src/test/ui/borrowck/borrowck-partial-reinit-4.rs

struct Test;

struct Test2(Option<Test>);

impl Drop for Test {
    fn drop(&mut self) {
        println!("dropping!");
    }
}

impl Drop for Test2 {
    fn drop(&mut self) {}
}

fn stuff() {
    let mut x : (Test2, Test2);
    (x.0).0 = Some(Test);
    //~^ ERROR assign of possibly-uninitialized variable: `x.0`
}

fn main() {
    stuff()
}