Sometimes there's only one possible function of a given typing.
For example, if a function's type is `a -> b -> (a, b)`, there's really only one function fitting that shape: cons. What else could a (pure) function possibly do, with that typing, other than "exactly what cons does"?
For example, if a function's type is `a -> b -> (a, b)`, there's really only one function fitting that shape: cons. What else could a (pure) function possibly do, with that typing, other than "exactly what cons does"?