The previous way of sending from the thread pool suffered from stale
diagnostics due to being canceled before we could clear the old ones.
The key change is moving to sending diagnostics from the main loop
thread, but doing all the hard work in the thread pool. This should
provide the best of both worlds, with little to no of the downsides.
This should hopefully fix a lot of issues, but we'll need testing in
each individual issue to be sure.
@matklad mentioned this might be a good idea.
So the general idea is that we don't really need the lock, as we can
just clone the check watcher state when creating a snapshot. We can then
use `Arc::get_mut` to get mutable access to the state from `WorldState`
when needed.
Running with this it seems to improve responsiveness a bit while cargo
is running, but I have no hard numbers to prove it. In any case, a
serialization point less is always better when we're trying to be
responsive.
2681: cargo-watcher: Resolve macro call site in more cases r=matklad a=kiljacken
This resolves the actual macro call site in a few more cases, f.x. when a macro invokes `compile_error!` (I'm looking at you `ra_hir_def::path::__path`).
Co-authored-by: Emil Lauridsen <mine809@gmail.com>
