feat(tvix/eval): Forbid Hash{Map,Set}, use Fx instead r/8453

Per https://nnethercote.github.io/perf-book/hashing.html, we have
basically no reason to use the default hasher over a faster,
non-DoS-resistant hasher. This gives a nice perf boost basically for
free:

hello outpath           time:   [704.76 ms 714.91 ms 725.63 ms]
                        change: [-7.2391% -6.1018% -4.9189%] (p = 0.00 < 0.05)
                        Performance has improved.

Change-Id: If5587f444ed3af69f8af4eead6af3ea303b4ae68
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12046
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Reviewed-by: Ilan Joselevich <personal@ilanjoselevich.com>
Autosubmit: aspen <root@gws.fyi>

1 files changed, 3 insertions, 5 deletions

diff --git a/tvix/eval/src/compiler/scope.rs b/tvix/eval/src/compiler/scope.rs
index 7b0a66004a7f..1087e0153e42 100644
--- a/tvix/eval/src/compiler/scope.rs
+++ b/tvix/eval/src/compiler/scope.rs
@@ -10,10 +10,8 @@
 //! stack indices. To do this, the compiler simulates where locals
 //! will be at runtime using the data structures implemented here.
 
-use std::{
-    collections::{hash_map, HashMap},
-    ops::Index,
-};
+use rustc_hash::FxHashMap;
+use std::{collections::hash_map, ops::Index};
 
 use smol_str::SmolStr;
 
@@ -168,7 +166,7 @@ pub struct Scope {
     pub upvalues: Vec<Upvalue>,
 
     /// Secondary by-name index over locals.
-    by_name: HashMap<String, ByName>,
+    by_name: FxHashMap<String, ByName>,
 
     /// How many scopes "deep" are these locals?
     scope_depth: usize,