match_single_binding suggests code with invalid syntax

[antonilol]

Summary

a suggestion from the match_single_binding lint includes invalid syntax

posted here but later thought "people with notifications for new issues won't notice that"
could be fixed by #15060

Reproducer

I tried this code:

fn what(a: usize, b: usize, c: usize) -> bool {
    a < b
        && match b {
            b => b < c,
        }
}

I expected to see this happen:
match_single_binding suggests something like this:

fn what(a: usize, b: usize, c: usize) -> bool {
    a < b
        && b < c
}

Instead, this happened:
match_single_binding suggests this:

fn what(a: usize, b: usize, c: usize) -> bool {
    a < b
        && let b = b;
        b < c
}

Version

rustc 1.88.0 (6b00bc388 2025-06-23)
binary: rustc
commit-hash: 6b00bc3880198600130e1cf62b8f8a93494488cc
commit-date: 2025-06-23
host: x86_64-unknown-linux-gnu
release: 1.88.0
LLVM version: 20.1.5

Additional Labels

@rustbot label +I-suggestion-causes-bug

[blyxyas]

Just tested #15060, it won't fix this issue.