AsyncResult.andThen return type behaves weirdly sometimes

[jstasiak]

TypeScript 5.6.2, ts-results-es 4.2.0.

async function f(x: Result<string, number>) {
    const y1 = x.toAsyncResult()
    const y2 = y1.andThen((value) => Ok('success'))
    const final = await y2.promise
}

final's type is Result<string, unknown> while ideally it should be Result<string, number>.