error[E0515]: cannot yield value referencing local variable `s`
  --> $DIR/issue-55850.rs:28:9
   |
LL |         yield &s[..]
   |         ^^^^^^^-^^^^
   |         |      |
   |         |      `s` is borrowed here
   |         yields a value referencing data owned by the current function

error[E0626]: borrow may still be in use when coroutine yields
  --> $DIR/issue-55850.rs:28:16
   |
LL |     GenIter(#[coroutine] move || {
   |                          ------- within this coroutine
LL |         let mut s = String::new();
LL |         yield &s[..]
   |         -------^---- possible yield occurs here
   |
help: add `static` to mark this coroutine as unmovable
   |
LL |     GenIter(#[coroutine] static move || {
   |                          ++++++

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0515, E0626.
For more information about an error, try `rustc --explain E0515`.