Destructuring Droppable structs

language design
16

FWIW, it's already possible to define a helper macro for this task:

struct Point { x: i32, y: i32 }

impl Drop for Point {
    fn drop(&mut self) {
        unreachable!()
    }
}

let p = Point { x: 42, y: 27 };
destructuring_drop! {
    let Point {
        x: value,
        y: _,
    } = p;
}
assert_eq!(dbg!(value), 42);

By having the macro expand to the following unsafe code:

let (value, _) = match *ManuallyDrop::new(p) {
    Point { ref x, ref y } => unsafe {
        (
            <*const _>::read(x),
            <*const _>::read(y),
        )
    },
};

Having the hard error become a lint (I don't care about its default polarity) seems like a less cumbersome and with-better-diagnostics way to achieve the same :slightly_smiling_face:

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