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Rollup merge of #122254 - estebank:issue-48677, r=oli-obk
Detect calls to .clone() on T: !Clone types on borrowck errors
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;
|
```
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,32 @@ | ||
| //@ run-rustfix | ||
| fn foo<T: Default + Clone>(list: &mut Vec<T>) { | ||
| let mut cloned_items = Vec::new(); | ||
| for v in list.iter() { | ||
| cloned_items.push(v.clone()) | ||
| } | ||
| list.push(T::default()); | ||
| //~^ ERROR cannot borrow `*list` as mutable because it is also borrowed as immutable | ||
| drop(cloned_items); | ||
| } | ||
| fn bar<T: std::fmt::Display + Clone>(x: T) { | ||
| let a = &x; | ||
| let b = a.clone(); | ||
| drop(x); | ||
| //~^ ERROR cannot move out of `x` because it is borrowed | ||
| println!("{b}"); | ||
| } | ||
| #[derive(Debug)] | ||
| #[derive(Clone)] | ||
| struct A; | ||
| fn qux(x: A) { | ||
| let a = &x; | ||
| let b = a.clone(); | ||
| drop(x); | ||
| //~^ ERROR cannot move out of `x` because it is borrowed | ||
| println!("{b:?}"); | ||
| } | ||
| fn main() { | ||
| foo(&mut vec![1, 2, 3]); | ||
| bar(""); | ||
| qux(A); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,31 @@ | ||
| //@ run-rustfix | ||
| fn foo<T: Default>(list: &mut Vec<T>) { | ||
| let mut cloned_items = Vec::new(); | ||
| for v in list.iter() { | ||
| cloned_items.push(v.clone()) | ||
| } | ||
| list.push(T::default()); | ||
| //~^ ERROR cannot borrow `*list` as mutable because it is also borrowed as immutable | ||
| drop(cloned_items); | ||
| } | ||
| fn bar<T: std::fmt::Display>(x: T) { | ||
| let a = &x; | ||
| let b = a.clone(); | ||
| drop(x); | ||
| //~^ ERROR cannot move out of `x` because it is borrowed | ||
| println!("{b}"); | ||
| } | ||
| #[derive(Debug)] | ||
| struct A; | ||
| fn qux(x: A) { | ||
| let a = &x; | ||
| let b = a.clone(); | ||
| drop(x); | ||
| //~^ ERROR cannot move out of `x` because it is borrowed | ||
| println!("{b:?}"); | ||
| } | ||
| fn main() { | ||
| foo(&mut vec![1, 2, 3]); | ||
| bar(""); | ||
| qux(A); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,64 @@ | ||
| 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:14:10 | ||
| | | ||
| LL | fn bar<T: std::fmt::Display>(x: T) { | ||
| | - 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 `&T` because `T` doesn't implement `Clone` | ||
| LL | drop(x); | ||
| | ^ move out of `x` occurs here | ||
| LL | | ||
| LL | println!("{b}"); | ||
| | --- borrow later used here | ||
| | | ||
| help: consider further restricting this bound | ||
| | | ||
| LL | fn bar<T: std::fmt::Display + Clone>(x: 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; | ||
| | | ||
|
|
||
| error: aborting due to 3 previous errors | ||
|
|
||
| Some errors have detailed explanations: E0502, E0505. | ||
| For more information about an error, try `rustc --explain E0502`. |
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