Fixes#14969.
The issue was that this line:
```rust
let from_assign_to_loop = TextRange::new(binding_stmt.end(), for_stmt.start());
```
was not safe if the binding was after the target. The only way (at least
that I can think of) this can happen is if they are in different scopes,
so it now checks for that before checking if there are usages between
the two.
4a7536dc94