Errors Are Values

Every language must answer: what happens when an operation fails? Exceptions answer with a jump — control teleports to the nearest handler, and every function between is silently interruptible. Null answers with a landmine — a value that detonates somewhere far from where it was made.

Crow's answer: failure is data. A failed operation returns a value that knows it failed and can say why. That value flows through your program like any other — until something tries to act on it, at which point Crow refuses to guess. No try, no catch, no null, no unwinding.

You've been using this model since chapter 2. This chapter makes it precise, in four steps: what every value carries, how failures travel, why an error can never decide a branch, and how to handle one on purpose.