save-analysis: ICE when name resolution fails

[nrc]

STR: run with -Zsave-analysis on a program with a name resolution error. Result:

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', src/libcore/option.rs:323
stack backtrace:
   1:        0x10608efe8 - std::sys::backtrace::tracing::imp::write::he09d58d1497100a9
   2:        0x106096faf - std::panicking::default_hook::{{closure}}::hf3f7aa526824ae88
   3:        0x1060952e5 - std::panicking::default_hook::h691f7ee16f920a74
   4:        0x106095a06 - std::panicking::rust_panic_with_hook::haa794968064098e8
   5:        0x1060958a4 - std::panicking::begin_panic::h78b83f343fc429be
   6:        0x1060957c2 - std::panicking::begin_panic_fmt::h8b3207332f403a68
   7:        0x106095727 - rust_begin_unwind
   8:        0x1060c3af0 - core::panicking::panic_fmt::h5cca666ac160c125
   9:        0x1060c39f4 - core::panicking::panic::h30a00c8dd89101b4
  10:        0x10471f109 - <rustc_save_analysis::dump_visitor::DumpVisitor<'l, 'tcx, 'll, D> as syntax::visit::Visitor>::visit_expr::h163cde99c278fc43
  11:        0x1046f10ce - <rustc_save_analysis::dump_visitor::DumpVisitor<'l, 'tcx, 'll, D>>::process_method::h04468bf911ce2542
  12:        0x104701439 - <rustc_save_analysis::dump_visitor::DumpVisitor<'l, 'tcx, 'll, D>>::process_impl_item::h4e762d98295a5e48
  13:        0x104705074 - <rustc_save_analysis::dump_visitor::DumpVisitor<'l, 'tcx, 'll, D> as syntax::visit::Visitor>::visit_item::h02ded85bb6033cf8
  14:        0x1047327aa - rustc_save_analysis::process_crate::he5e07bdf3c6cb726
  15:        0x103bed73b - <rustc_driver::RustcDefaultCalls as rustc_driver::CompilerCalls<'a>>::build_controller::{{closure}}::{{closure}}::hbf39625416cfff33
  16:        0x103bf2071 - <rustc_driver::RustcDefaultCalls as rustc_driver::CompilerCalls<'a>>::build_controller::{{closure}}::h858ba59f1e3b27b9
  17:        0x103bee6df - rustc_driver::driver::compile_input::{{closure}}::h273cad8b7f8d1024
  18:        0x103be7813 - rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}::h7ce10fd09281598f
  19:        0x103bb5036 - rustc_driver::driver::phase_3_run_analysis_passes::he8ee46117275842d
  20:        0x103ba2f9a - rustc_driver::driver::compile_input::h0271fc4a3333b327
  21:        0x103bc98e9 - rustc_driver::run_compiler::h1315ba568dec0ab8
  22:        0x1036be10d - rls::build::BuildQueue::rustc::{{closure}}::{{closure}}::h66962e2240eaa638
  23:        0x1036bd8ca - rustc_driver::run::{{closure}}::h6946deb7d8e0395b
  24:        0x1036be2c3 - rustc_driver::monitor::{{closure}}::hd1ab9dd35d21c63f
  25:        0x10365457b - <std::panic::AssertUnwindSafe<F> as core::ops::FnOnce<()>>::call_once::ha448607329ef3916
  26:        0x1034bce26 - std::panicking::try::do_call::h4d4051ea56bb4a02
  27:        0x10609756a - __rust_maybe_catch_panic
  28:        0x1034bac10 - std::panicking::try::h8f6846036d1a2b63
  29:        0x1034ae735 - std::panic::catch_unwind::ha11e26ecdbf248e3
  30:        0x1036c32a1 - std::thread::Builder::spawn::{{closure}}::h6b4547929665b7b8
  31:        0x1035208a0 - <F as alloc::boxed::FnBox<A>>::call_box::h7d5e87dbc610ebb6
  32:        0x106094a54 - std::sys::thread::Thread::new::thread_start::h2d239c26e84b740e
  33:     0x7fff9a8bdaba - _pthread_body
  34:     0x7fff9a8bda06 - _pthread_start

cc rust-lang/rls#41 (bug manifests in the RLS)

[eulerdisk]

I can take this. I already dug into librustc_save_analysis some time ago, I encountered the same bug when I was trying to write a refactoring tool.
To fix the issue, I have to remove all the span_bug around there, right ?

[nrc]

@eulerdisk great, thanks for digging in.

There's likely to be some span_bugs that don't need to be there, but it won't be quite as simple as just ripping them out. There will be some error condition that needs to be dealt with.