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, 5 insertions, 5 deletions

diff --git a/tvix/eval/src/lib.rs b/tvix/eval/src/lib.rs
index a53a2a02d140..6897e1dd494f 100644
--- a/tvix/eval/src/lib.rs
+++ b/tvix/eval/src/lib.rs
@@ -36,7 +36,7 @@ mod test_utils;
 #[cfg(test)]
 mod tests;
 
-use std::collections::HashMap;
+use rustc_hash::FxHashMap;
 use std::path::PathBuf;
 use std::rc::Rc;
 use std::str::FromStr;
@@ -86,7 +86,7 @@ enum BuilderGlobals {
 pub struct EvaluationBuilder<'co, 'ro, 'env, IO> {
     source_map: Option<SourceCode>,
     globals: BuilderGlobals,
-    env: Option<&'env HashMap<SmolStr, Value>>,
+    env: Option<&'env FxHashMap<SmolStr, Value>>,
     io_handle: IO,
     enable_import: bool,
     strict: bool,
@@ -264,7 +264,7 @@ impl<'co, 'ro, 'env, IO> EvaluationBuilder<'co, 'ro, 'env, IO> {
         Self { nix_path, ..self }
     }
 
-    pub fn env(self, env: Option<&'env HashMap<SmolStr, Value>>) -> Self {
+    pub fn env(self, env: Option<&'env FxHashMap<SmolStr, Value>>) -> Self {
         Self { env, ..self }
     }
 
@@ -352,7 +352,7 @@ pub struct Evaluation<'co, 'ro, 'env, IO> {
     globals: Rc<GlobalsMap>,
 
     /// Top-level variables to define in the evaluation
-    env: Option<&'env HashMap<SmolStr, Value>>,
+    env: Option<&'env FxHashMap<SmolStr, Value>>,
 
     /// Implementation of file-IO to use during evaluation, e.g. for
     /// impure builtins.
@@ -570,7 +570,7 @@ fn parse_compile_internal(
     location: Option<PathBuf>,
     source: SourceCode,
     globals: Rc<GlobalsMap>,
-    env: Option<&HashMap<SmolStr, Value>>,
+    env: Option<&FxHashMap<SmolStr, Value>>,
     compiler_observer: &mut dyn CompilerObserver,
 ) -> Option<Rc<Lambda>> {
     let parsed = rnix::ast::Root::parse(code);