Depends on the type of code you’re writing. If your `switch` is tightly coupled to the code that defines the cases and they’ll definitely be changed in lockstep

Depends on the type of code you’re writing. If your `switch` is tightly coupled to the code that defines the cases and they’ll definitely be changed in lockstep, a default is more likely to be harmful. If your cases are defined externally, and you need to be forwards compatible, omitting a default is wrong. The Swift language specifically added `@unknown default` for switching over enums.