4 ms·

What are the cases when `try!` macro bettern than `?` operator? I'm a beginner to Rust so I don't know about that.

• est31 7y ago
  Often when you are getting error messages you would like to find the place they originate. Failure provides backtraces but not everyone uses failure and tbh it's quite a heavy dependency, using serde and so on. With try!, you can easily shadow the macro to e.g. emit a panic. This can be done to basically any codebase using try!, even if it's not yours. Migrating it to use failure is much harder :). It would be cool if you just had a compiler flag that invokes an user settable handler function every time Err() gets constructed or something like that. To give concrete examples, I was developing a library to generate certificates [1]. Often you generate a wrong one though and the parser library you use for testing gives you a Err(BadDer). If that's everything you are getting it can be a bit tough to find out the origins. As it was using ? I had to grep for all the places returning a BadDer error and replace them with a panic. Shadowing try! would have been much easier. [1]: https://github.com/est31/rcgen https://github.com/est31/rcgen
  • lzutao 7y ago
    Thanks through I still don't get it. I only know that you can get backtraces of errors by setting `RUST_BACKTRACE=1`.
    • est31 7y ago
      That only gives you backtraces for panics, but not for errors based on the Result<,> type.
      • lzutao 7y ago
        I am not serious. Often in these cases I would use printf debugging to know where the errors came. (I am still a Rust beginner).