Closed
Description
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