collapsible_match might produce an incorrect suggestion for nested fields, when ref / mut / box modifiers are used #13287
Description
Description
enum Token {
Name,
Other,
}
struct Error {
location: u32,
token: Option<Token>,
}
fn add_anon_function_hint(err: Option<Error>) {
if let Some(Error { ref token, .. }) = err { // notice the `ref` part
if let Some(Token::Name) = token {
println!("token used as a ref");
}
}
}On main produces:
warning: this `if let` can be collapsed into the outer `if let`
--> compiler-core/src/regression.rs:13:9
|
13 | / if let Some(Token::Name) = token {
14 | | println!("Name error");
15 | | }
| |_________^
|
help: the outer pattern can be modified to include the inner pattern
--> compiler-core/src/regression.rs:12:25
|
12 | if let Some(Error { ref token, .. }) = err {
| ^^^^^^^^^ replace this binding
13 | if let Some(Token::Name) = token {
| ^^^^^^^^^^^^^^^^^ with this pattern, prefixed by `ref token:`
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_match
note: the lint level is defined here
--> compiler-core/src/lib.rs:2:5
|
2 | clippy::all,
| ^^^^^^^^^^^
= note: `#[warn(clippy::collapsible_match)]` implied by `#[warn(clippy::all)]`
Notice that "by ref token:" part. I think that it might be wrong.
Looks like if let Some(Error { ref token: Some(Token::Name), .. }) is not allowed by the grammar: https://github.com/intellij-rust/intellij-rust/blob/c6657c02bb62075bf7b7ceb84d000f93dda34dc1/src/main/grammars/RustParser.bnf#L642-L645
When this suggestion is applied I get:
error: expected `,`
--> compiler-core/src/regression.rs:12:34
|
12 | if let Some(Error { mut token: Some(Token::Name), .. }) = err {
| ----- ^
| |
| while parsing the fields for this pattern
error[E0425]: cannot find value `token` in this scope
--> compiler-core/src/regression.rs:13:36
|
13 | if let Some(Token::Name) = token {
| ^^^^^ not found in this scope
For more information about this error, try `rustc --explain E0425`.
The same is in question for box and mut.
Version
rustc 1.82.0-nightly (8b3870784 2024-08-07)
binary: rustc
commit-hash: 8b3870784f69d8ed2ae4246d1b56f150e3131499
commit-date: 2024-08-07
host: aarch64-apple-darwin
release: 1.82.0-nightly
LLVM version: 19.1.0
Additional Labels
No response