const statement body expr formatting changed (unexpectedly?)

[jieyouxu]

Summary

I tried to format this code: stage0 bump https://github.com/rust-lang/rust/pull/162040/changes#diff-29bf34e005bfe0956e60f3713ab0290027a3c97ce8c2112f818fe4f90b41d82e

pub const POLY_CONST_1<const C: bool>: () = if C { func3() };

Expected behavior

I expected to see this happen: no formatting changes?

Maybe the new formatting is fine, but this should be deliberate and not accidental.

Actual behavior

Instead, this happened: formatting has changed

$ rustfmt +nightly ../reproducer/foo.rs --config-path=/dev/null --style-edition=2024 --edition=2024 --check
Diff in /home/joe/repos/reproducer/foo.rs:1:
-pub const POLY_CONST_1<const C: bool>: () = if C { func3() };
+pub const POLY_CONST_1<const C: bool>: () = if C {
+    func3()
+};

Meta

Version it worked on

It most recently worked on: beta rustfmt 1.10.0-beta (cbae9b4cae 2026-08-28)

Version with regression

Nightly.

rustfmt 1.10.0-nightly (5db7f4be8a 2026-09-01)

I bisected the rust-lang/rust side to the subtree sync rust-lang/rust#161964 (since we recently updated stage0 rustfmt to the commit of that subtree sync). Within that subtree sync, I did manual guessing and bisected to #6956 by reverting the change to see if the formatting difference goes away.

@rustbot modify labels: +regression-from-stable-to-nightly -regression-untriaged

[jieyouxu]

Backlink to discussion: #t-rustfmt > Formatting diff in stage0 bump for 1.100.0-nightly

[ytmimi]

@jieyouxu I think we can safely close this one. The diff in tests/codegen-llvm/private-const-fn-only-used-in-const-eval.rs is directly related to #6956, which implemented formatting for the nightly only #![feature(generic_const_items)]