Internal compiler error upon deriving Debug for a generic type T with a default type argument that depends on T's lifetime parameter

[tenyoung795]

When you attempt to derive Debug for some T<'a, U: 'a = V<'a>>, the compiler throws Type parameter out of range when substituting in region 'a.

See this playpen. Note that this works fine on beta and nightly; perhaps this would make a good regression test case.

Code

#[derive(Debug)]
struct Message<'a, P: 'a = &'a [u8]> {
    header: &'a [u8],
    payload: P,
}

Error

bug.rs:1:10: 1:15 error: internal compiler error: Type parameter out of range when substituting in region 'a (root type=Some(&'a [u8])) (space=TypeSpace, index=0)
bug.rs:1 #[derive(Debug)]
                  ^~~~~
bug.rs:1:10: 1:15 note: in expansion of #[derive_Debug]
bug.rs:1:10: 1:15 note: expansion site

Meta

rustc --version --verbose

rustc 1.3.0 (9a92aaf19 2015-09-15)
binary: rustc
commit-hash: 9a92aaf19a64603b02b4130fe52958cc12488900
commit-date: 2015-09-15
host: x86_64-unknown-linux-gnu
release: 1.3.0

Backtrace

   1:     0x7f159a1288ee - sys::backtrace::write::haf6e4e635ac76143Ivs
   2:     0x7f159a130fd5 - panicking::on_panic::ha085a58a08f78856lzx
   3:     0x7f159a0f1bce - rt::unwind::begin_unwind_inner::hc90ee27246f12475C0w
   4:     0x7f15974f276c - rt::unwind::begin_unwind::h11988818671084554314
   5:     0x7f15974f270b - diagnostic::SpanHandler::span_bug::h5e275fd43fb4dbf5X6A
   6:     0x7f159824c67b - middle::subst::SubstFolder<'a, 'tcx>.TypeFolder<'tcx>::fold_region::h6e68580d67532a3aLlQ
   7:     0x7f159817b380 - middle::subst::SubstFolder<'a, 'tcx>.TypeFolder<'tcx>::fold_ty::h7f3a3205b864f389GnQ
   8:     0x7f15981f544c - middle::infer::InferCtxt<'a, 'tcx>::type_vars_for_defs::h26a1898fc01cd534AoC
   9:     0x7f1599877f4f - check::instantiate_path::h5cf0d5a86dc81128iIs
  10:     0x7f159987a6a3 - check::_match::check_pat_struct::h8307d8311228d69cbyb
  11:     0x7f159986c6a6 - check::_match::check_pat::h0d1b284bfff635dd43a
  12:     0x7f159987b59a - check::_match::check_match::h397d7cfcf63ba1eeIsb
  13:     0x7f1599921dce - check::check_expr_with_unifier::h2356985747389952917
  14:     0x7f15998f740f - check::check_block_with_expected::he8940408a5503b54Hhs
  15:     0x7f15998d7f3a - check::check_fn::h5e5df21b0fd773ea2In
  16:     0x7f15998ee4a6 - check::check_bare_fn::h86a03fb1f3983995Hyn
  17:     0x7f15998fd14c - check::check_method_body::h13d6362f0882c3dcSao
  18:     0x7f15998ec5c3 - check::check_item_body::hf589d5189d5cb836HYn
  19:     0x7f15998ee0d4 - check::check_item_types::h489a8e890fa40e75ewn
  20:     0x7f15999adafb - check_crate::h64d9b180d61a15fblaD
  21:     0x7f159a698479 - driver::phase_3_run_analysis_passes::closure.16545
  22:     0x7f159a696d91 - middle::ty::ctxt<'tcx>::create_and_enter::h17619121053301903364
  23:     0x7f159a691c71 - driver::phase_3_run_analysis_passes::h12169435128770927116
  24:     0x7f159a675d70 - driver::compile_input::h50576600c327a48aTba
  25:     0x7f159a75c083 - run_compiler::h08c4308e3023ae95A7b
  26:     0x7f159a759afe - boxed::F.FnBox<A>::call_box::h5719507417069443679
  27:     0x7f159a759429 - rt::unwind::try::try_fn::h17024725433081724618
  28:     0x7f159a130acd - __rust_try
  29:     0x7f159a11bb77 - rt::unwind::try::inner_try::h59523aa853a0e10avWw
  30:     0x7f159a759648 - boxed::F.FnBox<A>::call_box::h16487981074879516847
  31:     0x7f159a12fc11 - sys::thread::Thread::new::thread_start::h890d1188505773c835v
  32:     0x7f159477a181 - start_thread
  33:     0x7f1599d7e47c - __clone
  34:                0x0 - <unknown>