Use the same deprecation macros on the no_std Error as the official Error

[NWPlayer123]

While writing up documentation, I noticed several deprecation warnings concerning description and cause, which have been deprecated since March 2020 and February 2019 respectively, which are coming up on 4 and 5 years ago, so I think it's high time to remove them entirely. Any repositories that still rely on it can either fix to a specific older version, or update their code to remove it.

[shepmaster]

If I create an error type not using SNAFU and check its documentation, it contains those deprecation warnings:

use std::fmt;

#[derive(Debug)]
pub struct Demo;

impl fmt::Display for Demo {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        "Demo".fmt(f)
    }
}

impl std::error::Error for Demo {}

I'm sure you've checked something similar, so I'm not sure I understand what your end goal is here. Can you try and restate so I understand better?

[NWPlayer123]

So it does, interesting. I was mostly bringing this up because I found https://github.com/shepmaster/snafu/blob/main/src/no_std_error.rs#L6 as I was digging around how no_std works, and that's what I was mostly taking issue with.

In that case, you should use the same deprecation macro as the official Error does, as library authors are able to use it.

[shepmaster]

around how no_std works

If possible for your case, I'd recommend that you use the unstable-core-error feature flag to use the version of Error that lives in the core library. Once that is stable enough, SNAFU will no longer have a reason to create its own Error trait.