[Nightly 1.4.0-4f33e43cb 2015-08-05] Compiler panic when mis-using Zero trait

[lightsfury]

Attempting to misuse a trait can cause a compiler panic. The offending code is a simplified version of what I was working on.

I tried this code:

fn rem_is_zero<T: Eq + Rem + Zero>(n: T, m: T) -> bool
  where <T as Rem>::Output: Zero + Eq
{
  let z = <T as Rem>::Output::zero(); // Compiler panic
  //let z = <<T as Rem>::Output as Zero>::zero(); // Compiles correctly

  (n % m) == z
}

After reviewing the documentation, I expect this to throw a syntax error. Specifically, because the let RHS should be written as: <<T as Rem>::Output as Zero>::zero. This code does compile and work as expected.

I don't know if this is specific to the Zero trait as I was able to use it like this:

fn eq_zero<T:Eq + Zero>(n: T) -> bool
{
  let z = T::zero();

  n == z
}

Meta

rustc --version --verbose:

rustc 1.4.0-nightly (4f33e43cb 2015-08-05)
binary: rustc
commit-hash: 4f33e43cbceb60ec85bb5140bd5470965ea92d16
commit-date: 2015-08-05
host: x86_64-pc-windows-gnu
release: 1.4.0-nightly

Backtrace:

C:\Stuff\Programming\rust-tut\rust-nightly-bug\src>rustc main.rs
main.rs:18:11: 18:35 error: internal compiler error: Type parameter `Self/SelfSpace.0` (Self/SelfSpace/0) out of range when substituting (root type=Some(Self)) substs=Substs[types=[[];[];[]], regions=[[];[];[]]]
main.rs:18   let z = <T as Rem>::Output::zero();
                     ^~~~~~~~~~~~~~~~~~~~~~~~
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
thread 'rustc' panicked at 'Box<Any>', ../src/libsyntax\diagnostic.rs:176

stack backtrace:
   1:         0x699b9ce8 - sys::backtrace::write::h681b474c6c2394f4tNs
   2:         0x699c37ff - rt::unwind::register::hb538ab914c4328d5b2w
   3:         0x699854df - rt::unwind::begin_unwind_inner::hb80fd8ef51b4060akZw
   4:         0x7105ee5b - diagnostic::SpanHandler::span_bug::hc633dbf01b525dc5X6A
   5:         0x7105ee13 - diagnostic::SpanHandler::span_bug::hc633dbf01b525dc5X6A
   6:         0x692b88d8 - middle::subst::SubstFolder<'a, 'tcx>.TypeFolder<'tcx>::fold_ty::hca42f6dc71385de0GnQ
   7:         0x670f83d1 - check::FnCtxt<'a, 'tcx>.AstConv<'tcx>::ty_infer::hb1193da908738887xBo
   8:         0x6716d690 - rscope::ShiftedRscope<'r>.RegionScope::anon_regions::h419ad07efdb37e6bUlu
   9:         0x671752b2 - astconv::PathParamMode...std..cmp..PartialEq::ne::h94fa3bff02dd36c9OIu
  10:         0x67174689 - astconv::PathParamMode...std..cmp..PartialEq::ne::h94fa3bff02dd36c9OIu
  11:         0x6717a6cc - astconv::PathParamMode...std..cmp..PartialEq::ne::h94fa3bff02dd36c9OIu
  12:         0x671630d8 - check::TupleArgumentsFlag...std..clone..Clone::clone::hedb38ea352ace7f6cBq
  13:         0x67091969 - check::resolve_ty_and_def_ufcs::h0db529947a54cd24X2r
  14:         0x6715813b - check::may_break::he5881651fb8999a1eut
  15:         0x670f995e - check::FnCtxt<'a, 'tcx>.AstConv<'tcx>::projected_ty::h759a827f017a8a8atDo
  16:         0x67141285 - check::may_break::he5881651fb8999a1eut
  17:         0x67166240 - check::check_decl_initializer::hf0aa92b366271b1awas
  18:         0x671662da - check::check_decl_local::h37a43869df125d9bKbs
  19:         0x671664bf - check::check_stmt::h5078de71b85f2dc0Dds
  20:         0x671182fb - check::GatherLocalsVisitor<'a, 'tcx>.Visitor<'tcx>::visit_item::h6ba246b1c9f3850dKIn
  21:         0x670f920a - check::FnCtxt<'a, 'tcx>.AstConv<'tcx>::projected_ty::h759a827f017a8a8atDo
  22:         0x6710fa3c - check::check_item_types::h3739f0f18758ac32ewn
  23:         0x6710dcf0 - check::check_item_body::hc85a464b96f40859HYn
  24:         0x6710f684 - check::check_item_types::h3739f0f18758ac32ewn
  25:         0x671c8634 - check_crate::ha45cf61934d4de29laD
  26:         0x67be60dc - driver::assign_node_ids_and_map::h4dcd00430a00f2727Da
  27:         0x67be47f4 - driver::assign_node_ids_and_map::h4dcd00430a00f2727Da
  28:         0x67bdef86 - driver::assign_node_ids_and_map::h4dcd00430a00f2727Da
  29:         0x67bc2472 - driver::compile_input::h456239a0987e1d55Tba
  30:         0x67caa553 - run_compiler::ha97eef431fa5768cC7b
  31:         0x67ca8407 - run::h1e382076a350f7f7i7b
  32:         0x67ca7da9 - run::h1e382076a350f7f7i7b
  33:         0x699c318c - rt::unwind::imp::rust_eh_personality_catch::h8647fb0995b90ac0TMw
  34:         0x699ad7e2 - rt::unwind::try::inner_try::haade0eef5e14ff2ddVw
  35:         0x67ca7f77 - run::h1e382076a350f7f7i7b
  36:         0x699c157e - sys::process::Command::cwd::h322b10c2248cc4393Ev
  37:     0x7fffae6d2d92 - BaseThreadInitThunk

[arielb1]

duplicate of #28344

[brson]

This was reportedly a 1.3 regression. Fixed in 1.4.