ICE when not constraining associated type of a trait object

[elinorbgr]

Shortest code:

trait Foo {
    type Bar;
    fn foo(&self) -> Self::Bar;
}

fn next(i: &Foo) {
    let _ = i.foo();
}

fn main() {}

produces this output on playpen (rustc 1.0.0-nightly (b4c965ee8 2015-03-02) (built 2015-03-03) according to playbot):

<anon>:7:1: 9:2 warning: function is never used: `next`, #[warn(dead_code)] on by default
<anon>:7 fn next(i: &Foo) {
<anon>:8     let _ = i.foo();
<anon>:9 }
error: internal compiler error: fictitious type <Foo as Foo>::Bar in sizing_type_of()
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:189

My local rustc seems to not be able to produce backtraces, sorry.

[frewsxcv]

When compiling the original codeblock with Rust 1.0 beta 2:

~/Downloads $ rustc test.rs
test.rs:8:13: 8:16 error: the value of the associated type `Bar` (from the trait `Foo`) must be specified [E0191]
test.rs:8 fn next(i: &Foo) {
                      ^~~
error: aborting due to previous error

I no longer get an ICE.

[elinorbgr]

No longer an ICE, it now triggers E0191.