[mathetic]

My bad, sorry =)

The share from this story is that we can enforce privacy just as we enforce more traditional types at no runtime cost. It scales because it is compositional and compiler can guide us through programs that won't leak data.

A more niche outcome is that Haskell's traditional type system is rich enough to encode this privacy enforcing type system.

I think if you just ignore the syntax, you can still gain a good intuition about how data might leak in subtle ways and what is sufficient to prevent it.