ICE with cross-crate projection

[ziish]

Running rustdoc all testcases for this crate fails with an ICE. The relevant testcase is currently disabled. To enable it go to image/impl_core.rs:24 and remove the ignore marker.

rustc --version --verbose:

rustc 1.14.0-nightly (16eeeac78 2016-10-18)
binary: rustc
commit-hash: 16eeeac783d2ede28e09f2a433c612dea309fe33
commit-date: 2016-10-18
host: x86_64-pc-windows-msvc
release: 1.14.0-nightly
LLVM version: 3.9

This is the result of cargo test:

    Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
     Running target\debug\deps\img-7ec732e017a2f5eb.exe

running 4 tests
test px::test_arithmetic ... ok
test px::test_raw_buffer_funcs ... ok
test scalar::test_arithmetic ... ok
test image::test_image_buffer ... ok

test result: ok. 4 passed; 0 failed; 0 ignored; 0 measured

   Doc-tests img

running 8 tests
test px::generic::PixelArithmetic_0 ... ok
test image::generics::Image_0 ... ok
test image::impl_core::ImageVal_0 ... FAILED
test px::generic::Pixel::calc_minimum_pitch_0 ... ok
test px::generic::Pixel_0 ... ok
test scalar::generic::Scalar_0 ... ok
test px::impl_core::PixelVal_0 ... ok
test scalar::impl_core::ScalarVal_0 ... ok

failures:

---- image::impl_core::ImageVal_0 stdout ----
        error: internal compiler error: ../src/librustc\traits\specialize/mod.rs:198: specializes: obligation `Obligation(predicate=Binder(ProjectionPredicate(ProjectionTy { trait_
ref: <_ as img::PixelArithmetic>, item_name: ScalarT(4511) }, _)),depth=1)` has inference types/regions

thread 'image::impl_core::ImageVal_0' panicked at 'Box<Any>', ../src/librustc_errors/lib.rs:656
stack backtrace:
   0:      0x7fee2c7f804 - <u32 as std::sys::IsZero>::is_zero::hb501b477ff597565
   1:      0x7fee2c7bca9 - std::panicking::Location::line::h756ee230b7a7fab3
   2:      0x7fee2c7c6ed - std::panicking::rust_panic_with_hook::hcd9d05f53fa0dafc
   3:      0x7fef3d128ea - <unknown>
   4:      0x7fef3d2608d - rustc_errors::Handler::bug::haca77c19c882b432
   5:      0x7fee197b2d5 - <rustc::util::ppaux::TraitAndProjections<'tcx> as core::fmt::Debug>::fmt::hb5d03a0e1370418a
   6:      0x7fee189b262 - rustc::session::bug_fmt::hde22f071bf5a80ea
   7:      0x7fee189af7c - rustc::session::bug_fmt::hde22f071bf5a80ea
   8:      0x7fee1975d31 - <rustc::util::ppaux::TraitAndProjections<'tcx> as core::fmt::Debug>::fmt::hb5d03a0e1370418a
   9:      0x7fee16c6dd7 - <unknown>
  10:      0x7fee19165d5 - rustc::ty::context::TyCtxt::free_region_map::h82e8c7df0d75ed07
  11:      0x7fee18d5cc6 - rustc::traits::specialize::specializes::hc06f881417f11f03
  12:      0x7fee18c8ae0 - rustc::traits::select::SelectionContext::evaluate_obligation_conservatively::h7dc149b5b7563089
  13:      0x7fee18c29da - rustc::traits::select::SelectionContext::evaluate_obligation_conservatively::h7dc149b5b7563089
  14:      0x7fee18c0da7 - rustc::traits::select::SelectionContext::evaluate_obligation_conservatively::h7dc149b5b7563089
  15:      0x7fee18c0430 - rustc::traits::select::SelectionContext::evaluate_obligation_conservatively::h7dc149b5b7563089
  16:      0x7fee18bfc9a - rustc::traits::select::SelectionContext::evaluate_obligation::h918f689b79ed78ea
  17:      0x7fee1da81e4 - rustc_typeck::check::method::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::lookup_method_in_trait_adjusted::h23bf843644a86a1c
  18:      0x7fee1dce0d8 - rustc_typeck::check::op::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::check_user_unop::hccfdc1643ed36810
  19:      0x7fee1dccd9c - rustc_typeck::check::op::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::check_binop::h5fef06b12193950d
  20:      0x7fee1dcc782 - rustc_typeck::check::op::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::check_binop::h5fef06b12193950d
  21:      0x7fee1dfa4ca - rustc_typeck::check::FnCtxt::check_struct_path::h0a3b8cb3a9a77f78
  22:      0x7fee1dfa066 - rustc_typeck::check::FnCtxt::check_struct_path::h0a3b8cb3a9a77f78
  23:      0x7fee1dfadf1 - rustc_typeck::check::FnCtxt::check_struct_path::h0a3b8cb3a9a77f78
  24:      0x7fee1dfa066 - rustc_typeck::check::FnCtxt::check_struct_path::h0a3b8cb3a9a77f78
  25:      0x7fee1e0accb - rustc_typeck::check::FnCtxt::check_stmt::he33c1a72110694ef
  26:      0x7fee1e0b1ca - rustc_typeck::check::FnCtxt::check_block_no_value::h45608011ee74f15e
  27:      0x7fee1dd5806 - <rustc_typeck::check::GatherLocalsVisitor<'a, 'gcx, 'tcx> as rustc::hir::intravisit::Visitor<'gcx>>::visit_ty::hd4c15b543ae85d6e
  28:      0x7fee1dd38b0 - rustc_typeck::check::check_drop_impls::hf0fd3120466d7e2f
  29:      0x7fee1dd7f79 - rustc_typeck::check::check_item_body::h3223fb19b212e96a
  30:      0x7fee1dd072b - rustc_typeck::check::check_item_bodies::ha98a70a8fce7849f
  31:      0x7fee1e4f563 - rustc_typeck::check_crate::hd5386d41de8aa25b
  32:      0x7fee205b815 - <rustc_driver::Compilation as core::fmt::Debug>::fmt::hfc4845a68da21d3e
  33:      0x7fee1f8a06e - <unknown>
  34:      0x7fee2012353 - rustc_driver::driver::compile_input::h5b63ccd49eeeb98b
  35:      0x7fee2144800 - <unknown>
  36:      0x7fee2c81ce1 - _rust_maybe_catch_panic
  37:      0x7fee227755e - rustdoc::test::run::hcc44ccd17e8a0827
  38:      0x7fee2145a4f - <unknown>
  39:      0x7fee2c81ce1 - _rust_maybe_catch_panic
  40:      0x7fee5e63b4b - <unknown>
  41:      0x7fee2c81ce1 - _rust_maybe_catch_panic
  42:      0x7fee5e6b7fa - <unknown>
  43:      0x7fee2c79b2e - std::sys::thread::Thread::new::hf599b376c47e7cb9
  44:         0x76df59cc - BaseThreadInitThunk
thread 'image::impl_core::ImageVal_0' panicked at 'couldn't compile the test', ../src/librustdoc\test.rs:283
stack backtrace:
   0:      0x7fee2c7f804 - <u32 as std::sys::IsZero>::is_zero::hb501b477ff597565
   1:      0x7fee2c7bca9 - std::panicking::Location::line::h756ee230b7a7fab3
   2:      0x7fee2c7c6ed - std::panicking::rust_panic_with_hook::hcd9d05f53fa0dafc
   3:      0x7fee2142cd3 - <unknown>
   4:      0x7fee2278e14 - rustdoc::test::run::hcc44ccd17e8a0827
   5:      0x7fee2145a4f - <unknown>
   6:      0x7fee2c81ce1 - _rust_maybe_catch_panic
   7:      0x7fee5e63b4b - <unknown>
   8:      0x7fee2c81ce1 - _rust_maybe_catch_panic
   9:      0x7fee5e6b7fa - <unknown>
  10:      0x7fee2c79b2e - std::sys::thread::Thread::new::hf599b376c47e7cb9
  11:         0x76df59cc - BaseThreadInitThunk


failures:
    image::impl_core::ImageVal_0

test result: FAILED. 7 passed; 1 failed; 0 ignored; 0 measured

error: test failed

This fails on stable and nightly. I do not have time to create a reduced test case right now. Hope this helps anyway.

[TimNN]

Regression from 1.9.0 to 1.10.0.

Requires the ice'ing code to be in a separate crate.

[TimNN]

This was introduced between nightly-2016-05-10 and nightly-2016-05-12 (Changes). I suspect this was an effect of #33425.

I reduced the code some, although it can probably be reduced further, see https://gist.github.com/7cd880ff5d32b7de65c7910935d36d6e.

[brson]

Thanks @TimNN !

[brson]

Reduced test cases wanted!

Nominating to get eyes on my compiler team.

[eddyb]

@rust-lang/compiler Does this look like any known lifetime-related bug that you can think of?

[nikomatsakis]

Nothing that jumps to mind. I can try to dig in a bit.

[ziish]

Thanks for the effort so far!

I think this test case is easier to analyze: https://gist.github.com/physhh/0d4046b38940a309ce2b6e0ce516c4a9

Everytime I tried to further reduce the amount of types involved the ICE disappeared.

[TimNN]

@physhh: Nice work!

I just remembered something I noticed while reducing the initial code:

Commenting out either one of the Mul impl's makes the ICE go away - irrespective of whether it is the one that applies in main.rs or not.

[nikomatsakis]

Sorry for being slow to act on this. I am able to reproduce the problem. Investigating.