ICE when returning struct with borrowed pointer to trait

[ghost]

A function which takes a borrowed pointer to a trait and returns a struct with that borrowed pointer results in an ICE:

trait Inner {
    fn print(&self);
}

impl Inner for int {
    fn print(&self) { io::print(fmt!("Inner: %d\n", *self)); }
}

struct Outer<'self> {
    inner: &'self Inner
}

impl<'self> Outer<'self> {
    fn new<'r>(inner: &'r Inner) -> Outer<'r> {
        Outer {
            inner: inner
        }
    }
}

fn main() {
    let inner = 5;
    let outer = Outer::new(&inner as &Inner);
    outer.inner.print();
}

This is the resulting ICE:

borrowtest-4.rs:16:19: 16:24 error: internal compiler error: Cannot relate bound region as subregion: br_self
borrowtest-4.rs:16             inner: inner

This does not occur with concrete types, only with borrowed pointers to traits.

[catamorphism]

Reproduced as of 0252c30 -- nominating for milestone 5, production-ready

[bblum]

@zargony found a simpler test: https://gist.github.com/zargony/1780399775004b28f0b4

Oddly this one works fine if you remove the type parameter.

[zargony]

Here's another case that seems to trigger the same ICE. Both methods result in the ICE: Cannot relate bound region as subregion: br_self. Seems to be related to the type parameter, since everything compiles fine if you remove from MyTrait.

trait MyTrait<T> { }

struct MyContainer<'self, T> {
    elems: ~[&'self MyTrait<T>],
}

impl<'self, T> MyContainer<'self, T> {
    fn foo (&self, f: &fn (&'self MyTrait<T>)) {
        f(self.elems[0]);
    }
    fn bar (&self) -> &'self MyTrait<T> {
        self.elems[0]
    }
}

fn main () {}

[mstewartgallus]

Ugh, I ran into this bug while trying to re-factor extra::arc. +1 internet points towards whoever fixes this.

[jmgrosen]

It would be very nice if this were fixed, not sure how to do what I'm doing without it.

[graydon]

accepted for production-ready milestone

[nikomatsakis]

I will try to take a look at this soon

[alexcrichton]

This appears to work now, flagging as needstest