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14473adf42
When encountering a move error on a value within a loop of any kind,
identify if the moved value belongs to a call expression that should not
be cloned and avoid the semantically incorrect suggestion. Also try to
suggest moving the call expression outside of the loop instead.
```
error[E0382]: use of moved value: `vec`
--> $DIR/recreating-value-in-loop-condition.rs:6:33
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LL | let vec = vec!["one", "two", "three"];
| --- move occurs because `vec` has type `Vec<&str>`, which does not implement the `Copy` trait
LL | while let Some(item) = iter(vec).next() {
| ----------------------------^^^--------
| | |
| | value moved here, in previous iteration of loop
| inside of this loop
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note: consider changing this parameter type in function `iter` to borrow instead if owning the value isn't necessary
--> $DIR/recreating-value-in-loop-condition.rs:1:17
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LL | fn iter<T>(vec: Vec<T>) -> impl Iterator<Item = T> {
| ---- ^^^^^^ this parameter takes ownership of the value
| |
| in this function
help: consider moving the expression out of the loop so it is only moved once
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LL ~ let mut value = iter(vec);
LL ~ while let Some(item) = value.next() {
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```
We use the presence of a `break` in the loop that would be affected by
the moved value as a heuristic for "shouldn't be cloned".
Fix #121466.
35 lines
785 B
Rust
35 lines
785 B
Rust
#![allow(dead_code)]
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struct Events<R>(R);
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struct Other;
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pub trait Trait<T> {
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fn handle(value: T) -> Self;
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}
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// Blanket impl. (If you comment this out, compiler figures out that it
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// is passing an `&mut` to a method that must be expecting an `&mut`,
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// and injects an auto-reborrow.)
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impl<T, U> Trait<U> for T where T: From<U> {
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fn handle(_: U) -> Self { unimplemented!() }
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}
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impl<'a, R> Trait<&'a mut Events<R>> for Other {
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fn handle(_: &'a mut Events<R>) -> Self { unimplemented!() }
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}
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fn this_compiles<'a, R>(value: &'a mut Events<R>) {
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for _ in 0..3 {
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Other::handle(&mut *value);
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}
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}
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fn this_does_not<'a, R>(value: &'a mut Events<R>) {
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for _ in 0..3 {
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Other::handle(value); //~ ERROR use of moved value: `value`
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}
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}
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fn main() {}
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