feat(tvix/eval): eliminate the only `unsafe` in the codebase r/5129

Maybe I misunderstood this part of the code, but the use of `unsafe`
appears unnecessary here?  In any event it is the one and only
`unsafe` in the codebase.

Hopefully getting to "no `unsafe` anywhere" is worth the extra
never-taken branch caused by unwrap() instead of unwrap_unchecked()?

Signed-off-by: Adam Joseph <adam@westernsemico.com>
Change-Id: I33fbd5aad9d8307ea82c24b6220412783e1973c6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7011
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

1 files changed, 2 insertions, 4 deletions

diff --git a/tvix/eval/src/vm.rs b/tvix/eval/src/vm.rs
index 50dabf1ee8d5..e1f9d3096b89 100644
--- a/tvix/eval/src/vm.rs
+++ b/tvix/eval/src/vm.rs
@@ -741,11 +741,9 @@ impl<'o> VM<'o> {
         // Iterate over the captured with stack if one exists. This is
         // extra tricky to do without a lot of cloning.
         for idx in (0..self.frame().upvalues.with_stack_len()).rev() {
-            // This is safe because having an index here guarantees
+            // This will not panic because having an index here guarantees
             // that the stack is present.
-            let with =
-                unsafe { self.frame().upvalues.with_stack().unwrap_unchecked()[idx].clone() };
-
+            let with = self.frame().upvalues.with_stack().unwrap()[idx].clone();
             if let Value::Thunk(thunk) = &with {
                 fallible!(self, thunk.force(self));
             }