Make cargo fix remove unused imports

[hirschenberger]

Describe the problem you are trying to solve

It would be great, if cargo fix could remove unused imports. Import handling is already tedious when using many dependencies without preludes and so it would be great it cargo could automatically remove the superfluous imports.

Describe the solution you'd like

cargo fix and all warning: unused import:... messages are gone.

Notes

Unfortunately rustc does not give a hint, how to get rid of the warning. So one could either handle the fix in cargo itself or extend rustc's warning message.

[alexcrichton]

Thanks for the report! This is covered by rust-lang/rust#50723 in upstream rust-lang/rust as it'll need support from rustc to emit the right fix annotations.

[dwijnand]

Duplicate of #5846

[cjhopman]

@alexcrichton The upstream issue is now closed, but afaict cargo fix still doesn't remove unused imports. Am I missing something?

[cjhopman]

Maybe rust-lang/rust#47888 or rust-lang/rust#53934 cover what remains to support this.