Open
Description
Summary
clippy::only_used_in_recursion can trip on self in methods. While this is technically correct, it is inconsistent with rustc's unused_variables lint.
Lint Name
clippy::only_used_in_recursion
Reproducer
I tried this code (playground):
pub enum Expression {
Path(usize),
Loop(Option<Box<Expression>>),
FnCall(Box<Expression>, Vec<Box<Expression>>),
}
impl Expression {
pub fn is_intrinsic(&self) -> bool {
todo!()
}
}
pub struct LowerState;
impl LowerState {
fn find_id(&self, expr: &Expression) -> Option<usize> {
match expr {
Expression::Path(id) => Some(*id),
Expression::FnCall(_, _) => None,
Expression::Loop(body) => body.as_ref().and_then(|expr| self.find_id(expr)),
}
}
pub fn lower_expression(&self, expr: Expression) {
match &expr {
Expression::Loop(_) => todo!(),
Expression::Path(_) => todo!(),
Expression::FnCall(f, _args) => {
if expr.is_intrinsic() {
let _id = self.find_id(f);
todo!()
}
todo!()
}
}
}
}I saw this happen:
warning: parameter is only used in recursion
--> src/lib.rs:16:17
|
16 | fn find_id(&self, expr: &Expression) -> Option<usize> {
| ^^^^
|
note: parameter used here
--> src/lib.rs:20:69
|
20 | Expression::Loop(body) => body.as_ref().and_then(|expr| self.find_id(expr)),
| ^^^^
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#only_used_in_recursion
= note: `#[warn(clippy::only_used_in_recursion)]` on by default
I expected to see this happen: No warnings
Note that if the body of LowerState::find_id is replaced with todo!(), self is not marked as unused (playground):
// ...
impl LowerState {
fn find_id(&self, expr: &Expression) -> Option<usize> {
todo!()
}
// ...
}warning: unused variable: `expr`
--> src/lib.rs:16:23
|
16 | fn find_id(&self, expr: &Expression) -> Option<usize> {
| ^^^^ help: if this is intentional, prefix it with an underscore: `_expr`
|
= note: `#[warn(unused_variables)]` on by default
Version
rustc 1.69.0-nightly (0416b1a6f 2023-02-14)
binary: rustc
commit-hash: 0416b1a6f6d5c42696494e1a3a33580fd3f669d8
commit-date: 2023-02-14
host: x86_64-unknown-linux-gnu
release: 1.69.0-nightly
LLVM version: 15.0.7
Additional Labels
No response