ICE with associated types and default types

[carllerche]

#![feature(associated_types)]

pub trait Foo {
    type Bar = ();

    fn foo(&self);
}

impl Foo for String {
    fn foo(&self) {
        println!("FOO {}", self);
    }
}

pub fn main() {
    let s = "foo".to_string();
    s.foo();
}

$ rustc --version
rustc 0.13.0-nightly (c6c786671 2015-01-04 00:50:59 +0000)

$ rustc at.rs
at.rs:9:1: 13:2 error: internal compiler error: impl `VtableImpl(impl_def_id=DefId { krate: 0, node: 14 }:String.Foo, substs=Substs[types=[[];[];[]], regions=[[];[];[]]], nested=[[];[];[]])` did not contain projection for `Obligation(predicate=<collections::string::String as TraitRef(collections::string::String, Foo)>::Bar,depth=0)`
at.rs:9 impl Foo for String {
at.rs:10     fn foo(&self) {
at.rs:11         println!("FOO {}", self);
at.rs:12     }
at.rs:13 }
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libsyntax/diagnostic.rs:123

[huonw]

Very similar to #20347, but this has the additional factor of a default type for the associated type (hence I'm leaving it open).

[nikomatsakis]

Dup of #20347 (ICE) and #19476 (intended semantics for defaults)