m05-type-driven

Encoding Rust invariants at compile time is achieved by using type-driven design patterns like type state, newtypes, and PhantomData to structurally prevent invalid states. This skill guides you through implementing these zero-cost abstractions for robust API design.

The type state pattern in Rust models state transitions at compile time, ensuring only valid transitions are allowed. Use it when designing state machines or safe abstractions to prevent misuse by making invalid states unrepresentable.

Implement a type-safe builder pattern in Rust by using PhantomData and type state to track required fields at compile time. This skill provides examples of builders and validated constructors that enforce invariants during object creation.

No, you do not need external crates to use PhantomData and sealed traits. This skill requires only stable Rust tooling and standard library constructs to implement zero-sized types and sealed traits, preventing misuse without adding dependencies.

The best way to prevent implementation detail leakage in Rust APIs is by using sealed traits and zero-sized types. This skill covers how to apply these patterns to restrict trait implementations and hide internal types from external consumers.

To create a type-safe newtype wrapper in Rust, define a struct around a primitive type to enforce domain invariants. This skill demonstrates building a type-safe UserId newtype and a simple Connection state machine as practical examples.