I have the following code which I would expect to work.
let mut some_str: &'static str = "Hello world";
let _borrow: &'static mut &'static str = &mut some_str;
However when I compile this I get:
--> src/lib.rs:26:50
|
25 | let mut some_str: &'static str = "Hello world";
| ------------ binding `some_str` declared here
26 | let _borrow: &'static mut &'static str = &mut some_str;
| ------------------------- ^^^^^^^^^^^^^ borrowed value does not live long enough
| |
| type annotation requires that `some_str` is borrowed for `'static`
27 | }
| - `some_str` dropped here while still borrowed
This tells me that some_str is being dopped before borrow however, both references are static so I would expect both references to have the same lifetime, which is not the case. Why does this happens? Is a static life time shorter than another or am I misunderstanding the error code?
>Solution :
The lifetime annotation always describes the lifetime of the pointee, not the pointer. The data some_str is pointing to has static lifetime. The pointer itself is a local variable, and as all local variables it is dropped at the end of the function.