`graphics::character::CharacterCache>::Error` doesn't require `Debug` trait

[golergka]

I tried to use expect method on the result of CharacterCache.character method, but turns out I can't, because the associated Error type doesn't require Debug trait:

error[E0599]: no method named `expect` found for type `std::result::Result<graphics::character::Character<'_, <G as graphics::Graphics>::Texture>, <C as graphics::character::CharacterCache>::Error>` in the current scope
  --> src/some_file.rs:44:53
   |
44 |             let ch_glyph = glyphs.character(34, ch).expect("Couldn't load character");
   |                                                     ^^^^^^
   |
   = note: the method `expect` exists but the following trait bounds were not satisfied:
           `<C as graphics::character::CharacterCache>::Error : std::fmt::Debug`

It would be obvious to add a constraint that Error should implement the Debug trait. It seems to me as a good idea — however, I'm not sure of it, since I have modest Rust experience. I even asked a question on stack overflow about this pattern.

Anyway, if you guys think it's a good idea, it seems kind of obvious to add the derive to all of it's implementations and I would be glad to do it.

[bvssvni]

You can use map_err? https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.map_err

[golergka]

That's what I'm doing in the meanwhile in my own code, yes. However, I wanted not only to make my own hobby project, but contribute to Piston as well — and this seems like a pretty small thing that I can easily implement. I just need your blessing first :)

Or, if you think that it's a bad idea, I'm not really in position to argue — I don't consider myself to know Rust well enough. But I would really appreciate the explanation, because it would educate me on what's a good and bad practice in Rust.

[bvssvni]

Thanks for the feedback! I checked OpenGL/Gfx/Glium/WGPU/Graphics-Buffer backends and they all use Debug. I think it will not produce too much trouble to require the Debug trait.

[bvssvni]

I think it is a good idea to support this for texture operations too, so I will update piston-texture first.