Dereferencing of mutable &mut paths found in borrowed paths should not be permitted

[nikomatsakis]

In particular this program ought to be illegal:

struct S<'self> {
    pointer: &'self mut int
}

fn copy_borrowed_ptr2<'a>(p: &'a mut S<'a>) -> S<'a> {
    S { pointer: &mut *p.pointer }
}

fn main() {
    let mut x = 1;

    {
        let mut y = S { pointer: &mut x };
        let z = copy_borrowed_ptr2(&mut y);
        *y.pointer += 1; // ERROR EXPECTED HERE
        *z.pointer += 1;
    }
}

See also #8624

[metajack]

nominating production ready

[bblum]

this should only be illegal for writes, right? reading a dereference of same seems still legal.

[nikomatsakis]

On Mon, Aug 19, 2013 at 05:03:45PM -0700, Ben Blum wrote:

this should only be illegal for writes, right? reading a dereference of same seems still legal.

That is correct, reads are always legal.