ICE in `libsyntax/diagnostic.rs`

[swizard0]

% uname -a 
Darwin pair 14.1.0 Darwin Kernel Version 14.1.0: Mon Dec 22 23:10:38 PST 2014; root:xnu-2782.10.72~2/RELEASE_X86_64 x86_64

% rustc --version --verbose
rustc 1.0.0-dev (a45e11773 2015-01-28 11:01:36 +0000)
binary: rustc
commit-hash: a45e117733b866302fa99390553d1c548508dcca
commit-date: 2015-01-28 11:01:36 +0000
host: x86_64-apple-darwin
release: 1.0.0-dev

% RUST_BACKTRACE=1 rustc --cfg=test rs_ffi_utils.rs
rs_ffi_utils.rs:236:1: 248:2 error: internal compiler error: coherence failed to report ambiguity: cannot locate the impl of the trait `MemWrite` for the type `Seq<&'o T>`
rs_ffi_utils.rs:236 impl<'o, T> MemWrite for Seq<&'o T> where T: Blob, &'o T: MemWrite {
rs_ffi_utils.rs:237     fn write_to_mem<'a>(&self, dst: &'a mut [u8]) -> Result<&'a [u8], MemAreaError> {
rs_ffi_utils.rs:238         Ok(dst)
rs_ffi_utils.rs:239     }
rs_ffi_utils.rs:240
rs_ffi_utils.rs:241     fn size_required(&self) -> usize {
                    ...
note: the compiler unexpectedly panicked. 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
thread 'rustc' panicked at 'Box<Any>', /Users/swizard/distr/rust/src/libsyntax/diagnostic.rs:130

stack backtrace:
   1:        0x10dda37a7 - sys::backtrace::write::ha7c2a314980a2c9fvbu
   2:        0x10ddc9c5c - failure::on_fail::h6e454f5b61899a9aqbB
   3:        0x10dd2b068 - rt::unwind::begin_unwind_inner::h197e2c88eee2bed0mTA
   4:        0x10d4b2897 - rt::unwind::begin_unwind::h2026034157403174692
   5:        0x10d4b282c - diagnostic::SpanHandler::span_bug::hd1799d165b9b1455PGE
   6:        0x10aff6d1a - middle::traits::error_reporting::report_fulfillment_errors::hea46febf461f61d7YHN
   7:        0x10a95ed38 - check::vtable::select_all_fcx_obligations_or_error::h76d8a7711ec3b289Upb
   8:        0x10a9da0ae - check::wf::CheckTypeWellFormedVisitor<'ccx, 'tcx>::check_item_well_formed::h1acd04dfde9bfc73a7i
   9:        0x10aac784e - check_crate::closure.32081
  10:        0x10aac2e0f - check_crate::haecc3fe6465ec7b6ZNy
  11:        0x10a48c8eb - driver::phase_3_run_analysis_passes::h79664d81b6b5b4e4NFa
  12:        0x10a472e5c - driver::compile_input::hec1fc484fb82a3b3Bba
  13:        0x10a53b50e - run_compiler::hc5f9e0285db79a55n9b
  14:        0x10a53862f - thunk::F.Invoke<A, R>::invoke::h4736678281155978274
  15:        0x10a5372c0 - rt::unwind::try::try_fn::h3346791736825056138
  16:        0x10de42a09 - rust_try_inner
  17:        0x10de429f6 - rust_try
  18:        0x10a537984 - thunk::F.Invoke<A, R>::invoke::h14937575134341006880
  19:        0x10ddb4313 - sys::thread::thread_start::hd065b218eff37dc2J3w
  20:     0x7fff87bec268 - _pthread_body
  21:     0x7fff87bec1e5 - _pthread_body

[jdm]

#21942 reports that the nalgebra library hits this.

[ebfull]

image library seems to hit this too:

/root/.cargo/git/checkouts/image-f4d4ca6613133df7/master/src/imageops/colorops.rs:62:46: 62:66 error: internal compiler error: coherence failed to report ambiguity: cannot locate the impl of the trait `traits::Num` for the type `<<I as image::GenericImage>::Pixel as buffer::Pixel>::Subpixel`
/root/.cargo/git/checkouts/image-f4d4ca6613133df7/master/src/imageops/colorops.rs:62     let max: <I::Pixel as Pixel>::Subpixel = Primitive::max_value();
                                                                                                                                  ^~~~~~~~~~~~~~~~~~~~
note: the compiler unexpectedly panicked. 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
thread 'rustc' panicked at 'Box<Any>', /rustc-nightly/src/libsyntax/diagnostic.rs:129

stack backtrace:
   1:     0x7f53cd4f14b0 - sys::backtrace::write::h7f470cc4f24154a6ZTA
   2:     0x7f53cd516140 - failure::on_fail::h61642dd3c2c5b7f9JFJ
   3:     0x7f53cd46e0b0 - rt::unwind::begin_unwind_inner::hd970c8feb3e9463d4jJ
   4:     0x7f53ca812410 - rt::unwind::begin_unwind::h3673386443430583256
   5:     0x7f53ca8123a0 - diagnostic::SpanHandler::span_bug::h5ed17cc567e332df74E
   6:     0x7f53cb585c60 - middle::traits::error_reporting::report_fulfillment_errors::hc272c1e020beb1a9suO
   7:     0x7f53ccbb7ad0 - check::vtable::select_all_fcx_obligations_or_error::h34bbe66b3fb3edf0oPb
   8:     0x7f53ccc64410 - check::check_bare_fn::h727526b64e64c055Scn
   9:     0x7f53ccc5bb10 - check::check_item::h2ba91f101eebedf8lwn
  10:     0x7f53ccc62100 - visit::walk_item::h7118923990314441683
  11:     0x7f53ccc62100 - visit::walk_item::h7118923990314441683
  12:     0x7f53ccd2f480 - check_crate::closure.35395
  13:     0x7f53ccd29d50 - check_crate::hd29eb55a52d61a01OxB
  14:     0x7f53cdb1ec80 - driver::phase_3_run_analysis_passes::h6d35bf1217485c05SGa
  15:     0x7f53cdb04d60 - driver::compile_input::h782a70ecc086dc68Eba
  16:     0x7f53cdbd5f30 - run_compiler::had38ec949ad218b25bc
  17:     0x7f53cdbd4590 - thunk::F.Invoke<A, R>::invoke::h12150908996860458254
  18:     0x7f53cdbd3480 - rt::unwind::try::try_fn::h16942177747375777417
  19:     0x7f53cd58b980 - rust_try_inner
  20:     0x7f53cd58b970 - rust_try
  21:     0x7f53cdbd3730 - thunk::F.Invoke<A, R>::invoke::h6840892055334168534
  22:     0x7f53cd501db0 - sys::thread::thread_start::h4240f311c9074a7baOE
  23:     0x7f53c764ffe0 - start_thread
  24:     0x7f53cd0ecc99 - __clone
  25:                0x0 - <unknown>

i'm running on a more recent rust version as well:

rustc 1.0.0-dev (39b463f15 2015-02-12 20:03:50 +0000)
binary: rustc
commit-hash: 39b463f15328f448c13fa990f9fc8897e0af55c2
commit-date: 2015-02-12 20:03:50 +0000
host: x86_64-unknown-linux-gnu
release: 1.0.0-dev

[nwin]

This must have been introduced recently rustc 1.0.0-nightly (3ef8ff1 2015-02-12 00:38:24 +0000) works…

[tomaka]

The issue has been reported 16 days ago, so it wasn't introduced recently. However image started hitting this with the 2015-02-13 nightly.

[AnthIste]

Trying to run this snippet in the rust playpen gives an ICE:

trait MyTrait {
    fn do_something(&self);
}

impl<'a> MyTrait for MyTrait + 'a {
    fn do_something(&self) {
        println!("MyTrait");
    }
}

fn main() {
}

The error log is:

<anon>:5:1: 9:2 error: internal compiler error: coherence failed to report ambiguity: cannot locate the impl of the trait `MyTrait` for the type `MyTrait + 'a`
<anon>:5 impl<'a> MyTrait for MyTrait + 'a {
<anon>:6     fn do_something(&self) {
<anon>:7         println!("MyTrait");
<anon>:8     }
<anon>:9 }
note: the compiler unexpectedly panicked. 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
thread 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:129

[fenhl]

router will hit this too, as soon as iron/router#74 is merged.

[andrew-d]

I took a quick look at this and it's beyond my knowledge to fix, but the bug is being triggered here, and it looks like maybe @nikomatsakis or @flaper87 was the last one to touch that code?

[nikomatsakis]

Hmm so the minimized code snippet here:

trait MyTrait {
    fn do_something(&self);
}

impl<'a> MyTrait for MyTrait + 'a {
    fn do_something(&self) {
        println!("MyTrait");
    }
}

fn main() {
}

is actually just broken code. That is, the compiler automatically generates an impl of MyTrait for MyTrait, so you shouldn't need to write one -- but we should give a better error, of course.

[nikomatsakis]

I have a fix for some of these problems which I'm going to post, but I suspect there are different issues arising, so I'm not going to declare this bug fixed until I've been able to investigate more of the crates in question.