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;
   |
```

Fix #48677.

0 files changed, 0 insertions, 0 deletions