Move out of deref for `ManuallyDrop`

language design
9

I am not 100% certain what is going on in your example, but what I intend is:

struct Foo(String, String);

impl Drop for Foo {
    fn drop(&mut self) {}
}

let foo = Foo("a".to_owned(), "b".to_owned());
let manual = ManuallyDrop::new(foo);
let a = manual.0; // Partial move