Cause: inspect defects

When an effect fails with an unexpected error Cause defines everything that may have caused the issue:

• Fail<E>: when we do not recover from an expected error
• Die: when an effect cannot recover or continue, hitting a dead end (for example when using throw or by manually calling Effect.die or Effect.dieMessage)
• Interrupt: when an interrupt signal stops the execution of the effect (for example by using Effect.interrupt)
• Sequential<E> | Parallel<E>: collects multiple errors in sequential or parallel effect executions
• Empty: usually seen as one of the members of Sequential or Parallel when one side succeeded and the other failed

export type Cause<E> = Empty | Fail<E> | Die | Interrupt | Sequential<E> | Parallel<E>

There are multiple APIs in effect to cause, recover, and inspect defects. Some of the most commons are:

• Effect.die
• Effect.interrupt
• Layer.orDie
• Effect.catchAllCause
• Effect.catchAllDefect
• Effect.tapDefect

From a software design standpoint, defect are unrecoverable. Some examples are:

• Out of memory
• Power outage
• Stack overflow

Unlike failures, defects should never be designed as part of a normal flow, and instead you should allow the program to crash.

I encourage you to take a look at them yourself (the API reference is your best friend).