Have you ever seen a code comment saying “this should never happen”? What would happen if it did? Swift has a diverse set of error-handling capabilities, from using throw to send errors up the stack to using a Result to handle errors in asynchronous methods. In this talk, Jeff Kelley will look at the landscape of handling errors in Swift, create new ways of expressing and handling them, and show how even the most impossible code-level situations can have 100% test coverage. You'll walk away with knowledge to take control of the errors in your code.