ICE: None != Some(()) with method call on unknown type

[huonw]

fn main() {
    [].sort_by(| a, b | a.partial_cmp(b))
}

ice5.rs:2:27: 2:41 error: the type of this value must be known in this context
ice5.rs:2     [].sort_by(| a, b | a.partial_cmp(b))
                                    ^~~~~~~~~~~~~~
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
task 'rustc' panicked at 'assertion failed: `(left == right) && (right == left)` (left: `None`, right: `Some(())`)', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/middle/typeck/check/method/confirm.rs:152

[barosl]

The ICE seems to be caused by a bug in auto-dereferencing. Taking the following code as an example,

[].split(|x| x.clone()); // This code causes an ICE, but
[].split(|&x| x.clone()); // This code doesn't cause an ICE

This should be fixed by #19813.

[swgillespie]

I've got another repro of what looks to be the same issue, if it's helpful. Moving the &mut on line 9 to its correct location in front of fmt::Formatter doesn't ICE.

Code: https://gist.github.com/swgillespie/a1c7bf117f2fadfd2504
Output: https://gist.github.com/swgillespie/bb5e353c6a14eee3b193