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A value was moved out while it was still borrowed.
Erroneous code example:
```compile_fail,E0505
struct Value {}
fn borrow(val: &Value) {}
fn eat(val: Value) {}
fn main() {
let x = Value{};
let _ref_to_val: &Value = &x;
eat(x);
borrow(_ref_to_val);
}
```
Here, the function `eat` takes ownership of `x`. However,
`x` cannot be moved because the borrow to `_ref_to_val`
needs to last till the function `borrow`.
To fix that you can do a few different things:
* Try to avoid moving the variable.
* Release borrow before move.
* Implement the `Copy` trait on the type.
Examples:
```
struct Value {}
fn borrow(val: &Value) {}
fn eat(val: &Value) {}
fn main() {
let x = Value{};
let ref_to_val: &Value = &x;
eat(&x); // pass by reference, if it's possible
borrow(ref_to_val);
}
```
Or:
```
struct Value {}
fn borrow(val: &Value) {}
fn eat(val: Value) {}
fn main() {
let x = Value{};
let ref_to_val: &Value = &x;
borrow(ref_to_val);
// ref_to_val is no longer used.
eat(x);
}
```
Or:
```
#[derive(Clone, Copy)] // implement Copy trait
struct Value {}
fn borrow(val: &Value) {}
fn eat(val: Value) {}
fn main() {
let x = Value{};
let ref_to_val: &Value = &x;
eat(x); // it will be copied here.
borrow(ref_to_val);
}
```
For more information on Rust's ownership system, take a look at the
[References & Borrowing][references-and-borrowing] section of the Book.
[references-and-borrowing]: https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html
|
