message: Delete out of date comments
  Summary: These optimisations have either been done, or don't make sense in the new representation.
diff: * limitations under the License.
  */
  -// Possible optimisations:
  -// Preallocate int, none, bool etc slots in Value, so they are shared
  -// Encoding none, bool etc in the pointer of frozen value
  -
  use crate::{
  collections::Hashed,
  values::{
  