Like IO, but throws only PseudoException

Monads in which UIO computations may be embedded

Catch any exception but PseudoException in an IO action

Catch any e in an IO action, with a default mapping for unexpected cases

Re-embed UIO into MonadIO

Re-embed UIO and possible exception back into IO

You promise there are no exceptions but PseudoException thrown by this IO action

Every SomeException but PseudoException

Not everything handled by the exception system is a run-time error you can handle. This is the class of unrecoverable pseudo-exceptions.

Additionally, except for ExitCode any of these pseudo-exceptions you could never guarantee to have caught. Since they can come from anywhere at any time, we could never guarentee that UIO does not contain them.

Pseudo-exceptions caused by a programming error

Partial functions, error, undefined, etc

Pseudo-exceptions thrown by the runtime environment

When you're doing resource handling, PseudoException matters. You still need to use the bracket pattern to handle cleanup.

Mirrors forkFinally, but since the body is UIO, the thread must terminate successfully or because of PseudoException

Mirrors forkIO, but re-throws errors to the parent thread

• Ignores manual thread kills, since those are on purpose.
• Re-throws async exceptions (SomeAsyncException) as is.
• Re-throws ExitCode as is in an attempt to exit with the requested code.
• Wraps synchronous PseudoException in async ChildThreadError.

Async signal that a child thread ended due to non-async PseudoException