Panic while documenting nalgebra

[waywardmonkeys]

When using the nightly with the bugfix for the problems with typenum, this error happens when trying to document the nalgebra crate:

note: rustc 1.31.0-nightly (de3d640 2018-10-01) running on x86_64-apple-darwin

 Documenting nalgebra v0.16.4 (/Users/bruce/Development/custodian/nalgebra)                                                                                                                                                            
error: internal compiler error: librustc/traits/select.rs:2531: Where clause `Binder(<base::default_allocator::DefaultAllocator as base::allocator::Allocator<_, _>>)` was applicable to `Obligation(predicate=Binder(TraitPredicate(<base::default_allocator::DefaultAllocator as base::allocator::Allocator<_, _, _>>)),depth=3)` but now is not
                                                                                                                                                                                                                                              
thread '<unnamed>' panicked at 'Box<Any>', librustc_errors/lib.rs:599:9                                                                                                                                                                       
stack backtrace:                                                                                                                                                                                                                              
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace                                                                                                                                                                               
   1: std::sys_common::backtrace::print                                                                                                                                                                                                       
   2: std::panicking::default_hook::{{closure}}                                                                                                                                                                                               
   3: std::panicking::default_hook                                                                                                                                                                                                            
   4: std::panicking::rust_panic_with_hook                                                                                                                                                                                                    
   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: <&'a mut I as core::iter::iterator::Iterator>::next                                                                                                                                                                                     
  20: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                                                                                                                                                         
  21: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache                                                                                                                                                             
  22: rustc::dep_graph::graph::DepGraph::with_anon_task                                                                                                                                                                                       
  23: rustc::traits::select::SelectionContext::candidate_from_obligation                                                                                                                                                                      
  24: rustc::traits::select::SelectionContext::evaluate_stack                                                                                                                                                                                 
  25: rustc::dep_graph::graph::DepGraph::with_anon_task                                                                                                                                                                                       
  26: rustc::traits::select::SelectionContext::evaluate_predicate_recursively                                                                                                                                                                 
  27: rustc::infer::InferCtxt::probe                                                                                                                                                                                                          
  28: rustc::traits::select::SelectionContext::evaluate_stack                                                                                                                                                                                 
  29: rustc::dep_graph::graph::DepGraph::with_anon_task                                                                                                                                                                                       
  30: rustc::traits::select::SelectionContext::evaluate_predicate_recursively                                                                                                                                                                 
  31: rustc::infer::InferCtxt::probe                                                                                                                                                                                                          
  32: rustc::traits::select::SelectionContext::evaluate_stack                                                                                                                                                                                 
  33: rustc::dep_graph::graph::DepGraph::with_anon_task                                                                                                                                                                                       
  34: rustc::traits::select::SelectionContext::evaluate_predicate_recursively                                                                                                                                                                 
  35: rustc::traits::select::SelectionContext::evaluate_obligation_recursively                                                                                                                                                                
  36: rustc::ty::context::tls::with_related_context                                                                                                                                                                                           
  37: rustc::infer::InferCtxtBuilder::enter                                                                                                                                                                                                   
  38: rustc_traits::evaluate_obligation::evaluate_obligation                                                                                                                                                                                  
  39: rustc::ty::query::__query_compute::evaluate_obligation                                                                                                                                                                                  
  40: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::evaluate_obligation<'tcx>>::compute                                                                                               
  41: rustc::dep_graph::graph::DepGraph::with_task_impl                                                                                                                                                                                       
  42: rustc::ty::context::tls::with_related_context                                                                                                                                                                                           
  43: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job                                                                                                                                     
  44: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query                                                                                                                                                
  45: rustc::traits::query::evaluate_obligation::<impl rustc::infer::InferCtxt<'cx, 'gcx, 'tcx>>::evaluate_obligation                                                                                                                         
  46: rustc::ty::context::tls::with_context::{{closure}}                                                                                                                                                                                      
  47: rustdoc::clean::blanket_impl::BlanketImplFinder::get_blanket_impls::{{closure}}                                                                                                                                                         
  48: rustc::ty::trait_def::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::for_each_relevant_impl                                                                                                                                         
  49: rustdoc::clean::blanket_impl::BlanketImplFinder::get_blanket_impls                                                                                                                                                                      
  50: rustdoc::clean::def_ctor::get_def_from_node_id                                                                                                                                                                                          
  51: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector<'a, 'tcx, 'rcx, 'cstore> as rustdoc::fold::DocFolder>::fold_item                                                                                                          
  52: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                                                                                                                                                         
  53: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                                                                                                                                                         
  54: rustdoc::fold::DocFolder::fold_inner_recur                                                                                                                                                                                              
  55: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector<'a, 'tcx, 'rcx, 'cstore> as rustdoc::fold::DocFolder>::fold_item                                                                                                          
  56: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                                                                                                                                                         
  57: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter                                                                                                                                                                         
  58: rustdoc::fold::DocFolder::fold_inner_recur                                                                                                                                                                                              
  59: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector<'a, 'tcx, 'rcx, 'cstore> as rustdoc::fold::DocFolder>::fold_item                                                                                                          
  60: rustdoc::passes::collect_trait_impls::collect_trait_impls                                                                                                                                                                               
  61: rustdoc::core::run_core::{{closure}}::{{closure}}                                                                                                                                                                                       
  62: rustc::ty::context::tls::enter_context                                                                                                                                                                                                  
  63: <std::thread::local::LocalKey<T>>::with                                                                                                                                                                                                 
  64: rustc::ty::context::TyCtxt::create_and_enter                                                                                                                                                                                            
  65: rustc_driver::driver::phase_3_run_analysis_passes                                                                                                                                                                                       
  66: <scoped_tls::ScopedKey<T>>::set                                                                                                                                                                                                         
  67: rustdoc::core::run_core                                                                                                                                                                                                                 
  68: <scoped_tls::ScopedKey<T>>::set                                                                                                                                                                                                         
  69: syntax::with_globals                                                                                                                                                                                                                    
  70: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once                                                                                                                                                         
  71: std::panicking::try::do_call                                                                                                                                                                                                            
  72: __rust_maybe_catch_panic                                                                                                                                                                                                                
  73: rustc_driver::monitor                                                                                                                                                                                                                   
  74: rustdoc::rust_input                                                                                                                                                                                                                     
  75: rustdoc::main_args                                                                                                                                                                                                                      
  76: <scoped_tls::ScopedKey<T>>::set                                                                                                                                                                                                         
  77: syntax::with_globals                                                                                                                                                                                                                    
  78: std::panicking::try::do_call                                                                                                                                                                                                            
  79: __rust_maybe_catch_panic                                                                                                                                                                                                                
  80: <F as alloc::boxed::FnBox<A>>::call_box                                                                                                                                                                                                 
  81: std::sys_common::thread::start_thread                                                                                                                                                                                                   
  82: std::sys::unix::thread::Thread::new::thread_start                                                                                                                                                                                       
  83: _pthread_body                                                                                                                                                                                                                           
  84: _pthread_start                                                                                                                                                                                                                          

[waywardmonkeys]

cc: @sebcrozet FYI

[izzabelle]

it seemed to document fine for me on the most recent nightly build

[Aaron1011]

This is fixed as of rustdoc 1.31.0-nightly (cae6efc37 2018-10-27)

[steveklabnik]

Closing then! Thanks! :D

[waywardmonkeys]

Will this need backporting at all?