> there isn't a clean way to make 'unit types' (second, millisecond, meters, etc) in Rust..

Actually, there's this bit on Tuple Structs[1] in the tutorial:

> Types like this can be useful to differentiate between data that have the same underlying type but must be used in different ways.

  struct Inches(int);
  struct Centimeters(int);

[1] http://static.rust-lang.org/doc/master/tutorial.html#tuple-s...