let_and_return false positive #1669
Description
#![feature(conservative_impl_trait)]
fn pairs<'a, T>(items: &'a [T]) -> impl Iterator<Item=(&'a T, &'a T)> + 'a {
items.iter().map(|i| (i, i))
}
fn foo() -> usize {
let data = vec![0, 1, 2, 3];
let result = pairs(&data).count();
result
}
fn main() {
foo();
}
warning: returning the result of a let binding from a block. Consider returning the expression directly.
--> src\main.rs:8:5
|
8 | result
| ^^^^^^
|
= note: #[warn(let_and_return)] on by default
note: this expression can be directly returned
--> src\main.rs:7:18
|
7 | let result = pairs(&data).count();
| ^^^^^^^^^^^^^^^^^^^^
= help: for further information visit https://github.com/Manishearth/rust-clippy/wiki#let_and_return
If I modify the code as suggested, it stops compiling:
#![feature(conservative_impl_trait)]
fn pairs<'a, T>(items: &'a [T]) -> impl Iterator<Item=(&'a T, &'a T)> + 'a {
items.iter().map(|i| (i, i))
}
fn foo() -> usize {
let data = vec![0, 1, 2, 3];
pairs(&data).count()
}
fn main() {
foo();
}
Rustc gives:
error: `data` does not live long enough
--> ...\main.rs:8:1
|
7 | pairs(&data).count()
| ---- borrow occurs here
8 | }
| ^ `data` dropped here while still borrowed
|
= note: values in a scope are dropped in the opposite order they are created