When "use" lines are re-arranged, inline comments are placed on the wrong line

[Teknomancer]

Describe the bug

When use lines are re-arranged by the formatter, comments are moved to the wrong line.

To Reproduce

1. cargo new hello_world --bin
2. cd hello_world
3. Edit src/main.rs to have these exact lines (order of lines is important)

use std::convert::TryFrom;
use std::fmt;
use std::collections::{Vec, VecDeque};  // testing

fn main() {
    println!("Hello, world!");
}

4. cargo fmt
5. Check src/main.rs, the //testing comment has been moved from std::collections line to std::fmt line as shown below:

use std::collections::{Vec, VecDeque};
use std::convert::TryFrom;
use std::fmt; // testing

fn main() {
    println!("Hello, world!");
}

Expected behavior

The comments in use lines should stay with the same line when lines are re-arranged (I'm assuming it's done in alphabetical order). In the above example it would be:

use std::collections::{Vec, VecDeque};  // testing
use std::convert::TryFrom;
use std::fmt;

Meta

• rustfmt version: rustfmt 1.4.25-stable (0f29ff6d 2020-11-11)
• From where did you install rustfmt?: rustup component add rustfmt
• How do you run rustfmt: cargo-fmt

I'm running this on Windows 10 (64-bit) host.

[calebcartwright]

Closing as duplicate of #4027/#3720