New ICE from old minimal example code: Uninferred types/regions in `_`

[solson]

I previously minimized the ICE-causing code in #27954, and the original code is now fixed, but my minimized code now ICEs with a new error.

Code:

playpen

pub trait Foo {
    type Bar;
}

pub trait Broken {
    type Assoc;
    fn broken(&self) where Self::Assoc: Foo;
}

impl<T> Broken for T {
    type Assoc = ();
    fn broken(&self) where Self::Assoc: Foo {
        let _x: <Self::Assoc as Foo>::Bar;
    }
}

fn main() { 
    let _m: &Broken<Assoc=()> = &();
}

Error:

rustc 1.13.0-nightly (a059cb2f3 2016-09-27)
error: internal compiler error: ../src/librustc/infer/mod.rs:697: Uninferred types/regions in `_`

[Mark-Simulacrum]

I don't get an ICE today; marking as E-needstest.