Compile error after applying clippy::map_entry #13934
Description
Summary
After applying a clippy::map_entry suggested fix, the generated code fails to compile. Clippy appears unable to see uses of the given map from within method calls on the same struct.
Lint Name
clippy::map_entry
Reproducer
I tried this code:
use std::collections::HashMap;
struct Member {}
pub struct Foo {
members: HashMap<u8, Member>,
}
impl Foo {
pub fn bar(&mut self, input: u8) -> Result<(), String> {
if self.members.contains_key(&input) {
Err("already exists".to_string())
} else {
self.other();
self.members.insert(input, Member {});
Ok(())
}
}
fn other(&self) {
for key in self.members.keys() {
println!("key: {}", key);
}
}
}I saw this happen:
Checking playground v0.0.1 (/playground)
warning: usage of `contains_key` followed by `insert` on a `HashMap`
--> src/lib.rs:11:9
|
11 | / if self.members.contains_key(&input) {
12 | | Err("already exists".to_string())
13 | | } else {
14 | | self.other();
15 | | self.members.insert(input, Member {});
16 | | Ok(())
17 | | }
| |_________^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#map_entry
= note: `#[warn(clippy::map_entry)]` on by default
help: try
|
11 ~ if let std::collections::hash_map::Entry::Vacant(e) = self.members.entry(input) {
12 + self.other();
13 + e.insert(Member {});
14 + Ok(())
15 + } else {
16 + Err("already exists".to_string())
17 + }
|
warning: `playground` (lib) generated 1 warning (run `cargo clippy --fix --lib -p playground` to apply 1 suggestion)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.46s
When applied to the original code, this suggestion fails to compile with this error:
Compiling playground v0.0.1 (/playground)
error[E0502]: cannot borrow `*self` as immutable because it is also borrowed as mutable
--> src/lib.rs:12:14
|
11 | if let std::collections::hash_map::Entry::Vacant(e) = self.members.entry(input) {
| ------------ mutable borrow occurs here
12 | self.other();
| ^^^^ immutable borrow occurs here
13 | e.insert(Member {});
| - mutable borrow later used here
For more information about this error, try `rustc --explain E0502`.
error: could not compile `playground` (lib) due to 1 previous error
I expected to see this happen:
I expect clippy to not make this suggestion at all.
Version
rustc 1.83.0 (90b35a623 2024-11-26)
binary: rustc
commit-hash: 90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf
commit-date: 2024-11-26
host: aarch64-apple-darwin
release: 1.83.0
LLVM version: 19.1.1
Additional Labels
@rustbot label +l-suggestion-causes-error