Incorrect semi-colon placement in clippy::let_unit_value

[ogghostjelly]

Summary

I tried to run cargo clippy --fix and received the following error:

after fixes were automatically applied the compiler reported errors within these files:

  * src/reader/reader.rs

The following errors were reported:
error: expected one of `,`, `.`, `?`, `}`, or an operator, found `;`
   --> src/reader/reader.rs:141:52
    |
141 |                     Char::Char(ch) => self.next(ch);,
    |                                    --              ^ expected one of `,`, `.`, `?`, `}`, or an operator
    |                                    |
    |                                    while parsing the `match` arm starting here

This is the warning it was trying to fix before crashing:

warning: this let-binding has unit value
   --> src/reader/reader.rs:141:39
    |
141 |                     Char::Char(ch) => _ = self.next(ch),
    |                                       ^^^^^^^^^^^^^^^^^ help: omit the `let` binding: `self.next(ch);`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_unit_value
    = note: `#[warn(clippy::let_unit_value)]` on by default

It should not be inserting a semicolon in that location.

Reproducer

I tried this code:

fn do_nothing() -> () {
    ()
}

fn main() {
    match "Example String" {
        _ => _ = do_nothing(),
    }
}

I expected to see this happen:

The useless let binding to be removed, and the fix to be successful.

Instead, this happened:

Clippy inserted a semi-colon where there should not be one, leading to a syntax error.

Version

rustc 1.90.0 (1159e78c4 2025-09-14)
binary: rustc
commit-hash: 1159e78c4747b02ef996e55082b704c09b970588
commit-date: 2025-09-14
host: x86_64-unknown-linux-gnu
release: 1.90.0
LLVM version: 20.1.8

Additional Labels

@rustbot label +I-suggestion-causes-error

[ada4a]

@rustbot claim