cargo fix renames unused local variables from foo to _foo

[MaikKlein]

For example:

let device = &self.ctx.device;
let _device = &self.ctx.device;

I don't like that refactor because I might end up with local variables that do nothing. I think cargo fix should just ignore unused local variables all together. If cargo fix just renames local variables to hide the warnings from the compiler, then the compiler lint is a bit pointless.

Renaming unused function parameters seems fine.

[alexcrichton]

Thanks for the report! I think this may be best reported at rust-lang/rust though where the fix would live. Mind reopening the issue over there?

[MaikKlein]

@alexcrichton Sure no problem, I created a new issue rust-lang/rust#54196