Closed
Description
Summary
The useless_asref lint (in rust 1.77) suggests a fix that does not compile.
Perhaps related to #12148?
Lint Name
useless_asref
Reproducer
I tried this code:
use std::ops::Deref;
use std::sync::Arc;
pub struct Wrap<T> {
inner: T,
}
impl<T> Deref for Wrap<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.inner
}
}
pub struct Thing {
current: Option<Wrap<Arc<u32>>>,
}
impl Thing {
pub fn fetch(&self) -> Option<Arc<u32>> {
self.current.as_ref().map(|p| Arc::clone(p))
}
}I saw this happen:
warning: this call to `as_ref.map(...)` does nothing
--> src/lib.rs:22:9
|
22 | self.current.as_ref().map(|p| Arc::clone(p))
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `self.current.clone()`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_asref
= note: `#[warn(clippy::useless_asref)]` on by default
And if I apply the suggestion:
error[E0599]: the method `clone` exists for enum `Option<Wrap<Arc<u32>>>`, but its trait bounds were not satisfied
--> src/lib.rs:22:22
|
4 | pub struct Wrap<T> {
| ------------------ doesn't satisfy `Wrap<Arc<u32>>: Clone`
...
22 | self.current.clone()
| ^^^^^ method cannot be called on `Option<Wrap<Arc<u32>>>` due to unsatisfied trait bounds
|
|
570 | pub enum Option<T> {
| ------------------ doesn't satisfy `Option<Wrap<Arc<u32>>>: Clone`
|
= note: the following trait bounds were not satisfied:
`Wrap<Arc<u32>>: Clone`
which is required by `Option<Wrap<Arc<u32>>>: Clone`
I expected to see this happen:
Either no lint should fire, or the suggested fix should compile.
Version
rustc 1.77.0 (aedd173a2 2024-03-17)
binary: rustc
commit-hash: aedd173a2c086e558c2b66d3743b344f977621a7
commit-date: 2024-03-17
host: x86_64-unknown-linux-gnu
release: 1.77.0
LLVM version: 17.0.6