>
> I think using promises as tokens would be problematic. It would have
> several issues:
>
Agreed with all of those.
It's also important to keep in mind that promises can be subclassed so it's
> fine to add properties to them if used for a specific purpose like
> cancellation.
>
We could use a promise subclass as the cancellation token, but then tokens
(and their constructor) would inherit things that really don't make sense,
like "CancelToken.resolve" and "CancelToken.prototype.catch".
On the other hand, it doesn't really make sense to create a new callback
API (`whenCancelled`), when we already have the necessary callback
semantics with promises. Perhaps we can expose a promise on the token
instead:
class CancelToken {
get requested() : bool;
get promise() : Promise;
throwIfRequested() : void;
}
// Registering a callback
token.promise.then(_=> doSomething());
// Doing other things with the promise
Promise.race(token.promise, someOtherPromise);
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