Type Alias EmitFn<Options, Event, ReturnType>

EmitFn: Options extends (infer V)[]
    ? (event: V, ...args: any[]) => ReturnType
    : {} extends Options
        ? (event: string, ...args: any[]) => ReturnType
        : UnionToIntersection<
            {
                [key in Event]: Options[key] extends (...args: infer Args) => any
                    ? (event: key, ...args: Args) => ReturnType
                    : (event: key, ...args: any[]) => ReturnType
            }[Event],
        >