mirror of
https://github.com/rust-lang/rust
synced 2024-10-01 06:14:33 +00:00
cc80106cb5
When encountering multiple mutable borrows, suggest cloning and adding
derive annotations as needed.
```
error[E0596]: cannot borrow `sm.x` as mutable, as it is behind a `&` reference
--> $DIR/accidentally-cloning-ref-borrow-error.rs:32:9
|
LL | foo(&mut sm.x);
| ^^^^^^^^^ `sm` is a `&` reference, so the data it refers to cannot be borrowed as mutable
|
help: `Str` doesn't implement `Clone`, so this call clones the reference `&Str`
--> $DIR/accidentally-cloning-ref-borrow-error.rs:31:21
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LL | let mut sm = sr.clone();
| ^^^^^^^
help: consider annotating `Str` with `#[derive(Clone)]`
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LL + #[derive(Clone)]
LL | struct Str {
|
help: consider specifying this binding's type
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LL | let mut sm: &mut Str = sr.clone();
| ++++++++++
```
```
error[E0596]: cannot borrow `*inner` as mutable, as it is behind a `&` reference
--> $DIR/issue-91206.rs:14:5
|
LL | inner.clear();
| ^^^^^ `inner` is a `&` reference, so the data it refers to cannot be borrowed as mutable
|
help: you can `clone` the `Vec<usize>` value and consume it, but this might not be your desired behavior
--> $DIR/issue-91206.rs:11:17
|
LL | let inner = client.get_inner_ref();
| ^^^^^^^^^^^^^^^^^^^^^^
help: consider specifying this binding's type
|
LL | let inner: &mut Vec<usize> = client.get_inner_ref();
| +++++++++++++++++
```
39 lines
714 B
Rust
39 lines
714 B
Rust
#[derive(Debug)]
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struct X<T>(T);
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impl<T: Clone> Clone for X<T> {
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fn clone(&self) -> X<T> {
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X(self.0.clone())
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}
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}
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#[derive(Debug)]
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struct Y;
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#[derive(Debug)]
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struct Str {
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x: Option<i32>,
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}
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fn foo(s: &mut Option<i32>) {
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if s.is_none() {
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*s = Some(0);
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}
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println!("{:?}", s);
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}
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fn bar<T: std::fmt::Debug>(s: &mut X<T>) {
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println!("{:?}", s);
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}
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fn main() {
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let s = Str { x: None };
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let sr = &s;
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let mut sm = sr.clone();
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foo(&mut sm.x); //~ ERROR cannot borrow `sm.x` as mutable, as it is behind a `&` reference
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let x = X(Y);
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let xr = &x;
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let mut xm = xr.clone();
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bar(&mut xm); //~ ERROR cannot borrow data in a `&` reference as mutable
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}
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