ICE: rustc overflows its stack on instanciation of enum

[abandoned-cocoon]

Also available at http://is.gd/7glmKz

pub trait Paramters { type SelfRef; }

struct RP<'a> { _marker: std::marker::PhantomData<&'a ()> }
struct BP;

impl<'a> Paramters for RP<'a> { type SelfRef = &'a X<RP<'a>>; }
impl Paramters for BP { type SelfRef = Box<X<BP>>; }

pub struct Y;
pub enum X<P: Paramters> {
    Nothing,
    SameAgain(P::SelfRef, Y)
}

fn main() {
    // fine
    let bnil: Box<X<BP>> = Box::new(X::Nothing);
    let bx: Box<X<BP>> = Box::new(X::SameAgain(bnil, Y));
    // crashes rustc
    let rnil: X<RP> = X::Nothing;
    let rx: X<RP> = X::SameAgain(&rnil, Y);
}

Output:

thread 'rustc' has overflowed its stack
Illegal instruction (core dumped)

[eddyb]

This seems to enter a recursive cycle in middle::implicator::Implicator:

accumulate_from_ty
accumulate_from_adt
accumulate_from_assoc_types
accumulate_from_ty

@nikomatsakis Should the implicator detect cycles and report them, or even let this code compile?

[steveklabnik]

This needs a test, and no longer ICEs, but looks like @apasel422 is on it!