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Irritating "unused" warning #108885
Description
Code
fn main() {
let mut vec = vec![[0].iter(), [1].iter()];
vec.remove(0);
}Current output
warning: unused `std::slice::Iter` that must be used
--> src\main.rs:52:5
|
52 | vec.remove(0);
| ^^^^^^^^^^^^^^
|
= note: iterators are lazy and do nothing unless consumedDesired output
No warning when nothing is done to an iterator or similar when they are returned from a function with side effects.
If a warning is shown, it should be like this:
warning: unused return value.
You can use `let _ = vec.remove(0)` to signify that dropping it without usage is the intended behavior.Rationale and extra context
rustc finds that remove returns an iterator.
Obviously I am not doing anything with it.
But the of the line is not to do something with the iterator, but to remove it from the list.
Other cases
No response
Anything else?
No response
Activity
workingjubilee commentedon Mar 8, 2023
You may silence the warning with
let _ = vec.remove(0);workingjubilee commentedon Mar 8, 2023
This diagnostic should recommend that.
FlorianDyck commentedon Mar 8, 2023
In this case I think the output could be improved to:
warning: unused return value.
You can use "let _ = ..." to signify that dropping it without usage is the intended behavior.
Ezrashaw commentedon Mar 11, 2023
@rustbot claim
Rollup merge of rust-lang#109158 - Ezrashaw:expand-sugg-for-unused-li…