unnecessary_operation destroyes code inside macros

[matthiaskrgr]

Summary

.

Lint Name

unnecessary_operation

Reproducer

I tried this code:

#![allow(unused_must_use)]
#![feature(rustc_attrs)]

use std::thread;

trait Int {
    fn zero() -> Self;
    fn one() -> Self;
}
macro_rules! doit {
    ($($t:ident)*) => ($(impl Int for $t {
        fn zero() -> Self { 0 }
        fn one() -> Self { 1 }
    })*)
}
doit! { i8 isize }

macro_rules! check {
    ($($e:expr),*) => {
        $(assert!(thread::spawn({
            move|| { $e; } // RIP
        }).join().is_err());)*
    }
}

fn main() {
    check![
        isize::MIN / -isize::one(),
        i8::MIN / -i8::one()
    ];
}

I saw this happen:
cargo clippy ---fix

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

  * src/main.rs

This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag

The following errors were reported:
error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth
  --> src/main.rs:20:10
   |
20 |           $(assert!(thread::spawn({
   |  __________^
21 | |             move|| { i8::MIN;-i8::one(); } // RIP
22 | |         }).join().is_err());)*
   | |_____________________________^

warning: unused import: `std::thread`
 --> src/main.rs:4:5
  |
4 | use std::thread;
  |     ^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

error: aborting due to previous error; 1 warning emitted

Original diagnostics will follow.

warning: unnecessary operation
  --> src/main.rs:21:22
   |
21 |               move|| { $e; } // RIP
   |                        ^^^ help: statement can be reduced to: `isize::MIN;-isize::one();`
...
27 | /     check![
28 | |         isize::MIN / -isize::one(),
29 | |         i8::MIN / -i8::one()
30 | |     ];
   | |_____- in this macro invocation
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_operation
   = note: `#[warn(clippy::unnecessary_operation)]` on by default
   = note: this warning originates in the macro `check` (in Nightly builds, run with -Z macro-backtrace for more info)

warning: unnecessary operation
  --> src/main.rs:21:22
   |
21 |               move|| { $e; } // RIP
   |                        ^^^ help: statement can be reduced to: `i8::MIN;-i8::one();`
...
27 | /     check![
28 | |         isize::MIN / -isize::one(),
29 | |         i8::MIN / -i8::one()
30 | |     ];
   | |_____- in this macro invocation
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_operation
   = note: this warning originates in the macro `check` (in Nightly builds, run with -Z macro-backtrace for more info)

Version

rustc 1.67.0-nightly (b3bc6bf31 2022-11-24)
binary: rustc
commit-hash: b3bc6bf31265ac10946a0832092dbcedf9b26805
commit-date: 2022-11-24
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

Additional Labels

No response