Questionable type inference fail using complex generics and static methods

[brson]

Reduced from lmath. Note that I'm not sure whether this should work. Needs investigation.

fn main() {
    let id: &Mat2<float> = &Matrix::identity();
}

pub trait Index<Index,Result> { }
pub trait Dimensional<T>: Index<uint, T> { }

pub struct Mat2<T> { x: () }
pub struct Vec2<T> { x: () }

pub impl<T> Mat2<T>: Dimensional<Vec2<T>> { }
pub impl<T> Mat2<T>: Index<uint, Vec2<T>> { }

pub impl<T> Vec2<T>: Dimensional<T> { }
pub impl<T> Vec2<T>: Index<uint, T> { }

pub trait Matrix<T,V>: Dimensional<V> {
    static pure fn identity() -> self;
}

pub impl<T> Mat2<T>: Matrix<T, Vec2<T>> {
    static pure fn identity() -> Mat2<T> { fail }
}

/home/brian/dev/rust/src/test/run-pass/lmath.rs:2:26: 2:42 error: mismatched types: expected `@Index<uint,float>` but found `@Index<uint,Vec2<float>>` (expected float but found class Vec2)                         
/home/brian/dev/rust/src/test/run-pass/lmath.rs:2     let id: Mat2<float> = Matrix::identity();                                                                                                                      
                                                                            ^~~~~~~~~~~~~~~~                                                                                                                         
/home/brian/dev/rust/src/test/run-pass/lmath.rs:2:26: 2:42 error: mismatched types: expected `Vec2<float>` but found `float` (expected class Vec2 but found float)                                                   
/home/brian/dev/rust/src/test/run-pass/lmath.rs:2     let id: Mat2<float> = Matrix::identity();                                                                                                                      
                                                                            ^~~~~~~~~~~~~~~~    

[catamorphism]

Updated test case:

fn main() {
    let id: &Mat2<float> = &Matrix::identity();
}

pub trait Index<Index,Result> { }
pub trait Dimensional<T>: Index<uint, T> { }

pub struct Mat2<T> { x: () }
pub struct Vec2<T> { x: () }

impl<T> Dimensional<Vec2<T>> for Mat2<T> { }
impl<T> Index<uint, Vec2<T>> for Mat2<T> { }

impl<T> Dimensional<T> for Vec2<T> { }
impl<T> Index<uint, T> for Vec2<T> { }

pub trait Matrix<T,V>: Dimensional<V> {
    fn identity() -> Self;
}

impl<T> Matrix<T, Vec2<T>> for Mat2<T> {
    fn identity() -> Mat2<T> { fail!() }
}

I don't think this is critical for 0.6.

[catamorphism]

The test passes now; I'll check it in.

[catamorphism]

Can close when #6483 lands.

[catamorphism]

#6483 has failed twice now due to some unrelated Windows problem that I don't know how to address.

[catamorphism]

Test case added in b17b3f9