Variable appears to be borrowed by itself with NLL

[Aaron1011]

Compiling this code snippet:

#![feature(nll)]

struct Foo;

impl Foo {
    fn get_self(&mut self) -> Option<&mut Self> {
        Some(self)
    }

    fn new_self(&mut self) -> &mut Self {
        self
    }
    
    fn trigger_bug(&mut self) {
        let other = &mut (&mut *self);
        
        *other = match (*other).get_self() {
            Some(s) => s,
            None => (*other).new_self()
        };
        
        let c = other;
        
    }
}

fn main() {}

gives the following error:

error[E0505]: cannot move out of `other` because it is borrowed
  --> src/main.rs:22:17
   |
17 |         *other = match (*other).get_self() {
   |                        -------- borrow of `**other` occurs here
...
22 |         let c = other;
   |                 ^^^^^ move out of `other` occurs here

After the *other = ... assignment, it appears to be impossible to interact with other in any way, including moving and borrowing it. Effectively, it appears to be borrowed by itself.

[nikomatsakis]

I believe this is because we only "kill" loans for assignments directly to local variables right now.

[nikomatsakis]

Pushing to RC, this is a minor addition.

[nikomatsakis]

This is also a dup of #46589, really, so maybe I'll just move the example there and close it.

[nikomatsakis]

Closing as duplicate.