None of my customers ever asked for type definitions in Ruby (nor in Python.) I'm pretty happy of the choice of hiding types under the carpet of a separate file. I think they made it deliberately because Ruby's core team didn't like type definitions but had to cave to the recent fashion. It will swing back but I think that this is a slow pendulum. Talking about myself I picked Ruby 20 years ago exactly because I didn't have to type types so I'm not a fan of the projects you are working at, but I don't even oppose them. I just wish I'm never forced to define types.