[pron]

> I think people "overblow" the color problem of the Async API too much. If most things are async it isn't really that painful.

There are two problems with async/await's cooperative multitasking:

1. The first is only relevant to languages that also have threads: it splits the APIs into two worlds with very similar semantics but disjoint syntactic "universes." You always need a separate API for either world and need to do everything twice.

2. Even when that is the only paradigm, it is less composable. When scheduling points are explicit, adding a scheduling point inside a subroutine requires changing all of its callers, transitively. In contrast, with non-cooperative multitasking, any subroutine in the hierarchy can individually choose to exclude interleaving (and in a finer-grained way) for atomic operations with various constructs (the simplest being locks). Since most operations need not be atomic and are independent, this is not only more composable and evolvable, but also a more reasonable default.