Rustc Stack overflow checking "cyclic" bounds in traits

[Ericson2314]

Minimal triggering program:

// any combo of Foo and Bar declarations crashes

trait Foo<A> where A: Bar<Self> {}
trait Bar<B> where B: Foo<Self> {}

//trait Foo<A: Bar<Self>> {}
//trait Bar<B: Foo<Self>> {}

// to avoid warning (but stack overflows after warning)
pub fn main() {}

Platform (though I doubt it matters):

# rustc --version
rustc 0.12.0-pre-nightly (ccae356ac 2014-09-12 23:30:54 +0000)
# uname -a    
Linux /*hostname*/ 3.2.0-4-amd64 #1 SMP Debian 3.2.60-1+deb7u3 x86_64 GNU/Linux

[huonw]

Dupe of issues like:

• Self-referential templated trait overflows the stack #15477
• Circular trait bounds causes stack overflow in rustc #12644
• cyclic trait inheritance leads to a rustc stack overflow #12511
• Stack overflow declaring mutually recursive traits #11824

Thanks for filing.