My problem with promises is that you can't "uninvoke" them. I.e., if all listeners unsubscribe, the original job they were waiting for could be killed, but the design of Promises doesn't allow that. Instead, the job will continue to be executed (without any listeners), and thus wasting resources.
I won't argue that sometimes you might want to cancel a promise that you no longer need (ex: user cancels ajax operation) but just because there are no listeners does not always mean you don't want it to complete (ex: Fire and forget, not always a great idea sure but a thing nonetheless).
I think it's less of a design flaw and more a conceptual issue. Since a Promise is just a value, it can be stored in an arbitrary data structure on the heap with no listeners. But the then() method can be called any time later. So, a promise being potentially "listened to" is really just being reachable by the garbage collector.
There's no reason the source of the promise can't implement a cancel() method, though.
Why are you generating the promise in the first place if there are no listeners? Why don't you return a function which can be used to generate the promise instead?
