IO without any PseudoException

Polymorphic base without any PseudoException

Catch any exception but PseudoException in an IO action

Re-embed UIO into MonadIO

Re-embed UIO and possible exception back into IO

You promise that e covers all exceptions but PseudoException thrown by this IO action

This function is partial if you lie

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 pseudo-exceptions you usually can do nothing about, just log or exit.

Additionally, except for ExitCode any of these psuedo-exceptions you could never guarentee 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 any PseudoException to the parent thread