This looks really impressive. I'm curious what the story is around propagating errors through chains of futures. Traditionally future libraries don't pay much a

This looks really impressive. I'm curious what the story is around propagating errors through chains of futures. Traditionally future libraries don't pay much attention to that which can make debugging excruciating, which it doesn't have to be. But then rust does errors differently so maybe it's less of an issue there? About the naming though, I was a little disappointed. Out of future, deferred, and promise, "promise" is the better term. The two others imply that something will happen later which is misleading because it's fine to have promises stick around long after they're fulfilled.