Type Alias ExtendBrand<B, T, F>

ExtendBrand: IsNever<F & T> extends true
    ? Brand<
        GetBrandValuePart<B>,
        T | UnwrapBrandTrueKeys<B> & string,
        F | UnwrapBrandFalseKeys<B> & string,
    >
    : never

Extends an existing brand with additional true/false keys. Fails if the same key would be marked as both true and false.

Type Parameters

B extends UnknownBrand
The base brand to extend
T extends string
Additional keys to mark as true
F extends string = never
Additional keys to mark as false (defaults to never)

Returns

Extended brand type, or never if T and F have common keys

Example

type Email = Brand<string, 'email'>;
type ValidatedEmail = ExtendBrand<Email, 'validated'>;
// ValidatedEmail has both 'email' and 'validated' as true

type OptionalEmail = ExtendBrand<Email, 'optional', 'required'>;
// Has 'email' and 'optional' as true, 'required' as false

// This would return never (conflicting keys):
// type Invalid = ExtendBrand<Email, 'verified', 'verified'>;