Tracking issue for RFC 2504, "Fix the Error trait"

[Centril]

This is a tracking issue for the RFC "Fix the Error trait" (rust-lang/rfcs#2504).

Steps:

• Implement the RFC (cc @rust-lang/libs)
  • source method #53533
  • Backtrace API
• Adjust documentation (see instructions on forge)
• Stabilization PR (see instructions on forge)

Unresolved questions:

• The choice to implement nullability internal to backtrace may prove to be a mistake: during the period when backtrace APIs are only available on nightly, we will gain more experience and possible change backtrace's constructors to return an Option<Backtrace> instead.

[Laaas]

What parts haven't been implemented?

[withoutboats]

I've updated the tracking issue to reflect that, but right now the source method has been implemented, but the backtrace related APIs have not been implemented

[Laaas]

Perhaps I could try implementing this, is it OK to just use the backtrace crate?

[alexcrichton]

Implementing backtraces in the standard library will probably not use the backtrace crate but rather the backtrace API that's already in the standard library for RUST_BACKTRACE. We can perhaps unify these implementations in the long run, but for now it's infeasible to do so.

The current platform-independent backtrace code lives here, mostly in the _print function. Implementing the API defined in the RFC will likely involve reusing these interfaces to define a struct which carries along the relevant information.

@Laaas if you'd like to implement this please feel free! Also feel free to reach out with any questions.

[Laaas]

Thanks! Will definitely try implementing it.

[frewsxcv]

Thanks! Will definitely try implementing it.

@Laaas Did you make any progress? Need any help?

[Laaas]

@frewsxcv Actually not!

I haven't really looked at it much, so if you want to work on it, go ahead!

[aturon]

cc @rust-lang/libs @withoutboats @mitsuhiko would be really nice to make progress here

[mitsuhiko]

I would move than love to spearhead this.

[aturon]

@mitsuhiko go go go! if you need any help around the backtrace stuff @alexcrichton can get you set up.