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Thanks for explaining, though since the code is formally correct - taking into account thread joins can't really be considered a special case. I suspect thread

• marcosdumay 4y ago
  Yes, the code is correct. That comes from the undecidability of any interesting property in Turing complete code. It means that if you are doing static analysis on your code, you have to decide if you are going with false errors or mark bad code a correct, because no analysis can always give you the correct result. On this case, you get a false error.
• steveklabnik 4y ago
  It doesn't need to be a language feature. Scoped threads are a library implementation of the idea of joining right away. The issue is that spawn is specifically the most general API; one where you may never even join the thread at all, hence its type signature requiring a 'static bound. Rust doesn't suddenly go "oh you're not actually using the full power this signature gives you, so I'll allow it," because that would make the code extremely fragile, be tough to implement, all sorts of things. Really, this is about using the API that communicates the semantic you want, so that the compiler can check it.