ICE: the type of this value must be known in this context

[mason-larobina]

While fiddling with some code I stumbled upon an internal compiler error with the following:
https://gist.github.com/mason-larobina/9e7dd78e4b605329800c

Here is the backtrace:

~/src/rust-sudoku$ RUST_BACKTRACE=1 cargo test                                                                                                                                                       
   Compiling rust-sudoku v0.0.1 (file:///usr/local/google/home/masonl/src/rust-sudoku)
src/main.rs:28:9: 28:11 error: mismatched types:
 expected `Point`,
    found `&_`
(expected struct `Point`,
    found &-ptr) [E0308]
src/main.rs:28     let &p = update.point;
                       ^~
src/main.rs:29:16: 29:19 error: the type of this value must be known in this context
src/main.rs:29     self.cells[p.y][p.x] = update.value;
                              ^~~
error: internal compiler error: no type for expr in fcx 0x7f481bbecfb0
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/beta-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:190

stack backtrace:
   1:     0x7f48239e23c8 - sys::backtrace::write::h179e141147f9ee14IJC
   2:     0x7f4823a0d770 - panicking::on_panic::h6aa569d33389f0cfsXI
   3:     0x7f48239454a3 - rt::unwind::begin_unwind_inner::h082f07869f4b9731ACI
   4:     0x7f4820ce904d - rt::unwind::begin_unwind::h13428428822164950735
   5:     0x7f4820ce97a2 - diagnostic::Handler::bug::h7dec5f2940917255ZsB
   6:     0x7f48216fc82b - session::Session::bug::hc743ab3e9fbf0b0bnYq
   7:     0x7f482260a9e7 - check::FnCtxt<'a, 'tcx>::expr_ty::hbdbb2c3d06403ae1qwp
   8:     0x7f4822627e77 - check::writeback::WritebackCx<'cx, 'tcx>.Visitor<'v>::visit_expr::hadfaa727ac46dd801bc
   9:     0x7f4822628227 - check::writeback::WritebackCx<'cx, 'tcx>.Visitor<'v>::visit_expr::hadfaa727ac46dd801bc
  10:     0x7f4822628813 - check::writeback::WritebackCx<'cx, 'tcx>.Visitor<'v>::visit_expr::hadfaa727ac46dd801bc
  11:     0x7f48226e2c4a - check::check_bare_fn::hb43e600383cf2ee2UQn
  12:     0x7f48226e82f9 - check::check_method_body::h033e5d461fd87166Koo
  13:     0x7f48226dfd94 - check::check_item::h77d9b4d4612f23cfF9n
  14:     0x7f48227b4a96 - check_crate::closure.36300
  15:     0x7f48227aee73 - check_crate::h4b0848761f18a2bcbwC
  16:     0x7f48240615cd - driver::phase_3_run_analysis_passes::hf7cad4098b28ceb1gGa
  17:     0x7f4824045425 - driver::compile_input::h7c62c2870ff901f6Qba
  18:     0x7f48240fca25 - run_compiler::hc815b49ce638c28eV4b
  19:     0x7f48240fa33d - boxed::F.FnBox<A>::call_box::h4290333406520961126
  20:     0x7f48240f9879 - rt::unwind::try::try_fn::h13999576404798567721
  21:     0x7f4823a89c68 - rust_try_inner
  22:     0x7f4823a89c55 - rust_try
  23:     0x7f48240f9b4b - boxed::F.FnBox<A>::call_box::h14489442628055152240
  24:     0x7f48239f8781 - sys::thread::create::thread_start::h02b7da32b4d7a4aaExH
  25:     0x7f481d7c7181 - start_thread
  26:     0x7f48235a847c - __clone
  27:                0x0 - <unknown>

[arielb1]

Minified:

fn main() {
    1.create_a_type_error[()+()];
}

[arielb1]

I think the problem is the rather interesting match in writeback.rs:123. cc @nikomatsakis.

[arielb1]

I mean, it says "Hacky Hack".