m05-type-driven

The type state pattern in Rust prevents invalid state transitions by encoding states as distinct types, ensuring that state machine transitions only occur between valid states at compile time. This eliminates accidental misuse.

To make invalid states unrepresentable, apply type-driven design using newtypes, sealed traits, and Zero-Sized Types (ZSTs). This approach enforces data invariants directly within the type system for robust compile-time validation.

Use the newtype pattern for compile-time validation when you need to ensure data integrity by distinguishing primitive values. It wraps primitive types in distinct structs to prevent mixing incompatible data and enforce constraints.

PhantomData and marker traits improve type safety by allowing you to encode compile-time constraints without runtime overhead. They act as logical markers to track ownership or type relationships within the type system.

Yes, the builder pattern combines with sealed traits to enforce invariants by ensuring only valid configurations can be constructed. Sealed traits restrict implementation to the defining crate, securing the builder's state transitions.