ICE: assertion failed: leak_check(infcx, &skol_map, snapshot).is_ok()

[bytwise]

Code:

trait Wrap<'b> {
    fn foo(&'b mut self);
}

struct Wrapper<P>(P);

impl<'b, P> Wrap<'b> for Wrapper<P>
where P: Process<'b>,
      <P as Process<'b>>::Item: Iterator {
    fn foo(&mut self) {}
}


pub trait Process<'a> {
    type Item;
    fn bar(&'a self);
}

fn push_process<P>(process: P) where P: Process<'static> {
    let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
}

fn main() {}

Output:

error: internal compiler error: unexpected panic
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 'assertion failed: leak_check(infcx, &skol_map, snapshot).is_ok()', /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/librustc/middle/infer/higher_ranked/mod.rs:561

stack backtrace:
   1:        0x10a98b4b5 - sys::backtrace::write::h64ca2fb259c4ae97lCt
   2:        0x10a9ad94f - failure::on_fail::h64ff5ae6887860cc0Hz
   3:        0x10a9195ca - rt::unwind::begin_unwind_inner::h1d4bc098fd350446Qpz
   4:        0x107a5b05c - rt::unwind::begin_unwind::h14752733970416986751
   5:        0x107de5abb - middle::traits::select::SelectionContext<'cx, 'tcx>::vtable_impl::hddc0cc735340ecc8snT
   6:        0x107df3983 - middle::infer::InferCtxt<'a, 'tcx>::try::h7243598630119042649
   7:        0x107de02d7 - middle::traits::select::SelectionContext<'cx, 'tcx>::confirm_candidate::hac288b7baea2474883S
   8:        0x107dc1b0d - middle::traits::select::SelectionContext<'cx, 'tcx>::select::h40303230723bb5b2GmR
   9:        0x107dbf4a1 - middle::traits::fulfill::FulfillmentContext<'tcx>::select::hd311ca92298c935c5uP
  10:        0x107dbe95f - middle::traits::fulfill::FulfillmentContext<'tcx>::select_where_possible::h0ddf391ab631b9dcbuP
  11:        0x107706075 - check::vtable::select_fcx_obligations_where_possible::hadc6eeee207ed13f6lb
  12:        0x107705812 - check::vtable::select_all_fcx_obligations_or_error::h185f88f1cc7da26fdkb
  13:        0x107789b8a - check::check_bare_fn::h92d153344310f88bH3j
  14:        0x1077816f5 - check::check_item::hffd8f154a5736127umk
  15:        0x10784906f - check_crate::unboxed_closure.30671
  16:        0x107844873 - check_crate::h32fc7f8788be683523x
  17:        0x1071b4982 - driver::phase_3_run_analysis_passes::h4c5cf0d8fe5d55degwa
  18:        0x10719b420 - driver::compile_input::h31580cbd7ea87613xba
  19:        0x107266fda - monitor::unboxed_closure.22557
  20:        0x107265735 - thunk::F.Invoke<A, R>::invoke::h6367419564961841226
  21:        0x107264510 - rt::unwind::try::try_fn::h7763956589852599824
  22:        0x10aa142a9 - rust_try_inner
  23:        0x10aa14296 - rust_try
  24:        0x107264c0c - thunk::F.Invoke<A, R>::invoke::h16724184168577887652
  25:        0x10a99b154 - sys::thread::thread_start::hbd8f2f8bdd3a3baadrw
  26:     0x7fff877a32fc - _pthread_body
  27:     0x7fff877a3279 - _pthread_body

Rust version:

rustc 1.0.0-nightly (b47aebe3f 2015-02-26) (built 2015-02-26)
binary: rustc
commit-hash: b47aebe3fc2da06c760fd8ea19f84cbc41d34831
commit-date: 2015-02-26
build-date: 2015-02-26
host: x86_64-apple-darwin
release: 1.0.0-nightly

[pmarcelll]

I can't reproduce it on rustc 1.2.0-nightly (0250ff9a5 2015-06-17).

[apasel422]

With rustc 1.3.0-nightly (e4e93196e 2015-07-14), this yields:

foo.rs:20:36: 20:62 error: the trait `for<'b> Process<'b>` is not implemented for the type `P` [E0277]
foo.rs:20     let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.rs:20:36: 20:62 help: run `rustc --explain E0277` to see a detailed explanation
foo.rs:20:36: 20:62 error: the trait `for<'b> core::iter::Iterator` is not implemented for the type `<P as Process<'b>>::Item` [E0277]
foo.rs:20     let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.rs:20:36: 20:62 help: run `rustc --explain E0277` to see a detailed explanation
foo.rs:20:36: 20:62 note: `<P as Process<'b>>::Item` is not an iterator; maybe try calling `.iter()` or a similar method
foo.rs:20     let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.rs:20:36: 20:62 error: cannot infer an appropriate lifetime for lifetime parameter `'b` due to conflicting requirements
foo.rs:20     let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~
note: first, the lifetime cannot outlive lifetime ReSkolemized(0, BrNamed(DefId { krate: 0, node: 64 }, "\'b"(61)))...
foo.rs:20:36: 20:62 note: ...so that trait type parameters matches those specified on the impl (expected `Wrap<'b>`, found `Wrap<'_>`)
foo.rs:20     let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~
note: but, the lifetime must be valid for the static lifetime...
foo.rs:20:36: 20:62 note: ...so that trait type parameters matches those specified on the impl (expected `Process<'_>`, found `Process<'static>`)
foo.rs:20     let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~
error: aborting due to 3 previous errors

[ebfull]

This isn't fixed yet. The tests that were added only pass because debug assertions are disabled when @bors tests stuff.

[apasel422]

@ebfull Can you elaborate on this? Does this still cause an ICE?

On Saturday, September 12, 2015, Eduard Burtescu [email protected]
wrote:

Reopened #22872 #22872.

—
Reply to this email directly or view it on GitHub
#22872 (comment).

[eddyb]

@apasel422 Yes, it always had, just that debug assertions became opt-in.

[apasel422]

Is there an issue open to get bors to run with debug assertions enabled,
then? Seems dangerous not to.

On Saturday, September 12, 2015, Eduard Burtescu [email protected]
wrote:

@apasel422 https://github.com/apasel422 Yes, it always had, just that
debug assertions became opt-in.

—
Reply to this email directly or view it on GitHub
#22872 (comment).

[nikomatsakis]

Yes, we need to have bors checking with debug-assertions! (Or else we should just never use them in rustc, perhaps.)

[arielb1]

@nikomatsakis

seems like the debug assertion is wrong because of #21974

[arielb1]

maybe match_poly_trait_refs can detect this however. Actually, that can't work, given that we select cache_fresh_trait_pred=Binder(TraitPredicate(<P as Process<'static>>)), candidate=Ok(Some(ParamCandidate(Binder (<P as Process<'static>>))))

[pnkfelix]

Yes, we need to have bors checking with debug-assertions! (Or else we should just never use them in rustc, perhaps.)

having such a build configuration is related to #17166 and #27010

[Stebalien]

Based on the comments here, this should probably not be labeled E-needstest.

[Mark-Simulacrum]

Today, this produces the following, which is presumably correct? Either way, marking as E-needstest.

error[E0277]: the trait bound `for<'b> P: Process<'b>` is not satisfied
  --> test.rs:20:36
   |
20 |     let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
   |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'b> Process<'b>` is not implemented for `P`
   |
   = help: consider adding a `where for<'b> P: Process<'b>` bound
   = note: required because of the requirements on the impl of `for<'b> Wrap<'b>` for `Wrapper<P>`
   = note: required for the cast to the object type `for<'b> Wrap<'b>`

error[E0277]: the trait bound `for<'b> <P as Process<'b>>::Item: std::iter::Iterator` is not satisfied
  --> test.rs:20:36
   |
20 |     let _: Box<for<'b> Wrap<'b>> = Box::new(Wrapper(process));
   |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'b> std::iter::Iterator` is not implemented for `<P as Process<'b>>::Item`
   |
   = note: `<P as Process<'b>>::Item` is not an iterator; maybe try calling `.iter()` or a similar method
   = note: required because of the requirements on the impl of `for<'b> Wrap<'b>` for `Wrapper<P>`
   = note: required for the cast to the object type `for<'b> Wrap<'b>`

error: aborting due to 2 previous errors

[eddyb]

@Mark-Simulacrum Is that with debug assertions enabled?

[Mark-Simulacrum]

I think so. The way I check is with RUST_LOG=debug, which outputs debug logging... this is also on a rustc compiled locally with debug-assertions = true in the config.toml.