manual_assert mangles code and introduces syntax errors

[matthiaskrgr]

Summary

.

Lint Name

manual_assert

Reproducer

I tried this code:

#![deny(clippy::fallible_impl_from)]
#![allow(clippy::uninlined_format_args)]

// docs example
struct Foo(i32);
impl From<String> for Foo {
    fn from(s: String) -> Self {
        Foo(s.parse().unwrap())
    }
}

struct Invalid;

impl From<usize> for Invalid {
    fn from(i: usize) -> Invalid {
        if i != 42 {
            panic!();
        }
        Invalid
    }
}

impl From<Option<String>> for Invalid {
    fn from(s: Option<String>) -> Invalid {
        let s = s.unwrap();
        if !s.is_empty() {
            panic!("42");
        } else if s.parse::<u32>().unwrap() != 42 {
            panic!("{:?}", s);
        }
        Invalid
    }
}

fn main() {}

I saw this happen:
Looks like the suggestion eats the curly braces from the else block :/

cargo clippy --fix -- -Wclippy::manual_assert

   Checking a v0.1.0 (/tmp/a)
warning: failed to automatically apply fixes suggested by rustc to crate `a`

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: expected `{`, found `assert`
  --> src/main.rs:28:16
   |
28 |         } else assert!(!(s.parse::<u32>().unwrap() != 42), "{:?}", s);
   |                ^^^^^^ expected `{`
   |
help: try placing this code inside a block
   |
28 |         } else { assert!(!(s.parse::<u32>().unwrap() != 42), "{:?}", s) };
   |                +                                                        +

error: aborting due to previous error

Original diagnostics will follow.

warning: consider implementing `TryFrom` instead
  --> src/main.rs:6:1
   |
6  | / impl From<String> for Foo {
7  | |     fn from(s: String) -> Self {
8  | |         Foo(s.parse().unwrap())
9  | |     }
10 | | }
   | |_^
   |
   = help: `From` is intended for infallible conversions only. Use `TryFrom` if there's a possibility for the conversion to fail
note: potential failure(s)
  --> src/main.rs:8:13
   |
8  |         Foo(s.parse().unwrap())
   |             ^^^^^^^^^^^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#fallible_impl_from
note: the lint level is defined here
  --> src/main.rs:1:9
   |
1  | #![deny(clippy::fallible_impl_from)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: consider implementing `TryFrom` instead
  --> src/main.rs:14:1
   |
14 | / impl From<usize> for Invalid {
15 | |     fn from(i: usize) -> Invalid {
16 | |         if i != 42 {
17 | |             panic!();
...  |
20 | |     }
21 | | }
   | |_^
   |
   = help: `From` is intended for infallible conversions only. Use `TryFrom` if there's a possibility for the conversion to fail
note: potential failure(s)
  --> src/main.rs:17:13
   |
17 |             panic!();
   |             ^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#fallible_impl_from
   = note: this warning originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)

warning: consider implementing `TryFrom` instead
  --> src/main.rs:23:1
   |
23 | / impl From<Option<String>> for Invalid {
24 | |     fn from(s: Option<String>) -> Invalid {
25 | |         let s = s.unwrap();
26 | |         if !s.is_empty() {
...  |
32 | |     }
33 | | }
   | |_^
   |
   = help: `From` is intended for infallible conversions only. Use `TryFrom` if there's a possibility for the conversion to fail
note: potential failure(s)
  --> src/main.rs:25:17
   |
25 |         let s = s.unwrap();
   |                 ^^^^^^^^^^
26 |         if !s.is_empty() {
27 |             panic!("42");
   |             ^^^^^^^^^^^^
28 |         } else if s.parse::<u32>().unwrap() != 42 {
   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^
29 |             panic!("{:?}", s);
   |             ^^^^^^^^^^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#fallible_impl_from
   = note: this warning originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)

warning: only a `panic!` in `if`-then statement
  --> src/main.rs:28:16
   |
28 |           } else if s.parse::<u32>().unwrap() != 42 {
   |  ________________^
29 | |             panic!("{:?}", s);
30 | |         }
   | |_________^ help: try instead: `assert!(!(s.parse::<u32>().unwrap() != 42), "{:?}", s);`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_assert
   = note: requested on the command line with `-W clippy::manual-assert`

Version

rustc 1.67.0-nightly (b833ad56f 2022-11-18)
binary: rustc
commit-hash: b833ad56f46a0bbe0e8729512812a161e7dae28a
commit-date: 2022-11-18
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

Additional Labels

No response