feat: WIP

evaluator/nixjit_context/src/downgrade.rs

@@ -22,10 +22,15 @@ impl<'ctx, 'bump> DowngradeCtx<'ctx, 'bump> {
 
 impl DowngradeCtx<'_, '_> {
     fn get_ir(&self, id: ExprId) -> &RefCell<Hir> {
+        // SAFETY: The `ExprId` is guaranteed to be valid and correspond to an expression
+        // allocated within this context, making the raw index access safe.
         let idx = unsafe { id.raw() } - self.ctx.lirs.len() - self.ctx.hirs.len();
         if cfg!(debug_assertions) {
             self.irs.get(idx).unwrap()
         } else {
+            // SAFETY: The index calculation is guarded by the logic that creates `ExprId`s,
+            // ensuring it's always within the bounds of the `irs` vector in release builds.
+            // The debug build's `unwrap()` serves as a runtime check for this invariant.
             unsafe { self.irs.get_unchecked(idx) }
         }
     }