Self Modifying Type Predicates in Typescript
TypeScript’s type predicates can modify the type of this itself, enabling self-modifying type behavior that approaches dependent types. By implementing is<K extends keyof ShapeTypes>(type: K): this is ShapeTypes[K] on abstract classes, we achieve compile-time type narrowing where shape.is('circle') transforms the shape variable’s type from Shape to Circle, unlocking properties like shape.radius within conditional blocks.