Add Mutex::into_inner()

[tomaka]

impl<T> Mutex<T> {
    pub fn into_inner(self) -> T {
         ...
    }
}

This is very useful for structures like this:

struct Foo {
     data: Mutex<Bar>
}

impl Foo {
    fn modify(&self) {
        self.data.lock().unwrap().modify();
    }

    fn consume(self) {
        let bar = self.data.into_inner();    // oops! doesn't exist
        bar.consume();
    }
}

[sfackler]

Seems like a pretty straightforward thing to add - I'm kind of surprised it's not there already.

[alexcrichton]

We may want into_inner to return LockResult<T>, but other than that I'd also be fine with this. We may also want to go a little further and add:

pub fn get_mut(&mut self) -> LockResult<&mut T>;

because if you have mutable access to a mutex there's no need for synchronization!

[cristicbz]

This is fixed by rust-lang/rust#29031 with rust-lang/rust#28968 as tracking issue for stabilization.

[alexcrichton]

Thanks @cristicbz!