Consider example of multiple dispatch with intersect(x, y)

[DavisVaughan]

Could be added to this section
https://rconsortium.github.io/S7/articles/generics-methods.html#multiple-dispatch

See also this thread
https://fosstodon.org/@jonocarroll/112913640978442903

intersect(x, y) is not a generic function in base R. We introduced the {generics} R package to turn it into a generic, so we could write methods on them in classes throughout the tidyverse - but the generic only dispatches on x and then it is up to the method to ensure that y is the right class.

It might be interesting to implement intersect(x, y) using multiple dispatch as a motivating example for that feature. I imagine that 99.99% of the time, you will end up only implementing a method for the case where x and y are the same type, i.e. for when they are both Date. But being able to express this in the type system rather than having the method confirm that y is the right type seems nice.