The current MemoryLayout implementation has many good properties.

However, there are some improvement areas:

1) It is desirable to allow "patterns in switch statement". It is not possible to obtain totality (other than trivially using default or MemoryLayout itself).
2) It is desirable to remove the AbstractLayout from the API. Even though this class is package private, it would be a benefit to completely hide its functionality.
3) it is desirable to generally reduce the public API (various permitted concrete implementations are visible in the public API)