from Soutarowho who did the type system for Ruby 3:
We defined a new language called RBS for type signatures for Ruby 3. The signatures are written in .rbs files which is different from Ruby code. You can consider the .rbs files are similar to .d.ts files in TypeScript or .h files in C/C++/ObjC. The benefit of having different files is it doesn't require changing Ruby code to start type checking. You can opt-in type checking safely without changing any part of your workflow.[1]
So UX-wise I don't know. While it's nice to have them separated, you are just faster if you have types in the code in front of your face when the IDE warns. Otherwise you will context-switch on any warning/error. This could get significant since you code just based on the LSP's output sometimes for hours. The IDE could help here with showing the definition when warning but still, if you want to change the definition or want to see more than just a snippet you will constantly jump between files.
Also .d.ts files were introduced to type old code and as an fallback and as a secondary option, At some point, Matz and Soutaro need to integrate types into the language itself to get the same level of productivity other typed languages offer, eg. Rust/Go/TS.
We defined a new language called RBS for type signatures for Ruby 3. The signatures are written in .rbs files which is different from Ruby code. You can consider the .rbs files are similar to .d.ts files in TypeScript or .h files in C/C++/ObjC. The benefit of having different files is it doesn't require changing Ruby code to start type checking. You can opt-in type checking safely without changing any part of your workflow.[1]
So UX-wise I don't know. While it's nice to have them separated, you are just faster if you have types in the code in front of your face when the IDE warns. Otherwise you will context-switch on any warning/error. This could get significant since you code just based on the LSP's output sometimes for hours. The IDE could help here with showing the definition when warning but still, if you want to change the definition or want to see more than just a snippet you will constantly jump between files.
Also .d.ts files were introduced to type old code and as an fallback and as a secondary option, At some point, Matz and Soutaro need to integrate types into the language itself to get the same level of productivity other typed languages offer, eg. Rust/Go/TS.
The next thing is IDE support, anyone knows more?
[1] https://developer.squareup.com/blog/the-state-of-ruby-3-typi...