ICE: impl Foo for [u8; usize::BYTES]

[benw]

I tried this code:

pub trait Foo {}
impl Foo for [u8; usize::BYTES] {}

I expected to see this happen: great success

Instead, this happened: error: internal compiler error: unexpected panic

Meta

rustc --version --verbose:

rustc 1.4.0-nightly (6873b9fee 2015-09-13)
binary: rustc
commit-hash: 6873b9fee4af732fe81d54fdcedbd31201e3edf0
commit-date: 2015-09-13
host: x86_64-apple-darwin
release: 1.4.0-nightly

Backtrace:

error: internal compiler error: unexpected panic
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 'path not fully resolved: PathResolution { base_def: DefPrimTy(TyUint(usize)), last_private: LastMod(AllPublic), depth: 1 }', ../src/librustc/middle/def.rs:82

stack backtrace:
   1:        0x1121128d0 - sys::backtrace::tracing::imp::write::heea627b667abca63Y3s
   2:        0x11210fcfb - panicking::on_panic::hdbb29ca470ba8d91wSw
   3:        0x1120da292 - sys_common::unwind::begin_unwind_inner::h96272d8b0ab240cfv6r
   4:        0x1120dad6d - sys_common::unwind::begin_unwind_fmt::h9afcfd3cbded904aB5r
   5:        0x10ed9d260 - middle::const_eval::eval_const_expr_partial::h09b300ea76947f73LTk
   6:        0x10e87b052 - astconv::ast_ty_to_ty::hea6c277082e3ec36Hjx
   7:        0x10e8d365b - collect::convert_item::had78e6f690b64d6668y
   8:        0x10e8cf086 - collect::collect_item_types::h0cdd1ad21711c8b7Cky
   9:        0x10e91b84d - check_crate::hec1ce520a39b9d455BE
  10:        0x10e08f9ea - driver::phase_3_run_analysis_passes::closure.21862
  11:        0x10e07162a - middle::ty::ctxt<'tcx>::create_and_enter::h16774090565533553846
  12:        0x10e06ce35 - driver::phase_3_run_analysis_passes::h7058980529217618503
  13:        0x10e04d825 - driver::compile_input::hb180f9b5439d25130ba
  14:        0x10e1b22a0 - run_compiler::hed85d66f90e035a8qqc
  15:        0x10e1afb99 - boxed::F.FnBox<A>::call_box::h2035540886510390739
  16:        0x10e1af592 - sys_common::unwind::try::try_fn::h1377311635092239657
  17:        0x11210f638 - __rust_try
  18:        0x112103c60 - sys_common::unwind::try::inner_try::hcc9e69ddf677c559T2r
  19:        0x10e1af742 - boxed::F.FnBox<A>::call_box::h6878960542759305751
  20:        0x1121185dd - sys::thread::Thread::new::thread_start::h149e6b462b5fd2cfpqw
  21:     0x7fff99141059 - _pthread_body
  22:     0x7fff99140fd6 - _pthread_start

[bluss]

It will compile if you add this:

#![feature(num_bits_bytes)]
use std::usize;

This turns usize::BYTES into a regular path -> const lookup instead of an associated const. (Associated const usize::BYTES does not exist, by the way).

But it's still a good bug report, don't close it!

[bluss]

Similar to issue #24947.

Another test-case:

struct FixedArray<T, ArraySize> { data: [T; ArraySize::Size] }

fn main() {}

with

rustc 1.5.0-dev (ecbd8c3b4 2015-09-22)
binary: rustc
commit-hash: ecbd8c3b43d7d992938f7214b3bab1c017669e59
commit-date: 2015-09-22
host: x86_64-unknown-linux-gnu
release: 1.5.0-dev

results of rustc main.rs :

error: internal compiler error: unexpected panic
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 'no path elem for NodeTyParam(TyParam { ident: ArraySize#0, id: 10, bounds: [], default: None, span: main.rs:2:22: 2:31 })', src/librustc/front/map/mod.rs:488

results of RUST_BACKTRACE=1 rustc main.rs:

Segmentation fault (core dumped)

with backtrace from gdb - similar to the stack backtrace reported in this issue:

#0  0x0000000000001000 in ?? ()
#1  0x00007f36a58f567a in backtrace_pcinfo (state=0x7f36a6359000, pc=139872682138457, 
    callback=0x7f36a5885a00 <sys_common::gnu::libbacktrace::print::pcinfo_cb::h29c7688dfe185d9fyht>, 
    error_callback=0x7f36a58859f0 <sys_common::gnu::libbacktrace::print::error_cb::h9d640c5e5585541eJgt>, data=0x7f369d7ed170)
    at /var/tmp/portage/dev-lang/rust-9999/work/rust-9999/src/libbacktrace/fileline.c:176
#2  0x00007f36a588610c in sys::backtrace::tracing::imp::write::trace_fn::h3227ea145b706b5bSst ()
   from /usr/lib64/rust-9999/libstd-gentoo-git.so
#3  0x00007f369f8b75c9 in _Unwind_Backtrace (
    trace=0x7f36a5885cb0 <sys::backtrace::tracing::imp::write::trace_fn::h3227ea145b706b5bSst>, trace_argument=0x7f369d7ed518)
    at /var/tmp/portage/sys-devel/gcc-5.2.0/work/gcc-5.2.0/libgcc/unwind.inc:295
#4  0x00007f36a5885b5a in sys::backtrace::tracing::imp::write::h82b779db8318b1850qt () from /usr/lib64/rust-9999/libstd-gentoo-git.so
#5  0x00007f36a5883287 in panicking::on_panic::h5d10db3f19f75694zqx () from /usr/lib64/rust-9999/libstd-gentoo-git.so
#6  0x00007f36a584fbdf in sys_common::unwind::begin_unwind_inner::h021af668201d101f3es ()
   from /usr/lib64/rust-9999/libstd-gentoo-git.so
#7  0x00007f36a5850619 in sys_common::unwind::begin_unwind_fmt::h6ae185d70e9749249ds ()
   from /usr/lib64/rust-9999/libstd-gentoo-git.so
#8  0x00007f36a34ae205 in front::map::Map$LT$$u27$ast$GT$::get_path_elem::hcac69fe7ff0a5591Sfb ()
   from /usr/lib64/rust-9999/librustc-gentoo-git.so
#9  0x00007f36a3768af8 in front::map::Map$LT$$u27$ast$GT$::with_path_next::h7677687426421862442 ()
   from /usr/lib64/rust-9999/librustc-gentoo-git.so
#10 0x00007f36a36070ea in middle::ty::ctxt$LT$$u27$tcx$GT$::item_path_str::h093d7dc118b8ded1nUf ()
   from /usr/lib64/rust-9999/librustc-gentoo-git.so
#11 0x00007f36a3605edc in middle::def_id::DefId.fmt..Debug::fmt::h084461e0056999ebtRo ()
   from /usr/lib64/rust-9999/librustc-gentoo-git.so
#12 0x00007f36a58eb226 in fmt::write::h4db63ca58df27bafp0W () from /usr/lib64/rust-9999/libstd-gentoo-git.so
#13 0x00007f36a58c3e31 in fmt::builders::DebugTuple$LT$$u27$a$C$$u20$$u27$b$GT$::field::h434f658db5f3c7ecRnW ()
   from /usr/lib64/rust-9999/libstd-gentoo-git.so
#14 0x00007f36a35961b0 in middle::def::Def...std..fmt..Debug::fmt::h95a2b86eebd51a73Fon ()
   from /usr/lib64/rust-9999/librustc-gentoo-git.so
#15 0x00007f36a58eb226 in fmt::write::h4db63ca58df27bafp0W () from /usr/lib64/rust-9999/libstd-gentoo-git.so
#16 0x00007f36a58c3905 in fmt::builders::DebugStruct$LT$$u27$a$C$$u20$$u27$b$GT$::field::he7df159292fb73ecXiW ()
   from /usr/lib64/rust-9999/libstd-gentoo-git.so
#17 0x00007f36a3606e12 in fmt::_$RF$$u27$a$u20$T.Debug::fmt::h9876525571199719911 () from /usr/lib64/rust-9999/librustc-gentoo-git.so
#18 0x00007f36a58eb226 in fmt::write::h4db63ca58df27bafp0W () from /usr/lib64/rust-9999/libstd-gentoo-git.so
#19 0x00007f36a58505bb in sys_common::unwind::begin_unwind_fmt::h6ae185d70e9749249ds ()
   from /usr/lib64/rust-9999/libstd-gentoo-git.so
#20 0x00007f36a35a82b1 in middle::const_eval::eval_const_expr_partial::h77eb81c891e44397Nyk ()
   from /usr/lib64/rust-9999/librustc-gentoo-git.so
#21 0x00007f36a443099d in astconv::ast_ty_to_ty::h446730aafa9ba3b32ox () from /usr/lib64/rust-9999/librustc_typeck-gentoo-git.so
#22 0x00007f36a449c199 in collect::convert_field::h079a992ee3267235d5y () from /usr/lib64/rust-9999/librustc_typeck-gentoo-git.so
#23 0x00007f36a4488ab0 in collect::convert_item::h6dd288f7ad9918efTdz () from /usr/lib64/rust-9999/librustc_typeck-gentoo-git.so
#24 0x00007f36a4483a88 in collect::collect_item_types::hdc4b9b528a28e1a1ppy ()
   from /usr/lib64/rust-9999/librustc_typeck-gentoo-git.so
#25 0x00007f36a44d1b9c in check_crate::hc33dccfaaa753e70ZGE () from /usr/lib64/rust-9999/librustc_typeck-gentoo-git.so
#26 0x00007f36a5da2acf in driver::phase_3_run_analysis_passes::closure.21555 ()
   from /usr/lib64/rust-9999/librustc_driver-gentoo-git.so
#27 0x00007f36a5d851ed in middle::ty::context::ctxt$LT$$u27$tcx$GT$::create_and_enter::h14912410508915335040 ()
   from /usr/lib64/rust-9999/librustc_driver-gentoo-git.so
#28 0x00007f36a5d809a2 in driver::phase_3_run_analysis_passes::h6812549652698182288 ()
   from /usr/lib64/rust-9999/librustc_driver-gentoo-git.so
#29 0x00007f36a5d612f4 in driver::compile_input::h14af076c634191100ba () from /usr/lib64/rust-9999/librustc_driver-gentoo-git.so
#30 0x00007f36a5ec6d3c in run_compiler::h89a832461de3e8ab3qc () from /usr/lib64/rust-9999/librustc_driver-gentoo-git.so
#31 0x00007f36a5ec45a7 in boxed::F.FnBox$LT$A$GT$::call_box::h4415565791460127255 ()
   from /usr/lib64/rust-9999/librustc_driver-gentoo-git.so
#32 0x00007f36a5ec3eb5 in sys_common::unwind::try::try_fn::h17089024600160099748 ()
   from /usr/lib64/rust-9999/librustc_driver-gentoo-git.so
#33 0x00007f36a5882b89 in __rust_try () from /usr/lib64/rust-9999/libstd-gentoo-git.so
#34 0x00007f36a58773cf in sys_common::unwind::try::inner_try::h9d46b930d0260ed7Dbs () from /usr/lib64/rust-9999/libstd-gentoo-git.so
#35 0x00007f36a5ec404f in boxed::F.FnBox$LT$A$GT$::call_box::h8089523330245650700 ()
   from /usr/lib64/rust-9999/librustc_driver-gentoo-git.so
#36 0x00007f36a588ae34 in sys::thread::Thread::new::thread_start::h0a7752ba7c557a49oJw ()
   from /usr/lib64/rust-9999/libstd-gentoo-git.so
#37 0x00007f369fdc2484 in start_thread (arg=0x7f369d7ff700) at pthread_create.c:334
#38 0x00007f36a55145cd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

[steveklabnik]

It looks like this no longer ICEs rust-lang/glacier#85