ICE when using a lifetime parameter in a where clause

[sfackler]

fn foo<'a, I>(mut it: I) where I: Iterator<&'a int> {}

fn main() {
    foo([1i, 2].iter());
}

test.rs:4:5: 4:8 error: internal compiler error: cannot relate bound region: ReLateBound(4, BrNamed(syntax::ast::DefId{krate: 0u32, node: 11u32}, 'a)) <= ReInfer(102)
test.rs:4     foo([1i, 2].iter());
              ^~~
note: the compiler hit an unexpected failure path. 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' failed at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/libsyntax/ast_util.rs:791

stack backtrace:
   1:     0x7f0750d2ba60 - rt::backtrace::imp::write::h915f70b87af05b8cmxr
   2:     0x7f0750d2eb00 - failure::on_fail::h3bfbb66e809f10e63Sr
   3:     0x7f0751505ee0 - unwind::begin_unwind_inner::hdda436f89ca4acd6Zhe
   4:     0x7f074f9450b0 - unwind::begin_unwind::h9125269610435311192
   5:     0x7f074f945000 - diagnostic::SpanHandler::span_bug::hc244fe505535bd433uF
   6:     0x7f0751abd6d0 - driver::session::Session::span_bug::h5df75a538dc01b06ZNA
   7:     0x7f0751f97630 - middle::typeck::infer::region_inference::RegionVarBindings<'a>::make_subregion::h966bcd69e331f8c59W5
   8:     0x7f0751f7d890 - middle::typeck::infer::sub::Sub<'f>.Combine::regions::h03568e631b5674497r8
   9:     0x7f0751f7dc00 - middle::typeck::infer::sub::Sub<'f>.Combine::contraregions::h13956ce561fb5850xr8
  10:     0x7f0751f675a0 - middle::typeck::infer::sub::Sub<'f>.Combine::tys::h8728d19bb6506359xA8
  11:     0x7f0751fabfb0 - middle::typeck::infer::combine::eq_tys::closure.125549
  12:     0x7f0751f64bf0 - middle::typeck::infer::InferCtxt<'a>::try::h8077952307852343475
  13:     0x7f0751fabe30 - middle::typeck::infer::combine::eq_tys::h14537646206334856932
  14:     0x7f0751faa200 - middle::typeck::infer::combine::Combine::substs::h4709403821174409647
  15:     0x7f0751fd6b80 - middle::typeck::infer::mk_sub_trait_refs::closure.126315
  16:     0x7f0751fd68b0 - middle::typeck::infer::InferCtxt<'a>::commit_if_ok::closure.126307
  17:     0x7f0751fd6700 - middle::typeck::infer::InferCtxt<'a>::commit_unconditionally::h4157984422034910170
  18:     0x7f0751e5a3b0 - middle::typeck::infer::mk_sub_trait_refs::hee6f3e0ab4e569e6bxd
  19:     0x7f0751e59d40 - middle::typeck::check::vtable::relate_trait_refs::hf00ee302275f83ffaJL
  20:     0x7f0751e5b050 - middle::typeck::check::vtable::search_for_vtable::h62cb709e3558328eo1L
  21:     0x7f0751e58160 - middle::typeck::check::vtable::lookup_vtables_for_param::closure.121712
  22:     0x7f0751e1d090 - middle::ty::each_bound_trait_and_supertraits::hf6aa2b1412717287BOI
  23:     0x7f0751e57be0 - middle::typeck::check::vtable::lookup_vtables_for_param::h2f3e3aa0d87321fcEuL
  24:     0x7f0751e55a20 - middle::typeck::check::vtable::lookup_vtables::h2b52d443aea8bc88GoL
  25:     0x7f0751e65650 - middle::typeck::check::vtable::early_resolve_expr::closure.121862
  26:     0x7f0751e654c0 - middle::typeck::check::FnCtxt<'a>::opt_node_ty_substs::h73a61f1da9fe6172PXU
  27:     0x7f0751e61970 - middle::typeck::check::vtable::early_resolve_expr::h74a603ae5b2dd414lnM
  28:     0x7f0751f002c0 - middle::typeck::check::check_argument_types::ha6ecc6e8415348b0xmV
  29:     0x7f0751f02960 - middle::typeck::check::check_expr_with_unifier::h7f07d1d05896e44fSXV
  30:     0x7f0751f616a0 - middle::typeck::check::check_stmt::h139e8f1cea959a0502X
  31:     0x7f0751ecb610 - middle::typeck::check::check_block_with_expected::h32b2d067c318c94ad7X
  32:     0x7f0751ec73a0 - middle::typeck::check::check_fn::h11b95bd8147ec11f3dT
  33:     0x7f0751ec70c0 - middle::typeck::check::check_bare_fn::h0b6077c308262260I2S
  34:     0x7f0751ec0220 - middle::typeck::check::check_item::habadeb79d560f4d0QBT
  35:     0x7f0751ec6ec0 - middle::typeck::check::check_item_types::h63a60aa7829eefedZ1S
  36:     0x7f07518df300 - util::common::time::h2328891505148832078
  37:     0x7f07520d4b50 - middle::typeck::check_crate::h266f9d5cd5ece381vFk
  38:     0x7f07521a2180 - driver::driver::phase_3_run_analysis_passes::h53949348bfafe8ffJfz
  39:     0x7f075219d2c0 - driver::driver::compile_input::hd2d14ec13437de9cP1y
  40:     0x7f075224a150 - driver::run_compiler::he03a385a4310d17aJzC
  41:     0x7f075224a060 - driver::main_args::closure.137214
  42:     0x7f075225ca30 - task::TaskBuilder<S>::try_future::closure.138375
  43:     0x7f075225c830 - task::TaskBuilder<S>::spawn_internal::closure.138352
  44:     0x7f0752cabb30 - task::spawn_opts::closure.8325
  45:     0x7f075155df70 - rust_try_inner
  46:     0x7f075155df60 - rust_try
  47:     0x7f0751503540 - unwind::try::hc4ccde5733fe2f0cf6d
  48:     0x7f07515032e0 - task::Task::run::h4d1bcb29f70db0c3xcd
  49:     0x7f0752cab8f0 - task::spawn_opts::closure.8271
  50:     0x7f0751505120 - thread::thread_start::h8729f7243e18bd84jBd
  51:     0x7f07507bb060 - start_thread
  52:     0x7f07511d4489 - __clone
  53:                0x0 - <unknown>

changing foo to use the old syntax allows the program to compile:

fn foo<'a, I: Iterator<&'a int>>(mut it: I) {}

fn main() {
    foo([1i, 2].iter());
}

[sfackler]

cc @pcwalton

[japaric]

I think this is similar to #16549