Type inference works with method calls, but not with UFCS

[japaric]

STR

use std::u8;

trait IntoIterator {
    type Iter: Iterator;

    fn into_iter(self) -> Self::Iter;
}

impl<I> IntoIterator for I where I: Iterator {
    type Iter = I;

    fn into_iter(self) -> I {
        self
    }
}

fn old_for_loop(byte: u8) -> u8 {
    let mut result = 0;
    for i in range(0, u8::BITS) {
        result |= ((byte >> i) & 1) << (u8::BITS - 1 - i);
    }
    result
}

fn desugared_for_loop_bad(byte: u8) -> u8 {
    let mut result = 0;
    match IntoIterator::into_iter(range(0, u8::BITS)) {
        mut iter => {
            loop {
                match ::std::iter::Iterator::next(&mut iter) {
                    ::std::option::Option::Some(i) => {
                        result |= ((byte >> i) & 1) << (u8::BITS - 1 - i);
                        //~^ error: right-hand-side of a shift operation must have integral type, not `_`
                    },
                    ::std::option::Option::None => break
                }
            }
        }
    }
    result
}

fn desugared_for_loop_good(byte: u8) -> u8 {
    let mut result = 0;
    match range(0, u8::BITS).into_iter() {  // NB method call instead of UFCS
        mut iter => {
            loop {
                match ::std::iter::Iterator::next(&mut iter) {
                    ::std::option::Option::Some(i) => {
                        result |= ((byte >> i) & 1) << (u8::BITS - 1 - i);
                    },
                    ::std::option::Option::None => break
                }
            }
        }
    }
    result
}

fn main() {}

use std::ptr;

trait IntoIterator {
    type Iter: Iterator;

    fn into_iter(self) -> Self::Iter;
}

impl<I> IntoIterator for I where I: Iterator {
    type Iter = I;

    fn into_iter(self) -> I {
        self
    }
}

fn old_for_loop<T>(v: Vec<T>) {
    for x in v.iter() {
        unsafe { ptr::read(x); }
    }
}

fn desugared_for_loop_bad<T>(v: Vec<T>) {
    match IntoIterator::into_iter(v.iter()) {
        mut iter => {
            loop {
                match ::std::iter::Iterator::next(&mut iter) {
                    ::std::option::Option::Some(x) => {
                        unsafe { ptr::read(x); }
//~^ error: type mismatch resolving `<core::slice::Iter<'_, T> as core::iter::Iterator>::Item == *const _`: expected &-ptr, found *-ptr
                    },
                    ::std::option::Option::None => break
                }
            }
        }
    }
}

fn desugared_for_loop_good<T>(v: Vec<T>) {
    match v.iter().into_iter() {  // NB method call instead of UFCS
        mut iter => {
            loop {
                match ::std::iter::Iterator::next(&mut iter) {
                    ::std::option::Option::Some(x) => {
                        unsafe { ptr::read(x); }
                    },
                    ::std::option::Option::None => break
                }
            }
        }
    }
}

fn main() {}

Type inference works fine with method calls (into_iter()), but fails with UFCS (IntoIterator::into_iter()).

Version

rustc 1.0.0-nightly (8903c21d6 2015-01-15 22:42:58 +0000)

This is blocking migration to the new for loops (#20790).

cc @nikomatsakis