Need explanation how `context` and `with_context` operate on non-anyhow types about comprehensive-rust HOT 2 CLOSED

Thanks for bringing this up! We don't mention the orphan rule at all, in fact.

This is not a violation of the orphan rule, since the anyhow crate both defines the Context trait and implements it for Option and Result.

But how does rust find the context method? for result in your example? What if some other crate also implemented a trait with a context method that applied to Result? The use anyhow::Context is what signals that this module wishes to use anyhow::Context::context here. That's a bit awkward since it requires useing the trait name, while only the method name appears in the source. I've seen a few people disambiguate this by putting the use statement closer to the method call:

fn main() {
    use anyhow::Context;
    let result = fs::File::open("config.dat");
    print_type_of("result", &result);
    let result_ctx = result.context("Failed to open");
    print_type_of("result_ctx", &result_ctx);
}

but I don't think that is a common approach.

Do you want to make a PR to add some content regarding the orphan rule and this "use trait" syntax?

from comprehensive-rust.

OK, I'll make a PR. Thank you for the explanation!

from comprehensive-rust.