Agreed. Another situation where type keys aren’t the grinch is de/serialisation. A contrived example: it’s somewhat simple to imagine the first example as half

Agreed. Another situation where type keys aren’t the grinch is de/serialisation. A contrived example: it’s somewhat simple to imagine the first example as half of a request handler, taking in some string input, asserting it’s within the set of type keys, then acting on it. Later examples, not so much. IMO a great example of “don’t let the perfect be the enemy of the good”