I’ve long wished for an SQL error model: given a schema, query, and transaction isolation mode, what errors are theoretically possible?

I have a hard time answering this for Postgres, which disappoints me because I don’t see any reason it sounds very easy to answer, like there could be an extension to EXPLAIN that would dry run the query and list all the error states reachable.

Computer Science is incredibly immature. Many of its "founding fathers" are still alive!

Something akin to this that blew my mind recently was an IDE for a functional language that used typed holes, the programming equivalent of a semiconductor electron "vacancy", a quasi-particle with real properties that is actually just the lack of a particle. The concept was that if you delete (or haven't yet typed) some small segment out of an otherwise well-typed program, the compiler can figure out the type that the missing part must have. This can be used for rapid development because many such "holes" can only have one possible type.

This kind of mechanistic development with tool assistance is woefully under-developed.