A module functor is nothing more than a higher order module...one that takes as a parameter some data structure that conforms to an interface (signature). Rust may not have constructs called module functors, but it definitely has constructs that are capably equivalent, as well as some that are even more powerful (a claim that applies to Scala as well)

For me, type inference, strong typing, and ADTs with pattern matching puts a language into the ML family quite easily.