import * as v from 'valibot';
(() => {
  let d = v.intersect([v.object({ a: v.number() }), v.optional(v.object({ b: v.number() }))]);
  console.log();
  type D = v.InferInput<typeof d>;
  type DD =
    | {
        a: number;
      }
    | ({
        a: number;
      } & {
        b: number;
      });

  let d0: D = { a: 1 };
  let d1: DD = { a: 1 };
})();

I know this question was answered before, {}&({}|undefined)=>{}

However, I suddenly came up with the idea yesterday whether it's possible to implement it according to the above DD type. Although this approach might not conform to TypeScript's type system design, it aligns with a person's intuitive sense.

I’m not sure if this design aligns with your vision. If you don't have time to implement it, I can also try to implement it (if feasible)