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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; | ```
65 lines
2.2 KiB
Plaintext
65 lines
2.2 KiB
Plaintext
error[E0502]: cannot borrow `*list` as mutable because it is also borrowed as immutable
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--> $DIR/clone-on-ref.rs:7:5
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LL | for v in list.iter() {
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| ---- immutable borrow occurs here
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LL | cloned_items.push(v.clone())
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| ------- this call doesn't do anything, the result is still `&T` because `T` doesn't implement `Clone`
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LL | }
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LL | list.push(T::default());
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| ^^^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here
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LL |
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LL | drop(cloned_items);
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| ------------ immutable borrow later used here
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help: consider further restricting this bound
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LL | fn foo<T: Default + Clone>(list: &mut Vec<T>) {
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| +++++++
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error[E0505]: cannot move out of `x` because it is borrowed
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--> $DIR/clone-on-ref.rs:14:10
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LL | fn bar<T: std::fmt::Display>(x: T) {
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| - binding `x` declared here
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LL | let a = &x;
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| -- borrow of `x` occurs here
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LL | let b = a.clone();
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| ------- this call doesn't do anything, the result is still `&T` because `T` doesn't implement `Clone`
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LL | drop(x);
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| ^ move out of `x` occurs here
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LL |
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LL | println!("{b}");
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| --- borrow later used here
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help: consider further restricting this bound
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LL | fn bar<T: std::fmt::Display + Clone>(x: T) {
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| +++++++
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error[E0505]: cannot move out of `x` because it is borrowed
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--> $DIR/clone-on-ref.rs:23:10
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LL | fn qux(x: A) {
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| - binding `x` declared here
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LL | let a = &x;
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| -- borrow of `x` occurs here
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LL | let b = a.clone();
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| ------- this call doesn't do anything, the result is still `&A` because `A` doesn't implement `Clone`
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LL | drop(x);
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| ^ move out of `x` occurs here
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LL |
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LL | println!("{b:?}");
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| ----- borrow later used here
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help: consider annotating `A` with `#[derive(Clone)]`
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LL + #[derive(Clone)]
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LL | struct A;
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error: aborting due to 3 previous errors
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Some errors have detailed explanations: E0502, E0505.
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For more information about an error, try `rustc --explain E0502`.
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