TypeScript

utils.d.ts

// Brand<number, "USD">
type __BrandWitnes<B= unknown>= Partial<Record<'__witness__',B>>;
type Brand<Base= any, Branding= any, ReservedName extends PropertyKey= '__type__'>
    = Base & Partial<Record<ReservedName,Branding>> & __BrandWitnes<Base>;
// BrandBase<Brand<number, "USD">>
type BrandBase<T extends __BrandWitnes>
    = T['__witness__'];
// tuRecord<"a"|"b","A"|"B","a"> => { a?: "A"|"B", b: "A"|"B" }
type tuRecord<Keys extends PropertyKey, Values, KeysOptional extends PropertyKey= never>
    = Required<Omit<Record<Keys,Values>,KeysOptional>>
    & Partial<Record<KeysOptional, Values>>;


/* imperative
type tuRecord<Keys extends PropertyKey, Values, Optional extends PropertyKey= never>
    = { [K in Exclude<Keys,Optional>]: Values } & { [J in Optional]?: Values };
 */

https://github.com/piotrwitek/utility-types