pyrefly

For a one-line/no-code update this unlocks a _lot_ of extra speed/parallelism 😄 Example: and now type-check ~35% faster on my machine 🚀 I think this _might_ also positively impact #3993 by reducing syscalls (these are likely not a big contributor though), so would be marginally additive to https://github.com/facebook/pyrefly/pull/3994. Summary Overview Profiling across the corpus showed syscalls eating a surprising amount of CPU. The trait delegates to the crate, which calls on every , even for already-absolute paths. A project absolutizes once per module (plus per glob/config site), so a large one can issue thousands of unnecessary syscalls per run. This is especially damaging under parallelism: is a process-global syscall that contends across threads, so the cost/impact grows with thread count. Solution Enabling 's "once_cell_cache" feature resolves the just once, via a thread-safe cell, and reuses it. _This completely eliminates the parallel contention without touching any code_. Test Plan No type-checking logic (or actual code!) was changed. All test results are identical before/after. Benchmarks[^1] Timed single-threaded and multithreaded . Tested across ~60 of the projects. = how many modules are in the project. = pyrefly on main branch. = main + this PR. Results below omit trivially-sized or very fast running-projects. Time in seconds, min of 4 runs after warmup. [^1]: Test machine: Apple Silicon M3 Max.

Summary Fixes #4018 Test Plan Regression test added

Summary Fixes #4005 added augmented-assignment operator-region detection and definition/type lookup for +=. wired augmented-assignment operator type lookup into hover. Test Plan added regression coverage for hover and verified RHS literal hover is preserved.