B給A一個新的promise，但A沒有就B的新promise給予對待給

B給A一個新的promise，但A沒有就B的新promise給予對待給付，而是去履行原契約，此時第二個promise就缺乏對價，但其仍為一個債權。此時A沒有請求權，因此若A去履行原契約義務，而依照第二個promise向B請求給付，則其無從請求，但若B願為給付則A仍有權受領

結果 (英文) 1:

B gives A a new promise, but A does not pay for B's new promise, but fulfills the original contract. At this time, the second promise lacks consideration, but it is still a claim. At this time, A has no right to claim. Therefore, if A fulfills the original contract obligations and requests payment from B according to the second promise, he will have no way to request it. However, if B is willing to pay, A still has the right to receive it.

結果 (英文) 2:

B gave A a new promise, but A did not treat B's new promise as payment, but instead fulfilled the original contract. At this point, the second promise lacks consideration, but it is still a debt. At this point, A has no right to request, so if A fulfills its original contractual obligations and requests payment from B according to the second promise, it has no way to request it. However, if B is willing to pay, A still has the right to receive it

結果 (英文) 3:

B gives A a new promise, but A doesn't pay for B's new promise, but performs the original contract. At this time, the second promise lacks consideration, but it is still a creditor's right. At this time, A has no claim, so if A goes to fulfill the original contractual obligations and requests payment from B according to the second promise, it has no request, but if B is willing to pay, A still has the right to receive it.