mirror of
https://github.com/rust-lang/rust
synced 2024-10-14 12:33:57 +00:00
2d3435b4df
When encountering a lifetime error on a type that *holds* a type that
doesn't implement `Clone`, explore the item's body for potential calls
to `.clone()` that are only cloning the reference `&T` instead of `T`
because `T: !Clone`. If we find this, suggest `T: Clone`.
```
error[E0502]: cannot borrow `*list` as mutable because it is also borrowed as immutable
--> $DIR/clone-on-ref.rs:7:5
|
LL | for v in list.iter() {
| ---- immutable borrow occurs here
LL | cloned_items.push(v.clone())
| ------- this call doesn't do anything, the result is still `&T` because `T` doesn't implement `Clone`
LL | }
LL | list.push(T::default());
| ^^^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here
LL |
LL | drop(cloned_items);
| ------------ immutable borrow later used here
|
help: consider further restricting this bound
|
LL | fn foo<T: Default + Clone>(list: &mut Vec<T>) {
| +++++++
```
```
error[E0505]: cannot move out of `x` because it is borrowed
--> $DIR/clone-on-ref.rs:23:10
|
LL | fn qux(x: A) {
| - binding `x` declared here
LL | let a = &x;
| -- borrow of `x` occurs here
LL | let b = a.clone();
| ------- this call doesn't do anything, the result is still `&A` because `A` doesn't implement `Clone`
LL | drop(x);
| ^ move out of `x` occurs here
LL |
LL | println!("{b:?}");
| ----- borrow later used here
|
help: consider annotating `A` with `#[derive(Clone)]`
|
LL + #[derive(Clone)]
LL | struct A;
|
```
33 lines
763 B
Rust
33 lines
763 B
Rust
//@ run-rustfix
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fn foo<T: Default + Clone>(list: &mut Vec<T>) {
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let mut cloned_items = Vec::new();
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for v in list.iter() {
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cloned_items.push(v.clone())
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}
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list.push(T::default());
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//~^ ERROR cannot borrow `*list` as mutable because it is also borrowed as immutable
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drop(cloned_items);
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}
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fn bar<T: std::fmt::Display + Clone>(x: T) {
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let a = &x;
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let b = a.clone();
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drop(x);
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//~^ ERROR cannot move out of `x` because it is borrowed
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println!("{b}");
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}
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#[derive(Debug)]
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#[derive(Clone)]
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struct A;
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fn qux(x: A) {
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let a = &x;
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let b = a.clone();
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drop(x);
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//~^ ERROR cannot move out of `x` because it is borrowed
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println!("{b:?}");
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}
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fn main() {
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foo(&mut vec![1, 2, 3]);
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bar("");
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qux(A);
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}
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