Example:
It seems to me this ought to
compile, or at least it's not clear to me why it doesn't. The following code yields:
errorE0502: cannot borrow `*
cache` as mutable because it is also borrowed as immutable
-->
src/lib.rs:12:5
|
6 | fn
compute<'cache>(input: i32, cache: &'cache
mut Cache) -> Cow<'cache, i32> {
| ------ lifetime `'cache` defined here
7 | if let Some(
cached) = cache.get(&input) {
| ----- immutable borrow occurs here
8 | return Cow::Borrowed(cached);
| --------------------- returning this value requires that `*cache` is borrowed for `'cache`
...
12 | cache.insert(input, result);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here
error: aborting due to previous error
For more information about this error, try `rustc --explain E0502`.