inconsistent imports sorting when merging imports

[antonilol]

Summary

I had this code:

use super::Enum;
use super::Struct;
use super::module::Trait;

Then I merged the imports on the first two lines into this:

use super::{Enum, Struct};
use super::module::Trait;

rustfmt then swapped the lines:

use super::module::Trait;
use super::{Enum, Struct};

Expected behavior

I expected to see this happen: imports of items from super stay at the top

Actual behavior

Instead, this happened: imports from super::module get sorted above items from super

Configuration

rustfmt cli options used (if applicable):

$ rustfmt main.rs --edition 2024

rustfmt configuration file (e.g. rustfmt.toml, if applicable): n/a

Reproduction Steps

See summary

Meta

rustfmt --version:

rustfmt 1.8.0-stable (4a4ef493e3 2026-03-02)

It can be more cleary seen with this code:

use super::CONSTANT;
use super::module::Trait;
use super::{Enum, Struct};

The merged imports are put below use super::module ..., normal imports like use super::CONSTANT here is correctly put at the top.

[ytmimi]

Confirmed the behavior with rustfmt 1.9.0-nightly (20a50e4 2026-03-12).

I don't think the edition has anything to do with this. In order to address this we will likely need to make changes to the Ord impl for UseTree.