ICE when returning a local unwrapped dvec inside an impl

[erickt]

This code should be rejected outright since I'm trying to move a dvec out of a record without consuming the record, but it's ICEing instead of a proper error message:

import dvec::dvec;

type parser = {
    tokens: dvec<int>,
};

impl parser for parser {
    fn parse() -> [mut int] {
        dvec::unwrap(self.tokens)
    }
}

Returns:

./mustache.rs:9:21: 9:25 error: internal compiler error: illegal reader (lnk_exit) for `vk_self`
./mustache.rs:9         dvec::unwrap(self.tokens)