unused imports should not be fixed from use foo;\n to \n

[samuela]

Right now rustfix fixes unused imports by removing but instead of replacing an unused import use foo;\n with ``, it inserts \n. This gets really annoying when you have a single block of imports and it ends up looking "hole punched":

use crate::archival::libarchive::bb_archive::file_header_t;
use crate::libbb::llist::llist_t;


use crate::librb::bb_uidgid_t;
use crate::librb::fd_pair;
use crate::librb::size_t;
use crate::librb::uoff_t;

use libc;
use libc::close;
use libc::fprintf;
use libc::free;

use libc::gid_t;
use libc::lstat;
use libc::mode_t;
use libc::off_t;
use libc::pid_t;

use libc::printf;
use libc::stat;

use libc::strcpy;
use libc::uid_t;
use libc::FILE;

On its own this wouldn't be that big of a deal but since these have now been split into separate import "blocks" rustfmt will no longer condense them.

[ehuss]

Thanks for the report! I transferred this to rust-lang/rust, as that is where lints and suggestions are implemented.

This is very similar to #51176, and I suspect it will have the same concerns listed in that issue. There are also more details on how to approach that issue at rust-lang/rustfix#158 (comment).