Use after free with mutable owned pointers

[evanw]

This code compiles and runs but seems to allow a use-after-free:

struct Foo {
  x: int
}

impl Drop for Foo {
  fn drop(&mut self) {
    println!("drop {}", self.x);
  }
}

fn main() {
  let mut ptr = ~Foo { x: 0 };
  let test = |foo: &Foo| {
    println!("access {}", foo.x);
    ptr = ~Foo { x: ptr.x + 1 };
    println!("access {}", foo.x);
  };
  test(ptr);
}

The output is:

access 0
drop 0
access 0
drop 1

This is with rustc 0.8. It may be related to #9853 but I'm not sure.

[thestinger]

cc @nikomatsakis

[ben0x539]

Maybe similar to #10398 too

[nikomatsakis]

This is #2202, I believe. I'll leave it open to verify.

[nikomatsakis]

More specifically fixed by #6801

[alexcrichton]

This has been fixed, flagging as needstest.