rust-clippy/tests/ui/significant_drop_tightening.rs

#![warn(clippy::significant_drop_tightening)]

use std::sync::Mutex;

pub fn complex_return_triggers_the_lint() -> i32 {
    fn foo() -> i32 {
        1
    }
    let mutex = Mutex::new(1);
    let lock = mutex.lock().unwrap();
    let _ = *lock;
    let _ = *lock;
    foo()
}

pub fn issue_10413() {
    let mutex = Mutex::new(Some(1));
    let opt = Some(1);
    if opt.is_some() {
        let lock = mutex.lock().unwrap();
        let _ = *lock;
        if opt.is_some() {
            let _ = *lock;
        }
    }
}

pub fn issue_11128() {
    use std::mem::drop as unlock;

    struct Foo {
        droppable: Option<Vec<i32>>,
        mutex: Mutex<Vec<i32>>,
    }

    impl Drop for Foo {
        fn drop(&mut self) {
            if let Some(droppable) = self.droppable.take() {
                let lock = self.mutex.lock().unwrap();
                let idx_opt = lock.iter().copied().find(|el| Some(el) == droppable.first());
                if let Some(idx) = idx_opt {
                    let local_droppable = vec![lock.first().copied().unwrap_or_default()];
                    unlock(lock);
                    drop(local_droppable);
                }
            }
        }
    }
}

pub fn issue_11160() -> bool {
    let mutex = Mutex::new(1i32);
    let lock = mutex.lock().unwrap();
    let _ = lock.abs();
    true
}

pub fn issue_11189() {
    struct Number {
        pub value: u32,
    }

    fn do_something() -> Result<(), ()> {
        let number = Mutex::new(Number { value: 1 });
        let number2 = Mutex::new(Number { value: 2 });
        let number3 = Mutex::new(Number { value: 3 });
        let mut lock = number.lock().unwrap();
        let mut lock2 = number2.lock().unwrap();
        let mut lock3 = number3.lock().unwrap();
        lock.value += 1;
        lock2.value += 1;
        lock3.value += 1;
        drop((lock, lock2, lock3));
        Ok(())
    }
}

pub fn path_return_can_be_ignored() -> i32 {
    let mutex = Mutex::new(1);
    let lock = mutex.lock().unwrap();
    let rslt = *lock;
    let _ = *lock;
    rslt
}

pub fn post_bindings_can_be_ignored() {
    let mutex = Mutex::new(1);
    let lock = mutex.lock().unwrap();
    let rslt = *lock;
    let another = rslt;
    let _ = another;
}

pub fn unnecessary_contention_with_multiple_owned_results() {
    {
        let mutex = Mutex::new(1i32);
        let lock = mutex.lock().unwrap();
        let _ = lock.abs();
        let _ = lock.is_positive();
    }

    {
        let mutex = Mutex::new(1i32);
        let lock = mutex.lock().unwrap();
        let rslt0 = lock.abs();
        let rslt1 = lock.is_positive();
        do_heavy_computation_that_takes_time((rslt0, rslt1));
    }
}

pub fn unnecessary_contention_with_single_owned_results() {
    {
        let mutex = Mutex::new(1i32);
        let lock = mutex.lock().unwrap();
        let _ = lock.abs();
    }
    {
        let mutex = Mutex::new(vec![1i32]);
        let mut lock = mutex.lock().unwrap();
        lock.clear();
    }

    {
        let mutex = Mutex::new(1i32);
        let lock = mutex.lock().unwrap();
        let rslt0 = lock.abs();
        do_heavy_computation_that_takes_time(rslt0);
    }
    {
        let mutex = Mutex::new(vec![1i32]);
        let mut lock = mutex.lock().unwrap();
        lock.clear();
        do_heavy_computation_that_takes_time(());
    }
}

// Marker used for illustration purposes.
pub fn do_heavy_computation_that_takes_time<T>(_: T) {}

fn main() {}