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6c22e0419f
suggest `slice::swap` for `mem::swap(&mut x[0], &mut x[1])` borrowck error
Recently saw someone ask why this code (example slightly modified):
```rs
fn main() {
let mut foo = [1, 2];
std::mem::swap(&mut foo[0], &mut foo[1]);
}
```
triggers this error and how to fix it:
```
error[E0499]: cannot borrow `foo[_]` as mutable more than once at a time
--> src/main.rs:4:33
|
4 | std::mem::swap(&mut foo[0], &mut foo[1]);
| -------------- ----------- ^^^^^^^^^^^ second mutable borrow occurs here
| | |
| | first mutable borrow occurs here
| first borrow later used by call
|
= help: consider using `.split_at_mut(position)` or similar method to obtain two mutable non-overlapping sub-slices
```
The current help message is nice and goes in the right direction, but I think we can do better for this specific instance and suggest `slice::swap`, which makes this compile
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| .. | ||
| constraints | ||
| diagnostics | ||
| region_infer | ||
| type_check | ||
| util | ||
| borrow_set.rs | ||
| borrowck_errors.rs | ||
| constraint_generation.rs | ||
| consumers.rs | ||
| dataflow.rs | ||
| def_use.rs | ||
| facts.rs | ||
| invalidation.rs | ||
| lib.rs | ||
| location.rs | ||
| member_constraints.rs | ||
| nll.rs | ||
| path_utils.rs | ||
| place_ext.rs | ||
| places_conflict.rs | ||
| prefixes.rs | ||
| renumber.rs | ||
| session_diagnostics.rs | ||
| universal_regions.rs | ||
| used_muts.rs | ||