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0 pointsrspeer8y ago0 comments

Sorry, I'm trying very hard to learn Rust, and I'm willing to accept a lot of its restrictions, but this didn't clear anything up.

Why does every library implement its own Error type? It feels like reinventing the wheel, and it takes a lot of boilerplate code.

If you need to distinguish different kinds of errors, why not, for example, have a lot of useful pre-defined error types like Python does?

0 comments

Rusky8y ago

You can definitely reuse other library's error types. I often do that while prototyping.

The benefit of lib-specific error types, though, is that they can be far more specific.

burntsushi8y ago

As an example of the kind of specificity you might want, take a look at the error type for parsing a regular expression: https://docs.rs/regex-syntax/0.4.0/regex_syntax/enum.ErrorKi...

Now, in most cases, callers don't care at all about which specific error happened. They just want to print the error and be done with it. And that works just fine, because of the error handling machinery. But if you do want to drill down, then the option is there for you.

leshow8y ago

You can use pre defined error types. Have you seen https://doc.rust-lang.org/std/io/enum.ErrorKind.html ?

rspeerOP8y ago

That seems to just be kinds of IO errors, though.

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