# Objective
Fixes#18103#17330 introduced a significant compile time performance regression
(affects normal builds, clippy, and Rust Analyzer). While it did fix the
type-resolution bug (and the general approach there is still our best
known solution to the problem that doesn't involve [significant
maintenance
overhead](https://github.com/bevyengine/bevy/issues/18103#issuecomment-2702724676)),
the changes had a couple of issues:
1. It used a Mutex, which poses a significant threat to parallelization.
2. It externalized existing, relatively simple, performance critical
Bevy code to a crate outside of our control. I am not comfortable doing
that for cases like this. Going forward @bevyengine/maintainer-team
should be much stricter about this.
3. There were a number of other areas that introduced complexity and
overhead that I consider unnecessary for our use case. On a case by case
basis, if we encounter a need for more capabilities we can add them (and
weigh them against the cost of doing so).
## Solution
1. I moved us back to our original code as a baseline
2. I selectively ported over the minimal changes required to fix the
type resolution bug
3. I swapped `Mutex<BTreeMap<PathBuf, &'static Mutex<CargoManifest>>>`
for `RwLock<BTreeMap<PathBuf, CargoManifest>>`. Note that I used the
`parking_lot` RwLock because it has a mapping API that enables us to
return mapped guards.
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