I really like the idea of "sound" programming languages. Elm is a great example of a reasonably simple, very sound programming language that force you to handle all cases (short of a compiler bug, hardware failure, or an explicit fail the world statement, it basically cannot throw exceptions).

Unfortunately the odds of this ending up in a mainstream language this decade is pretty low: the extreme focus on terse code and DRY means the average dev balks at the verbosity (thus the coment in the linked piece of code being necessary). It's a shame, as it's objectively superior by many metrics.