

Pattern synonym to easy pattern matching on exceptions. So intead of writing something like this:

isNonCriticalExc e
    | Just (_ :: NodeAttackedError) <- fromException e = True
    | Just DialogUnexpected{} <- fromException e = True
    | otherwise = False

you can use Exc pattern synonym:

isNonCriticalExc = case
    Exc (_ :: NodeAttackedError) -> True  -- matching all exceptions of type NodeAttackedError
    Exc DialogUnexpected{} -> True
    _ -> False

This pattern is bidirectional. You can use Exc e instead of toException e.

note :: MonadError e m => e -> Maybe a -> m a Source #

Throws error for Maybe if Nothing is given. Operates over MonadError.