enum-driven-state-refactoring

To refactor optional fields into a discriminated union, you transform ambiguous optional-based state representations into strict, type-safe sum types. This ensures illegal states are structurally impossible by creating distinct variants like `Loading`, `Success`, and `Error`.

The best way to eliminate invalid states with sum types is by replacing parallel booleans and optional fields with strict enums or sealed classes. This approach makes illegal states unrepresentable at compile time, preventing runtime errors and reducing the need for manual validation.

You should use pattern matching over conditional checks when a field's validity is dependent on another field's value. Refactoring loose state models into strict sum types promotes pattern matching, ensuring type safety and preventing invalid state combinations.

To convert parallel booleans to type-safe enums, you refactor the overlapping true/false combinations into distinct variants within a sealed class or discriminated union. This makes invalid state combinations structurally impossible to represent.

Yes, refactoring to sealed classes prevents runtime errors by making illegal states unrepresentable at compile time. By replacing optional fields with strict sum types, the compiler enforces pattern matching exhaustiveness, eliminating invalid state combinations.

Yes, you can refactor a TypeScript interface state model into a strict sum type by transforming optional fields like `data?` and `error?` into distinct discriminated union variants. This ensures the state model is type-safe and illegal states are structurally impossible.