No method iter_chain() is defined for Context<T>

[Vyacheslav Gudkov]

Hi, i am trying to use iter_chain() for Context<T> and compiler says that no such method defined. May be it is because it only exists in impl block of Fail and isn't defined in pub trait statement.

I still can use causes(), but it produces deprecation warning.

Any help with this?

[Armin Ronacher]

Works for me:

extern crate failure;

use failure::Fail;
use std::io;


fn main() {
    let err = io::Error::new(io::ErrorKind::Other, "This is an error");
    let err_with_ctx = err.context("Testing");
    for cause in Fail::iter_chain(&err_with_ctx) {
        println!("{}", cause);
    }
}

[Vyacheslav Gudkov]

But the following will fail

 for cause in err_with_ctx.iter_chain() {
     println!("{}", cause);
 }

It is hard to understand that Fail::iter_chain(&err_with_ctx) form should be used. Very non-usual way to call methods with &self param in rust. Anyway thanks for an example, it solves my problem.

[Armin Ronacher]

Correct. This change was intentionally made because that cannot be supported without creating situations where ambiguity cannot be resolved. I don't know a way around that.

[Raimundo Saona]

Hi there!

Would it be possible to add such an example in the documentation, please?
I also didn't understand it at the beginning.

Thanks beforehand!