error[E0506]: cannot assign to `greeting` because it is borrowed
  --> $DIR/issue-58776-borrowck-scans-children.rs:5:5
   |
LL |     let res = (|| (|| &greeting)())();
   |                --      -------- borrow occurs due to use in closure
   |                |
   |                borrow of `greeting` occurs here
LL |
LL |     greeting = "DEALLOCATED".to_string();
   |     ^^^^^^^^ assignment to borrowed `greeting` occurs here
...
LL |     println!("thread result: {:?}", res);
   |                                     --- borrow later used here

error[E0505]: cannot move out of `greeting` because it is borrowed
  --> $DIR/issue-58776-borrowck-scans-children.rs:7:10
   |
LL |     let res = (|| (|| &greeting)())();
   |                --      -------- borrow occurs due to use in closure
   |                |
   |                borrow of `greeting` occurs here
...
LL |     drop(greeting);
   |          ^^^^^^^^ move out of `greeting` occurs here
...
LL |     println!("thread result: {:?}", res);
   |                                     --- borrow later used here

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0505, E0506.
For more information about an error, try `rustc --explain E0505`.