feat: TODO

evaluator/nixjit_context/src/downgrade.rs

@@ -43,6 +43,12 @@ impl DowngradeContext for DowngradeCtx<'_, '_> {
     }
 
     fn with_expr_mut<T>(&mut self, id: ExprId, f: impl FnOnce(&mut Hir, &mut Self) -> T) -> T {
+        // SAFETY: This is a common pattern to temporarily bypass the borrow checker.
+        // We are creating a mutable reference to `self` from a raw pointer. This is safe
+        // because `self_mut` is only used within the closure `f`, and we are careful
+        // not to create aliasing mutable references. The `RefCell`'s runtime borrow
+        // checking further ensures that we don't have multiple mutable borrows of the
+        // same `Hir` expression simultaneously.
         unsafe {
             let self_mut = &mut *(self as *mut Self);
             f(&mut self.get_ir(id).borrow_mut(), self_mut)
@@ -57,6 +63,10 @@ impl DowngradeContext for DowngradeCtx<'_, '_> {
         for (idx, ir) in self.ctx.hirs.iter().enumerate() {
             println!(
                 "{:?} {:#?}",
+                // SAFETY: The index `idx` is obtained from iterating over `self.ctx.hirs`,
+                // so it is guaranteed to be a valid index. The length of `lirs` is added
+                // as an offset to ensure the `ExprId` correctly corresponds to its position
+                // in the combined IR storage.
                 unsafe { ExprId::from_raw(idx + self.ctx.lirs.len()) },
                 &ir
             );