Merge #5142

5142: analysis-stats: allow parallel type inference r=matklad a=jonas-schievink

This is mostly just for testing/fun, but it looks like type inference can be sped up massively with little to no effort (since it runs after the serial phases are already done).

Without `--parallel`:

```
Item Collection: 16.43597698s, 683mb allocated 720mb resident
Inference: 25.429774879s, 1720mb allocated 1781mb resident
Total: 41.865866352s, 1720mb allocated 1781mb resident
```

With `--parallel`:

```
Item Collection: 16.380369815s, 683mb allocated 735mb resident
Parallel Inference: 7.449166445s, 1721mb allocated 1812mb resident
Inference: 143.437157ms, 1721mb allocated 1812mb resident
Total: 23.973303611s, 1721mb allocated 1812mb resident
```

Co-authored-by: Jonas Schievink <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 580add41f..e1d2475e2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1461,6 +1461,7 @@ dependencies = [
  "ra_toolchain",
  "ra_tt",
  "rand",
+ "rayon",
  "rustc-hash",
  "serde",
  "serde_json",