rc-typescript

Use a discriminated union instead of boolean flags: define variants like idle, loading, failed with error, and loaded with data. After checking the status discriminant, the compiler narrows the type so optional chaining and non-null assertions disappear.

Treat response data as unknown, define a Zod schema, and call schema.parse at the boundary so failures throw where context exists. Derive the TypeScript type with z.infer from the schema rather than declaring both separately.

Replace as-casts with parsing at trust boundaries, type narrowing with if checks, or satisfies when you want a value checked without widening its inferred type. The satisfies operator keeps literal keys while validating against a target shape.

Yes, strict: true is the baseline that enforces most type design rules. The noUncheckedIndexedAccess flag adds further safety by typing array index access as T or undefined, reflecting that the element may not exist.

Use branded types when two same-typed values like UserId and OrgId strings could plausibly be swapped and the cost is real. Reserve branding for identifiers, money, and units rather than every string to avoid ceremony.