Commutativity doesn't apply to sum types, though it does apply to union types. Here I'm using the type theory terms, not the terms used by OP. So this isn't rea

Commutativity doesn't apply to sum types, though it does apply to union types. Here I'm using the type theory terms, not the terms used by OP. So this isn't really an issue. Zero values don't make any sense anyway. As the original comment said "You might think this is a pretty dumb design decision that can lead to programmer error, but it meshes perfectly with the other mistakes in the language."