[0] https://en.wikipedia.org/wiki/Substructural_type_system
https://en.wikibooks.org/wiki/Ada_Programming/Types/access
More importantly the previous discussion on Ada SPARK 2014 'safe pointers' may also be an interesting read for proponents of a Substructural Type System:
https://news.ycombinator.com/item?id=15874273
[0] https://en.wikipedia.org/wiki/Substructural_type_system