Auto merge of #10368 - c410-f3r:lock-1, r=xFrednet

[significant_drop_tightening] Evaluate the return expression of a block

For whatever reason, the return expression of a block is not contained inside the slice of statements and because of that the lint wasn't evaluating things that could potentially block the release of a lock.

```rust
pub fn example() -> i32 {
    let mutex = Mutex::new(1);
    let lock = mutex.lock().unwrap();
    let _ = *lock;
    let _ = *lock;
   do_heavy_computation_that_takes_time_and_returns_i32()
}
```

---

changelog: none
<!-- changelog_checked -->

0 files changed, 0 insertions, 0 deletions