Yeah, I think it's pretty rare to actually need a "local" type as opposed to just making it private to a module in Rust as well. The use case the article gives is one of the few where it I could see it being useful; if you're using a macro in the body of a function and want it to generate a type, there's not anywhere else you can define it (without an additional macro invocation outside the function, which often defeats the purpose of trying to wrap up all the boilerplate into one concise place).