export declare function filter<A>(predicateFn: (value: A) => boolean): (option: Option<A>) => Option<A>;

export declare function filter<A, B extends A>(predicateFn: (value: A) => value is B): (xs: Array<A>) => Array<B>;

type WithOrWithoutYou = {type: 'with', you: string} | {type: 'without'};

declare const withOrWithout: WithOrWithoutYou;

pipe(
  O.some(withOrWithout),
  O.filter(w => w.type === 'with'),
  O.map(w => w.you), // <--- Fails with: Property 'you' does not exist on type 'WithOrWithoutYou'.
)