Safe Haskell	Safe
Language	Haskell98

Control.Monad.Exception.Throws

Description

Defines the Throws binary relationship between types.

Synopsis

class Exception e => Throws e l
data Caught e l
newtype CheckedException l = CheckedException {
- checkedException :: SomeException
}

Documentation

class Exception e => Throws e l Source #

Throws is a type level binary relationship used to model a list of exceptions.

There is only one case in which the user must add further instances to Throws. If your sets of exceptions are hierarchical then you need to teach Throws about the hierarchy.

Subtyping: As there is no way to automatically infer the subcases of an exception, they have to be encoded manually mirroring the hierarchy defined in the defined Exception instances. For example, the following instance encodes that MyFileNotFoundException is a subexception of MyIOException :

instance Throws MyFileNotFoundException (Caught MyIOException l)

Throws is not a transitive relation and every ancestor relation must be explicitly encoded.

                                                           --   TopException
                                                           --         |
  instance Throws MidException   (Caught TopException l)   --         |
                                                           --   MidException
  instance Throws ChildException (Caught MidException l)   --         |
  instance Throws ChildException (Caught TopException l)   --         |
                                                           --  ChildException

Note that SomeException is automatically an ancestor of every other exception type.

Instances

UncaughtException e => Throws e NoExceptions Source #
Instance details Defined in Control.Monad.Exception.Base
Exception e => Throws e AnyException Source #
Instance details Defined in Control.Monad.Exception.Base
Exception e => Throws e (Caught SomeException l) Source #	`SomeException` is at the top of the exception hierarchy . Capturing SomeException captures every possible exception
Instance details Defined in Control.Monad.Exception.Throws
Exception e => Throws e (Caught e l) Source #
Instance details Defined in Control.Monad.Exception.Throws
Throws e l => Throws e (Caught e' l) Source #
Instance details Defined in Control.Monad.Exception.Throws
Throws SomeException (Caught SomeException l) Source #
Instance details Defined in Control.Monad.Exception.Throws

data Caught e l Source #

A type level witness of a exception handler.

Instances

Exception e => Throws e (Caught SomeException l) Source #	`SomeException` is at the top of the exception hierarchy . Capturing SomeException captures every possible exception
Instance details Defined in Control.Monad.Exception.Throws
Exception e => Throws e (Caught e l) Source #
Instance details Defined in Control.Monad.Exception.Throws
Throws e l => Throws e (Caught e' l) Source #
Instance details Defined in Control.Monad.Exception.Throws
Throws SomeException (Caught SomeException l) Source #
Instance details Defined in Control.Monad.Exception.Throws
(Exception e, Monad m) => MonadCatch e (EMT (Caught e l) m) (EMT l m) Source #
Instance details Defined in Control.Monad.Exception.Pure Methods catch :: EMT (Caught e l) m a -> (e -> EMT l m a) -> EMT l m a Source # catchWithSrcLoc :: EMT (Caught e l) m a -> ([String] -> e -> EMT l m a) -> EMT l m a Source #
(Exception e, MonadBaseControl IO m) => MonadCatch e (EMT (Caught e l) m) (EMT l m) Source #
Instance details Defined in Control.Monad.Exception.IO Methods catch :: EMT (Caught e l) m a -> (e -> EMT l m a) -> EMT l m a Source # catchWithSrcLoc :: EMT (Caught e l) m a -> ([String] -> e -> EMT l m a) -> EMT l m a Source #

newtype CheckedException l Source #

CheckedException adds a phantom type parameter l to SomeException

Constructors

CheckedException
Fields checkedException :: SomeException

Instances

Show (CheckedException l) Source #
Instance details Defined in Control.Monad.Exception.Throws Methods showsPrec :: Int -> CheckedException l -> ShowS # show :: CheckedException l -> String # showList :: [CheckedException l] -> ShowS #