ICE: function returning `UnfoldrIterator`

[gifnksm]

The following code causes ICE.

use core::iterator::{ UnfoldrIterator };

pub fn uint_range(start: uint, end: uint, step: int) -> UnfoldrIterator<uint, (uint, int)>
{
    fn next(st: &mut (uint, int)) -> Option<(uint, int)> {
        None
    }

    return UnfoldrIterator::new(next, (start, step));
}

$ rustc  foldr.rs
error: internal compiler error: ty::Region#subst(): Reference to self region when given substs with no self region: substs(self_r=None, self_ty=None, tps=[<V3>,<V4>])

rustc seems to fail to suggest 'self region of UnfoldrIterator<'self>,
but I don't know the appropriate region name for this case.

[yichoi]

current code cannot be compiled

foldr.rs:11:11: 11:53 error: mismatched types: expected `std::iterator::UnfoldrIterator<,uint,(uint,int)>` but found `std::iterator::UnfoldrIterator<,(uint,int),(uint,int)>` (expected uint but found tuple)
foldr.rs:11     return UnfoldrIterator::new(next, (start, step));
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
error: aborting due to previous error

if fn next changed like below, it can be compiled without ICE

fn next(st: &mut (uint, int)) -> Option<uint> {
    None
}

It looks to me not a issue.