Function save_and_restore_depth_basic

crates/kernel/src/tc.rs:1466–1475

()

    tc.push_local(var(3));
    tc.push_local(sort1());
    let t = tc.lookup_var(1).unwrap();
    // Lifted from Var(3) with lift-by-(idx+1)=2 → Var(3+2)=Var(5).
    // The implementation calls `lift(&intern, &ty, idx + 1, 0)` which
    // shifts all free bvars by idx+1.
    match t.data() {
      ExprData::Var(i, _, _) => assert_eq!(*i, 5),
      other => panic!("expected Var, got {other:?}"),
    }
  }

  #[test]
  fn lookup_let_val_returns_none_for_lambda_binding() {
    let mut tc = new_tc();