Lifetime hygiene comments missing `#N` suffix in `-Zunpretty=expanded,hygiene` output

[aytey]

I tried the following code (based on this test file):

#![feature(decl_macro)]

macro lifetime_hygiene($f:ident<$a:lifetime>) {
    #[allow(unused_lifetimes, dead_code)]
    fn $f<$a, 'a>() {
        let _: &'_ () = &();
        let _: &'static str = "";
    }
}

lifetime_hygiene!(f<'a>);

and wanted to expand the file with -Zunpretty=expanded,hygiene.

Steps to Reproduce

1. Save the code above to a file (e.g., test.rs)
2. Run rustc -Zunpretty=expanded,hygiene test.rs
3. Observe the output

Expected Behavior

#[allow /* 370#4 */(unused_lifetimes, dead_code)]
fn f /* 917#0 */<'a /* 2538#0 */, 'a /* 2538#1 */>() {
    let _: &'_ /* 56 */ () = &();
    let _: &'static /* 55 */ str /* 2104#4 */ = "";
}

The two lifetimes called 'a would have "hygiene comments" making it clear these were different lifetimes (to the compiler).

Actual Behavior

#[allow /* 370#4 */(unused_lifetimes, dead_code)]
fn f /* 917#0 */<'a /* 2538 */, 'a /* 2538 */>() {
    let _: &'_ /* 56 */ () = &();
    let _: &'static /* 55 */ str /* 2104#4 */ = "";
}

We did not get the "hygiene comments" on the 'a, so we cannot tell that rustc thinks these are different lifetimes.

Key difference: Expected /* 2538#0 */ and /* 2538#1 */ (with distinct suffixes), but got /* 2538 */ for both (no suffix to distinguish them).

Meta

rustc --version --verbose:

rustc 1.95.0-nightly (873d4682c 2026-01-25)
binary: rustc
commit-hash: 873d4682c7d285540b8f28bfe637006cef8918a6
commit-date: 2026-01-25
host: x86_64-unknown-linux-gnu
release: 1.95.0-nightly
LLVM version: 21.1.8