`if_then_panic` causes "cannot apply unary operator `!` to type"

[stevenengler]

I tried this code:

fn main() {
    if "a" != "a" {
        panic!();
    }
}

I expected to see this happen: The --fix operation to be successful.

Instead, this happened:

$ cargo +nightly clippy --fix
    Checking clippy-bug v0.1.0 (clippy-bug)
warning: failed to automatically apply fixes suggested by rustc to crate `clippy_bug`

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[E0600]: cannot apply unary operator `!` to type `&'static str`
 --> src/main.rs:2:13
  |
2 |     assert!(!"a" != "a", ..);
  |             ^^^^ cannot apply unary operator `!`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0600`.
Original diagnostics will follow.

warning: only a `panic!` in `if`-then statement
 --> src/main.rs:2:5
  |
2 | /     if "a" != "a" {
3 | |         panic!();
4 | |     }
  | |_____^ help: try: `assert!(!"a" != "a", ..);`
  |
  = note: `#[warn(clippy::if_then_panic)]` on by default
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#if_then_panic

warning: equal expressions as operands to `!=`
 --> src/main.rs:2:8
  |
2 |     if "a" != "a" {
  |        ^^^^^^^^^^
  |
  = note: `#[warn(clippy::eq_op)]` on by default
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#eq_op

warning: `clippy-bug` (bin "clippy-bug") generated 2 warnings
warning: `clippy-bug` (bin "clippy-bug" test) generated 2 warnings (2 duplicates)
    Finished dev [unoptimized + debuginfo] target(s) in 0.09s

Meta

Rust version (rustc -Vv):

rustc 1.57.0-nightly (9dbb26efe 2021-10-03)
binary: rustc
commit-hash: 9dbb26efe8a886f7bba94c2b996c9535ce07f917
commit-date: 2021-10-03
host: x86_64-unknown-linux-gnu
release: 1.57.0-nightly
LLVM version: 13.0.0

[giraffate]

It was fixed at #7741, so I'm closing this.

FYI suggestion will be improved in #7716.