Comment by rscho

No, it will get in the way more than anything else. As has been said elsewhere in thread, what we need to ensure in R is mostly runtime constraints (array shape, number in specific interval, etc.) this would require a super heavy and complex type system, with at least refinement and probably fully-dependent types. It would be too complex to use for most people and use cases. A contract system would be far more practical and useful. See CHECK and other constraints in SQLite. That's exactly what we need.