test(tvix/eval): Add proof-of-concept test for Chunk

This is pretty boring at the moment, but mostly serves as a foot in the
door in the direction of writing more tests

Change-Id: Id88eb4ec7e53ebb2d5b5c254c8f45ff750238811
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6637
Autosubmit: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/eval/src/opcode.rs

@@ -5,7 +5,7 @@ use std::ops::{AddAssign, Sub};
 
 /// Index of a constant in the current code chunk.
 #[repr(transparent)]
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct ConstantIdx(pub usize);
 
 /// Index of an instruction in the current code chunk.
@@ -39,17 +39,17 @@ pub struct UpvalueIdx(pub usize);
 
 /// Offset by which an instruction pointer should change in a jump.
 #[repr(transparent)]
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct JumpOffset(pub usize);
 
 /// Provided count for an instruction (could represent e.g. a number
 /// of elements).
 #[repr(transparent)]
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct Count(pub usize);
 
 #[warn(variant_size_differences)]
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum OpCode {
     /// Push a constant onto the stack.
     OpConstant(ConstantIdx),