Bug when applying a fix for clippy::if-then-some-else-none #15395
Description
Summary
I have a block of code implementing next() for an iterator. Clippy reports a single warning in that file. Here's the unmodified source:
impl<'a, 'c> Iterator for Arguments<'a, 'c> {
type Item = Result<BlockArgument<'c, 'a>, Error>;
fn next(&mut self) -> Option<Self::Item> {
if self.idx < self.block.argument_count() {
let res = self.block.argument(self.idx);
self.idx += 1;
Some(res)
} else {
None
}
}
}This results in the following lint:
warning: this could be simplified with `bool::then`
--> src/codegen/melior_ext.rs:27:9
|
27 | / if self.idx < self.block.argument_count() {
28 | | let res = self.block.argument(self.idx);
29 | | self.idx += 1;
30 | | Some(res)
31 | | } else {
32 | | None
33 | | }
| |_________^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#if_then_some_else_none
= note: requested on the command line with `-W clippy::if-then-some-else-none`
help: try
|
27 ~ (self.idx < self.block.argument_count()).then(|| { let res = self.block.argument(self.idx);
28 + self.idx += 1;
29 + Some(; res })
|
And causes the fix to create broken code:
The following errors were reported:
error: mismatched closing delimiter: `}`
--> src/codegen/melior_ext.rs:29:17
|
29 | Some(; res })
| ^ ^ mismatched closing delimiter
| |
| unclosed delimiter
error: aborting due to 1 previous error
I created an MRE below.
Reproducer
I tried this code:
#![warn(clippy::if_then_some_else_none)]
fn main() -> Result<(), Box<dyn std::error::Error>> {
Ok(())
}
pub struct I {
arr: Vec<u64>,
idx: usize,
}
impl Iterator for I {
type Item = u64;
fn next(&mut self) -> Option<Self::Item> {
if self.idx < self.arr.len() {
let res = self.arr[self.idx];
self.idx += 1;
Some(res)
} else {
None
}
}
}Full output:
warning: failed to automatically apply fixes suggested by rustc to crate `rust_playground`
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-clippy/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: mismatched closing delimiter: `}`
--> src/main.rs:18:17
|
18 | Some(; res })
| ^ ^ mismatched closing delimiter
| |
| unclosed delimiter
error: aborting due to 1 previous error
Original diagnostics will follow.
warning: this could be simplified with `bool::then`
--> src/main.rs:16:9
|
16 | / if self.idx < self.arr.len() {
17 | | let res = self.arr[self.idx];
18 | | self.idx += 1;
19 | | Some(res)
20 | | } else {
21 | | None
22 | | }
| |_________^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#if_then_some_else_none
note: the lint level is defined here
--> src/main.rs:1:9
|
1 | #![warn(clippy::if_then_some_else_none)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: try
|
16 ~ (self.idx < self.arr.len()).then(|| { let res = self.arr[self.idx];
17 + self.idx += 1;
18 + Some(; res })
|
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-error