Rustc panicked at Box<Any>: impossible case reached

[editicalu]

Rustc panicked at documenting a dependent crate in my project.

Meta

rustc --version --verbose
rustc 1.30.0-nightly (6e0f1cc15 2018-09-05)
binary: rustc
commit-hash: 6e0f1cc1587676b58cfff06bf3a10ea7fba7086e
commit-date: 2018-09-05
host: x86_64-unknown-linux-gnu
release: 1.30.0-nightly
LLVM version: 8.0

$ RUST_BACKTRACE=1 cargo doc --jobs=1 
 Documenting typenum v1.10.0                                                    
error: internal compiler error: librustc/traits/structural_impls.rs:178: impossible case reached

thread '<unnamed>' panicked at 'Box<Any>', librustc_errors/lib.rs:587:9
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:71
             at libstd/sys_common/backtrace.rs:59
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:211
   3: std::panicking::default_hook
             at libstd/panicking.rs:227
   4: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:477
   5: std::panicking::begin_panic
   6: rustc_errors::Handler::bug
   7: rustc::util::bug::opt_span_bug_fmt::{{closure}}
   8: rustc::ty::context::tls::with_opt::{{closure}}
   9: rustc::ty::context::tls::with_context_opt
  10: rustc::ty::context::tls::with_opt
  11: rustc::util::bug::opt_span_bug_fmt
  12: rustc::util::bug::bug_fmt
  13: rustc::traits::structural_impls::<impl rustc::ty::context::Lift<'tcx> for rustc::traits::SelectionError<'a>>::lift_to_tcx
  14: rustc::ty::context::TyCtxt::lift_to_global
  15: rustc::traits::select::SelectionContext::candidate_from_obligation
  16: rustc::traits::select::SelectionContext::evaluate_stack
  17: rustc::dep_graph::graph::DepGraph::with_anon_task
  18: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  19: rustc::infer::InferCtxt::probe
  20: <&'a mut I as core::iter::iterator::Iterator>::next
  21: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  22: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  23: rustc::dep_graph::graph::DepGraph::with_anon_task
  24: rustc::traits::select::SelectionContext::candidate_from_obligation
  25: rustc::traits::select::SelectionContext::evaluate_stack
  26: rustc::dep_graph::graph::DepGraph::with_anon_task
  27: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  28: rustc::infer::InferCtxt::probe
  29: <&'a mut I as core::iter::iterator::Iterator>::next
  30: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  31: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  32: rustc::dep_graph::graph::DepGraph::with_anon_task
  33: rustc::traits::select::SelectionContext::candidate_from_obligation
  34: rustc::traits::select::SelectionContext::evaluate_stack
  35: rustc::dep_graph::graph::DepGraph::with_anon_task
  36: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  37: rustc::infer::InferCtxt::probe
  38: <&'a mut I as core::iter::iterator::Iterator>::next
  39: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  40: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  41: rustc::dep_graph::graph::DepGraph::with_anon_task
  42: rustc::traits::select::SelectionContext::candidate_from_obligation
  43: rustc::traits::select::SelectionContext::evaluate_stack
  44: rustc::dep_graph::graph::DepGraph::with_anon_task
  45: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  46: rustc::infer::InferCtxt::probe
  47: <&'a mut I as core::iter::iterator::Iterator>::next
  48: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  49: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  50: rustc::dep_graph::graph::DepGraph::with_anon_task
  51: rustc::traits::select::SelectionContext::candidate_from_obligation
  52: rustc::traits::select::SelectionContext::evaluate_stack
  53: rustc::dep_graph::graph::DepGraph::with_anon_task
  54: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  55: rustc::infer::InferCtxt::probe
  56: <&'a mut I as core::iter::iterator::Iterator>::next
  57: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  58: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  59: rustc::dep_graph::graph::DepGraph::with_anon_task
  60: rustc::traits::select::SelectionContext::candidate_from_obligation
  61: rustc::traits::select::SelectionContext::evaluate_stack
  62: rustc::dep_graph::graph::DepGraph::with_anon_task
  63: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  64: rustc::infer::InferCtxt::probe
  65: <&'a mut I as core::iter::iterator::Iterator>::next
  66: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  67: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  68: rustc::dep_graph::graph::DepGraph::with_anon_task
  69: rustc::traits::select::SelectionContext::candidate_from_obligation
  70: rustc::traits::select::SelectionContext::evaluate_stack
  71: rustc::dep_graph::graph::DepGraph::with_anon_task
  72: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  73: rustc::infer::InferCtxt::probe
  74: <&'a mut I as core::iter::iterator::Iterator>::next
  75: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  76: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  77: rustc::dep_graph::graph::DepGraph::with_anon_task
  78: rustc::traits::select::SelectionContext::candidate_from_obligation
  79: rustc::traits::select::SelectionContext::evaluate_stack
  80: rustc::dep_graph::graph::DepGraph::with_anon_task
  81: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  82: rustc::infer::InferCtxt::probe
  83: <&'a mut I as core::iter::iterator::Iterator>::next
  84: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  85: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  86: rustc::dep_graph::graph::DepGraph::with_anon_task
  87: rustc::traits::select::SelectionContext::candidate_from_obligation
  88: rustc::traits::select::SelectionContext::evaluate_stack
  89: rustc::dep_graph::graph::DepGraph::with_anon_task
  90: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  91: rustc::infer::InferCtxt::probe
  92: <&'a mut I as core::iter::iterator::Iterator>::next
  93: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  94: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  95: rustc::dep_graph::graph::DepGraph::with_anon_task
  96: rustc::traits::select::SelectionContext::candidate_from_obligation
  97: rustc::traits::select::SelectionContext::evaluate_stack
  98: rustc::dep_graph::graph::DepGraph::with_anon_task
  99: rustc::traits::select::SelectionContext::evaluate_predicate_recursively

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: rustc 1.30.0-nightly (6e0f1cc15 2018-09-05) running on x86_64-unknown-linux-gnu

error: Could not document `typenum`.

Caused by:
  process didn't exit successfully: `rustdoc --crate-name typenum /home/wardsegers/.cargo/registry/src/github.com-1ecc6299db9ec823/typenum-1.10.0/src/lib.rs --cap-lints allow -o /home/wardsegers/git/origami/origami_web/target/doc -L dependency=/home/wardsegers/git/origami/origami_web/target/debug/deps` (exit code: 1)

[frol]

I confirm this bug since at least Rust Nightly 2018-08-15.

You can reproduce it with the following repo: https://github.com/qbit-org-ua/lolcoin-2018/

$ env RUST_BACKTRACE=1 cargo +nightly doc --open
...
error: internal compiler error: librustc/traits/structural_impls.rs:178: impossible case reached

thread '<unnamed>' panicked at 'Box<Any>', librustc_errors/lib.rs:587:9
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:71
             at libstd/sys_common/backtrace.rs:59
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:211
   3: std::panicking::default_hook
             at libstd/panicking.rs:227
   4: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:477
   5: std::panicking::begin_panic
   6: rustc_errors::Handler::bug
   7: rustc::util::bug::opt_span_bug_fmt::{{closure}}
   8: rustc::ty::context::tls::with_opt::{{closure}}
   9: rustc::ty::context::tls::with_context_opt
  10: rustc::ty::context::tls::with_opt
  11: rustc::util::bug::opt_span_bug_fmt
  12: rustc::util::bug::bug_fmt
  13: rustc::traits::structural_impls::<impl rustc::ty::context::Lift<'tcx> for rustc::traits::SelectionError<'a>>::lift_to_tcx
  14: rustc::ty::context::TyCtxt::lift_to_global
  15: rustc::traits::select::SelectionContext::candidate_from_obligation
  16: rustc::traits::select::SelectionContext::evaluate_stack
  17: rustc::dep_graph::graph::DepGraph::with_anon_task
  18: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  19: rustc::infer::InferCtxt::probe
  20: <&'a mut I as core::iter::iterator::Iterator>::next
  21: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  22: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  23: rustc::dep_graph::graph::DepGraph::with_anon_task
  24: rustc::traits::select::SelectionContext::candidate_from_obligation
  25: rustc::traits::select::SelectionContext::evaluate_stack
  26: rustc::dep_graph::graph::DepGraph::with_anon_task
  27: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  28: rustc::infer::InferCtxt::probe
  29: <&'a mut I as core::iter::iterator::Iterator>::next
  30: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  31: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  32: rustc::dep_graph::graph::DepGraph::with_anon_task
  33: rustc::traits::select::SelectionContext::candidate_from_obligation
  34: rustc::traits::select::SelectionContext::evaluate_stack
  35: rustc::dep_graph::graph::DepGraph::with_anon_task
  36: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  37: rustc::infer::InferCtxt::probe
  38: <&'a mut I as core::iter::iterator::Iterator>::next
  39: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  40: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  41: rustc::dep_graph::graph::DepGraph::with_anon_task
  42: rustc::traits::select::SelectionContext::candidate_from_obligation
  43: rustc::traits::select::SelectionContext::evaluate_stack
  44: rustc::dep_graph::graph::DepGraph::with_anon_task
  45: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  46: rustc::infer::InferCtxt::probe
  47: <&'a mut I as core::iter::iterator::Iterator>::next
  48: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  49: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  50: rustc::dep_graph::graph::DepGraph::with_anon_task
  51: rustc::traits::select::SelectionContext::candidate_from_obligation
  52: rustc::traits::select::SelectionContext::evaluate_stack
  53: rustc::dep_graph::graph::DepGraph::with_anon_task
  54: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  55: rustc::infer::InferCtxt::probe
  56: <&'a mut I as core::iter::iterator::Iterator>::next
  57: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  58: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  59: rustc::dep_graph::graph::DepGraph::with_anon_task
  60: rustc::traits::select::SelectionContext::candidate_from_obligation
  61: rustc::traits::select::SelectionContext::evaluate_stack
  62: rustc::dep_graph::graph::DepGraph::with_anon_task
  63: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  64: rustc::infer::InferCtxt::probe
  65: <&'a mut I as core::iter::iterator::Iterator>::next
  66: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  67: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  68: rustc::dep_graph::graph::DepGraph::with_anon_task
  69: rustc::traits::select::SelectionContext::candidate_from_obligation
  70: rustc::traits::select::SelectionContext::evaluate_stack
  71: rustc::dep_graph::graph::DepGraph::with_anon_task
  72: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  73: rustc::infer::InferCtxt::probe
  74: <&'a mut I as core::iter::iterator::Iterator>::next
  75: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  76: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  77: rustc::dep_graph::graph::DepGraph::with_anon_task
  78: rustc::traits::select::SelectionContext::candidate_from_obligation
  79: rustc::traits::select::SelectionContext::evaluate_stack
  80: rustc::dep_graph::graph::DepGraph::with_anon_task
  81: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  82: rustc::infer::InferCtxt::probe
  83: <&'a mut I as core::iter::iterator::Iterator>::next
  84: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  85: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  86: rustc::dep_graph::graph::DepGraph::with_anon_task
  87: rustc::traits::select::SelectionContext::candidate_from_obligation
  88: rustc::traits::select::SelectionContext::evaluate_stack
  89: rustc::dep_graph::graph::DepGraph::with_anon_task
  90: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  91: rustc::infer::InferCtxt::probe
  92: <&'a mut I as core::iter::iterator::Iterator>::next
  93: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  94: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  95: rustc::dep_graph::graph::DepGraph::with_anon_task
  96: rustc::traits::select::SelectionContext::candidate_from_obligation
  97: rustc::traits::select::SelectionContext::evaluate_stack
  98: rustc::dep_graph::graph::DepGraph::with_anon_task
  99: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
    Checking mio-uds v0.6.7

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: rustc 1.30.0-nightly (2d4e34ca8 2018-09-09) running on x86_64-unknown-linux-gnu

error: Could not document `typenum`.

Caused by:
  process didn't exit successfully: `rustdoc --crate-name typenum /home/frol/.cargo/registry/src/github.com-1ecc6299db9ec823/typenum-1.10.0/src/lib.rs --cap-lints allow -o /mnt/storage/projects/qbit/LOL-2018/lolcoin/target/doc -L dependency=/mnt/storage/projects/qbit/LOL-2018/lolcoin/target/debug/deps` (exit code: 1)
...

[waywardmonkeys]

I think this is the same as #53505 and was fixed in #54199 which is in the current nightly.

[jesskfullwood]

Don't think this has been fixed - I just hit it while compiling differential-dataflow, running the latest nightly.

Edit: Looking at the stack traces, not certain that I have hit the same error

$ rustc --version
rustc 1.31.0-nightly (f99911a4a 2018-10-23)

$ RUST_BACKTRACE=1 cargo doc --open
 Documenting differential-dataflow v0.7.0                                                               
error: internal compiler error: librustc/traits/select.rs:2764: Where clause `Binder(<_ as std::marker::Send>)` was applicable to `Obligation(predicate=Binder(TraitPredicate(<operators::ValueHistory<'_, _, _, _> as std::marker::Send>)),depth=2)` but now is not
                                                                                                        
thread '<unnamed>' panicked at 'Box<Any>', librustc_errors/lib.rs:600:9                                 
stack backtrace:                                                                                        
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace                                         
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49                                           
   1: std::sys_common::backtrace::print                                                                 
             at libstd/sys_common/backtrace.rs:71                                                       
             at libstd/sys_common/backtrace.rs:59                                                       
   2: std::panicking::default_hook::{{closure}}                                                         
             at libstd/panicking.rs:211                                                                 
   3: std::panicking::default_hook                                                                      
             at libstd/panicking.rs:227                                                                 
   4: std::panicking::rust_panic_with_hook                                                              
             at libstd/panicking.rs:476                                                                 
   5: std::panicking::begin_panic                                                                       
   6: rustc_errors::Handler::bug                                                                        
   7: rustc::util::bug::opt_span_bug_fmt::{{closure}}                                                   
   8: rustc::ty::context::tls::with_opt::{{closure}}                                                    
   9: rustc::ty::context::tls::with_context_opt                                                         
  10: rustc::ty::context::tls::with_opt                                                                 
  11: rustc::util::bug::opt_span_bug_fmt                                                                
  12: rustc::util::bug::bug_fmt                                                                         
  13: rustc::traits::select::SelectionContext::confirm_candidate                                        
  14: rustc::infer::InferCtxt::probe                                                                    
  15: rustc::traits::select::SelectionContext::evaluate_stack                                           
  16: rustc::dep_graph::graph::DepGraph::with_anon_task                                                 
  17: rustc::traits::select::SelectionContext::evaluate_predicate_recursively                           
  18: rustc::infer::InferCtxt::probe                                                                    
  19: rustc::traits::select::SelectionContext::evaluate_stack                                           
  20: rustc::dep_graph::graph::DepGraph::with_anon_task                                                 
  21: rustc::traits::select::SelectionContext::evaluate_predicate_recursively                           
  22: rustc::infer::InferCtxt::probe                                                                    
  23: rustc::traits::select::SelectionContext::evaluate_stack                                           
  24: rustc::dep_graph::graph::DepGraph::with_anon_task                                                 
  25: rustc::traits::select::SelectionContext::evaluate_predicate_recursively                           
  26: rustc::traits::select::SelectionContext::evaluate_obligation_recursively                          
  27: rustc::ty::context::GlobalCtxt::enter_local                                                       
  28: rustc_traits::evaluate_obligation::evaluate_obligation                                            
  29: rustc::ty::query::__query_compute::evaluate_obligation                                            
  30: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::evaluate_obligation<'tcx>>::compute
  31: rustc::dep_graph::graph::DepGraph::with_task_impl                                                 
  32: rustc::ty::context::tls::with_related_context                                                     
  33: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job
  34: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query          
  35: rustc::traits::query::evaluate_obligation::<impl rustc::infer::InferCtxt<'cx, 'gcx, 'tcx>>::evaluate_obligation
  36: rustc::ty::context::tls::with_context::{{closure}}                                                
             at librustdoc/clean/blanket_impl.rs:110                                                    
             at librustc/infer/mod.rs:526                                                               
             at librustc/ty/context.rs:1670                                                             
             at librustc/ty/context.rs:2016                                                             
             at librustc/ty/context.rs:1955                                                             
             at librustc/ty/context.rs:2015                                                             
             at librustc/ty/context.rs:1669                                                             
             at librustc/ty/context.rs:2116                                                             
             at librustc/ty/context.rs:2100                                                             
  37: rustc::ty::context::GlobalCtxt::enter_local                                                       
             at librustc/ty/context.rs:2091                                                             
             at librustc/ty/context.rs:2100                                                             
             at librustc/ty/context.rs:2111                                                             
             at librustc/ty/context.rs:1662                                                             
  38: rustdoc::clean::blanket_impl::BlanketImplFinder::get_blanket_impls::{{closure}}                   
             at librustc/infer/mod.rs:525                                                               
             at librustdoc/clean/blanket_impl.rs:80                                                     
  39: rustc::ty::trait_def::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::for_each_relevant_impl   
             at librustc/ty/trait_def.rs:106                                                            
  40: rustdoc::clean::blanket_impl::BlanketImplFinder::get_blanket_impls                                
             at librustdoc/clean/blanket_impl.rs:79                                                     
  41: rustdoc::clean::def_ctor::get_def_from_node_id                                                    
             at librustdoc/clean/blanket_impl.rs:42                                                     
             at librustdoc/clean/def_ctor.rs:59                                                         
  42: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector<'a, 'tcx, 'rcx, 'cstore> as rustdoc::fold::DocFolder>::fold_item
             at librustdoc/clean/blanket_impl.rs:40                                                     
             at librustdoc/clean/mod.rs:3364                                                            
             at librustdoc/passes/collect_trait_impls.rs:171                                            
  43: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                   
             at librustdoc/fold.rs:61                                                                   
             at libcore/iter/mod.rs:1640                                                                
             at liballoc/vec.rs:1908                                                                    
             at liballoc/vec.rs:1805                                                                    
             at liballoc/vec.rs:1800                                                                    
  44: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                   
  45: rustdoc::fold::DocFolder::fold_inner_recur                                                        
             at liballoc/vec.rs:1700                                                                    
             at libcore/iter/iterator.rs:1476                                                           
             at librustdoc/fold.rs:110                                                                  
             at librustdoc/fold.rs:37                                                                   
  46: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector<'a, 'tcx, 'rcx, 'cstore> as rustdoc::fold::DocFolder>::fold_item
             at librustdoc/fold.rs:100                                                                  
             at librustdoc/passes/collect_trait_impls.rs:178                                            
  47: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                   
             at librustdoc/fold.rs:61                                                                   
             at libcore/iter/mod.rs:1640                                                                
             at liballoc/vec.rs:1908                                                                    
             at liballoc/vec.rs:1805                                                                    
             at liballoc/vec.rs:1800                                                                    
  48: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                   
  49: rustdoc::fold::DocFolder::fold_inner_recur                                                        
             at liballoc/vec.rs:1700                                                                    
             at libcore/iter/iterator.rs:1476                                                           
             at librustdoc/fold.rs:110                                                                  
             at librustdoc/fold.rs:37                                                                   
  50: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector<'a, 'tcx, 'rcx, 'cstore> as rustdoc::fold::DocFolder>::fold_item
             at librustdoc/fold.rs:100                                                                  
             at librustdoc/passes/collect_trait_impls.rs:178                                            
  51: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                   
             at librustdoc/fold.rs:61                                                                   
             at libcore/iter/mod.rs:1640                                                                
             at liballoc/vec.rs:1908                                                                    
             at liballoc/vec.rs:1805                                                                    
             at liballoc/vec.rs:1800                                                                    
  52: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                   
  53: rustdoc::fold::DocFolder::fold_inner_recur                                                        
             at liballoc/vec.rs:1700                                                                    
             at libcore/iter/iterator.rs:1476                                                           
             at librustdoc/fold.rs:110                                                                  
             at librustdoc/fold.rs:37                                                                   
  54: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector<'a, 'tcx, 'rcx, 'cstore> as rustdoc::fold::DocFolder>::fold_item
             at librustdoc/fold.rs:100                                                                  
             at librustdoc/passes/collect_trait_impls.rs:178                                            
  55: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                   
             at librustdoc/fold.rs:61                                                                   
             at libcore/iter/mod.rs:1640                                                                
             at liballoc/vec.rs:1908                                                                    
             at liballoc/vec.rs:1805                                                                    
             at liballoc/vec.rs:1800                                                                    
  56: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                   
  57: rustdoc::fold::DocFolder::fold_inner_recur                                                        
             at liballoc/vec.rs:1700                                                                    
             at libcore/iter/iterator.rs:1476                                                           
             at librustdoc/fold.rs:110                                                                  
             at librustdoc/fold.rs:37                                                                   
  58: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector<'a, 'tcx, 'rcx, 'cstore> as rustdoc::fold::DocFolder>::fold_item
             at librustdoc/fold.rs:100                                                                  
             at librustdoc/passes/collect_trait_impls.rs:178                                            
  59: rustdoc::passes::collect_trait_impls::collect_trait_impls                                         
             at librustdoc/fold.rs:115                                                                  
             at libcore/option.rs:632                                                                   
             at librustdoc/fold.rs:115                                                                  
             at librustdoc/passes/collect_trait_impls.rs:26                                             
  60: rustdoc::core::run_core::{{closure}}::{{closure}}                                                 
             at librustdoc/core.rs:614                                                                  
  61: rustc::ty::context::tls::enter_context                                                            
             at librustc_driver/driver.rs:1353                                                          
             at librustc/ty/context.rs:2048                                                             
             at librustc/ty/context.rs:2016                                                             
             at librustc/ty/context.rs:1955                                                             
             at librustc/ty/context.rs:2015                                                             
  62: <std::thread::local::LocalKey<T>>::with                                                           
             at librustc/ty/context.rs:2047                                                             
             at librustc/ty/context.rs:2005                                                             
             at libstd/thread/local.rs:300                                                              
             at libstd/thread/local.rs:254                                                              
             at librustc/ty/context.rs:1997                                                             
             at libstd/thread/local.rs:300                                                              
             at libstd/thread/local.rs:254                                                              
  63: rustc::ty::context::TyCtxt::create_and_enter                                                      
             at librustc/ty/context.rs:1989                                                             
             at librustc/ty/context.rs:2027                                                             
             at librustc/ty/context.rs:1243                                                             
  64: rustc_driver::driver::phase_3_run_analysis_passes                                                 
             at librustc_driver/driver.rs:1261                                                          
  65: <scoped_tls::ScopedKey<T>>::set                                                                   
             at librustdoc/core.rs:496                                                                  
             at librustc_driver/driver.rs:76                                                            
             at /cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:155         
  66: rustdoc::core::run_core                                                                           
             at librustc_driver/driver.rs:75                                                            
             at librustdoc/core.rs:405                                                                  
  67: <scoped_tls::ScopedKey<T>>::set                                                                   
             at librustdoc/lib.rs:720                                                                   
             at /cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:155         
             at libsyntax/lib.rs:106                                                                    
             at /cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:155         
  68: syntax::with_globals                                                                              
             at libsyntax/lib.rs:105                                                                    
  69: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once                   
             at librustdoc/lib.rs:716                                                                   
             at librustc_driver/lib.rs:1632                                                             
             at libstd/panic.rs:313                                                                     
  70: std::panicking::try::do_call                                                                      
             at libstd/panicking.rs:310                                                                 
  71: __rust_maybe_catch_panic                                                                          
             at libpanic_unwind/lib.rs:102                                                              
  72: rustc_driver::monitor                                                                             
             at libstd/panicking.rs:289                                                                 
             at libstd/panic.rs:392                                                                     
             at librustc_driver/lib.rs:1546                                                             
             at librustc_driver/lib.rs:1557                                                             
             at librustc_driver/lib.rs:1631                                                             
  73: rustdoc::rust_input                                                                               
             at librustdoc/lib.rs:716                                                                   
  74: rustdoc::main_args                                                                                
             at librustdoc/lib.rs:613                                                                   
             at librustdoc/lib.rs:568                                                                   
  75: <scoped_tls::ScopedKey<T>>::set                                                                   
             at librustdoc/lib.rs:115                                                                   
             at libcore/option.rs:424                                                                   
             at librustdoc/lib.rs:115                                                                   
             at /cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:155         
             at libsyntax/lib.rs:106                                                                    
             at /cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:155         
  76: syntax::with_globals                                                                              
             at libsyntax/lib.rs:105                                                                    
  77: std::panicking::try::do_call                                                                      
             at libstd/thread/mod.rs:409                                                                
             at libstd/panic.rs:313                                                                     
             at libstd/panicking.rs:310                                                                 
  78: __rust_maybe_catch_panic                                                                          
             at libpanic_unwind/lib.rs:102                                                              
  79: <F as alloc::boxed::FnBox<A>>::call_box                                                           
             at libstd/panicking.rs:289                                                                 
             at libstd/panic.rs:392                                                                     
             at libstd/thread/mod.rs:408                                                                
             at liballoc/boxed.rs:672                                                                   
  80: std::sys_common::thread::start_thread                                                             
             at liballoc/boxed.rs:682                                                                   
             at libstd/sys_common/thread.rs:24                                                          
  81: std::sys::unix::thread::Thread::new::thread_start                                                 
             at libstd/sys/unix/thread.rs:90                                                            
  82: start_thread                                                                                      
  83: __clone                    

[Aaron1011]

@jesskfullwood That issue appears to be fixed as of rustdoc 1.31.0-nightly (cae6efc37 2018-10-27)

[jesskfullwood]

It seems so. Fixed by #55258? Thanks!

[editicalu]

I don't see the issue anymore. I'll close the issue.