test: Add assertion in eval_state::tests::eval_state_apply

(cherry picked from commit f8ff14274b6f7accf987328928186b25f842071f)

rust/nix-expr/src/eval_state.rs

@@ -877,6 +877,8 @@ mod tests {
             let v = es.new_value_apply(&f, &a).unwrap();
             assert!(es.value_is_thunk(&v));
             es.force(&v).unwrap();
+            let t = es.value_type(&v).unwrap();
+            assert!(t == ValueType::Int);
             let i = es.require_int(&v).unwrap();
             assert!(i == 3);
         })