Rustdoc ICE when collecting intra-doc links

[Michael-F-Bryan]

I found an ICE when trying to document the spirit-log crate on the latest nightly.

Skimming through the backtrace, it looks like rustdoc::clean::inline::record_extern_fqn accessed an invalid index while traversing links within rustdoc::passes::collect_intra_doc_links::collect_intra_doc_links.

Steps to reproduce:

$ cd /tmp
$ git clone git@github.com:vorner/spirit.git  
Cloning into 'spirit'...
remote: Enumerating objects: 40, done.
remote: Counting objects: 100% (40/40), done.
remote: Compressing objects: 100% (33/33), done.
remote: Total 3182 (delta 9), reused 11 (delta 2), pack-reused 3142
Receiving objects: 100% (3182/3182), 1019.71 KiB | 1.10 MiB/s, done.
Resolving deltas: 100% (1890/1890), done.
$ cd spirit/spirit-log
$ git checkout 7c52608689fd1488c26ccaa0520e9dd926e7501c
$ uname -a
Linux laptop 5.0.0-32-generic #34-Ubuntu SMP Wed Oct 2 02:06:48 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
$ rustc --version --verbose
rustc 1.40.0-nightly (246be7e1a 2019-10-25)
binary: rustc
commit-hash: 246be7e1a557b8ac8287c6842379a0db67770be6
commit-date: 2019-10-25
host: x86_64-unknown-linux-gnu
release: 1.40.0-nightly
LLVM version: 9.0
$ cargo --version --verbose
cargo 1.40.0-nightly (3ba5f2717 2019-10-22)
release: 1.40.0
commit-hash: 3ba5f27170db10af7a92f2b682e049397197b8fa
commit-date: 2019-10-22
$ RUST_BACKTRACE=full cargo doc
 Documenting spirit v0.4.0 (/tmp/spirit)
warning: `[crate::log_error]` cannot be resolved, ignoring it...
   --> src/lib.rs:453:20
    |
453 | //! [`log_error`]: macro@crate::log_error
    |                    ^^^^^^^^^^^^^^^^^^^^^^ cannot be resolved, ignoring
    |
    = note: `#[warn(intra_doc_link_resolution_failure)]` on by default
    = help: to escape `[` and `]` characters, just add '\' before them like `\[` or `\]`

thread 'rustc' panicked at 'index out of bounds: the len is 40 but the index is 40', /rustc/246be7e1a557b8ac8287c6842379a0db67770be6/src/libcore/slice/mod.rs:2796:10
stack backtrace:
   0:     0x7ff9a3a45014 - backtrace::backtrace::libunwind::trace::hab3225e15f119ae0
                               at /cargo/registry/src/git.luolix.top-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/libunwind.rs:88
   1:     0x7ff9a3a45014 - backtrace::backtrace::trace_unsynchronized::hbaf4bc94065e3599
                               at /cargo/registry/src/git.luolix.top-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/mod.rs:66
   2:     0x7ff9a3a45014 - std::sys_common::backtrace::_print_fmt::hbee4e41845713fe0
                               at src/libstd/sys_common/backtrace.rs:77
   3:     0x7ff9a3a45014 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hb733ceb939af72e6
                               at src/libstd/sys_common/backtrace.rs:61
   4:     0x7ff9a3a7d58c - core::fmt::write::h6610df6b014c1fa3
                               at src/libcore/fmt/mod.rs:1028
   5:     0x7ff9a3a393f7 - std::io::Write::write_fmt::h38d85ee16f610932
                               at src/libstd/io/mod.rs:1412
   6:     0x7ff9a3a4983e - std::sys_common::backtrace::_print::h061c5d660abcf8d1
                               at src/libstd/sys_common/backtrace.rs:65
   7:     0x7ff9a3a4983e - std::sys_common::backtrace::print::hc28d1c154d74f5b9
                               at src/libstd/sys_common/backtrace.rs:50
   8:     0x7ff9a3a4983e - std::panicking::default_hook::{{closure}}::h53bff1f7c2aed77d
                               at src/libstd/panicking.rs:188
   9:     0x7ff9a3a49541 - std::panicking::default_hook::hf02412a75b646f46
                               at src/libstd/panicking.rs:205
  10:     0x7ff9a3a4a01c - std::panicking::rust_panic_with_hook::h9226e8f020e126d7
                               at src/libstd/panicking.rs:472
  11:     0x7ff9a3a49ad2 - std::panicking::continue_panic_fmt::hdf2b5cc8fe9d1e3b
                               at src/libstd/panicking.rs:375
  12:     0x7ff9a3a499c6 - rust_begin_unwind
                               at src/libstd/panicking.rs:302
  13:     0x7ff9a3a770fa - core::panicking::panic_fmt::h794f55f0674340d0
                               at src/libcore/panicking.rs:84
  14:     0x7ff9a3a770b5 - core::panicking::panic_bounds_check::h64960dc7d578ef8d
                               at src/libcore/panicking.rs:61
  15:     0x7ff9a53eb464 - rustc_metadata::cstore_impl::<impl rustc::middle::cstore::CrateStore for rustc_metadata::cstore::CStore>::crate_data_as_any::h87dcab865adcdf0f
  16:     0x7ff9a53510eb - rustc_metadata::cstore_impl::provide_extern::crate_name::h0cc0624b2d4e6ceb
  17:     0x558f283c4bf5 - rustc::ty::query::__query_compute::crate_name::ha39afb20634a4f73
  18:     0x558f281a196d - rustc::dep_graph::graph::DepGraph::with_task_impl::hf35e82810c3323b8
  19:     0x558f28296539 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query::hb6252697cb67bd63
  20:     0x558f283717b8 - rustdoc::clean::inline::record_extern_fqn::hc1fa57ee322c2fed
  21:     0x558f283dbdb4 - rustdoc::clean::register_res::habd605d2ad378dad
  22:     0x558f281b2edb - <rustdoc::passes::collect_intra_doc_links::LinkCollector as rustdoc::fold::DocFolder>::fold_item::hdaf2eac19e0789e6
  23:     0x558f28209f49 - <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter::h405df7c23303ea9c
  24:     0x558f281a26c6 - rustdoc::fold::DocFolder::fold_inner_recur::h9d8c41801488ba12
  25:     0x558f281a3386 - rustdoc::fold::DocFolder::fold_item_recur::hc7107c01ae876a28
  26:     0x558f281b579a - <rustdoc::passes::collect_intra_doc_links::LinkCollector as rustdoc::fold::DocFolder>::fold_item::hdaf2eac19e0789e6
  27:     0x558f28209f49 - <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter::h405df7c23303ea9c
  28:     0x558f281a26c6 - rustdoc::fold::DocFolder::fold_inner_recur::h9d8c41801488ba12
  29:     0x558f281a3386 - rustdoc::fold::DocFolder::fold_item_recur::hc7107c01ae876a28
  30:     0x558f281b579a - <rustdoc::passes::collect_intra_doc_links::LinkCollector as rustdoc::fold::DocFolder>::fold_item::hdaf2eac19e0789e6
  31:     0x558f281b5eb7 - <rustdoc::passes::collect_intra_doc_links::LinkCollector as rustdoc::fold::DocFolder>::fold_crate::h5d79100f4dec5efd
  32:     0x558f281afebb - rustdoc::passes::collect_intra_doc_links::collect_intra_doc_links::hde2b2e326618ebd5
  33:     0x558f28238976 - rustc::ty::context::tls::enter_global::hc78871115590302e
  34:     0x558f282b5ce7 - rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}}::h38489c11c78915c2
  35:     0x7ff9a42cfb7a - rustc_interface::passes::create_global_ctxt::{{closure}}::hb862dbb4d2ca887a
  36:     0x558f282b5972 - rustc_interface::passes::BoxedGlobalCtxt::enter::hd8b6203cb3e50951
  37:     0x558f28379b6a - rustdoc::core::run_core::hd924c9677a0f5ecd
  38:     0x558f28227940 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::hc921e38d2a98e856
  39:     0x558f283520cb - std::panicking::try::do_call::h54d3c25b1f4a03c4
  40:     0x7ff9a3a5a8ba - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:80
  41:     0x558f283ab09b - rustc_driver::catch_fatal_errors::hef91d7f5a3f99d5f
  42:     0x558f281b8d7a - rustdoc::main_options::h96b421dcabb1372f
  43:     0x558f283059b5 - std::thread::local::LocalKey<T>::with::haa8ef269ff0079b5
  44:     0x558f282b1d4e - scoped_tls::ScopedKey<T>::set::h5ad613cd4536582c
  45:     0x558f283c8d62 - syntax::with_globals::h16e602af63553392
  46:     0x558f2822ac0d - std::sys_common::backtrace::__rust_begin_short_backtrace::ha20ec3782fd09249
  47:     0x7ff9a3a5a8ba - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:80
  48:     0x558f2822d0f9 - core::ops::function::FnOnce::call_once{{vtable.shim}}::hc22b265702fb1f87
  49:     0x7ff9a3a2b44f - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h048fda3ebc391397
                               at /rustc/246be7e1a557b8ac8287c6842379a0db67770be6/src/liballoc/boxed.rs:942
  50:     0x7ff9a3a592e0 - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h76e6cb3f56f40d59
                               at /rustc/246be7e1a557b8ac8287c6842379a0db67770be6/src/liballoc/boxed.rs:942
  51:     0x7ff9a3a592e0 - std::sys_common::thread::start_thread::ha21bc807781f4e78
                               at src/libstd/sys_common/thread.rs:13
  52:     0x7ff9a3a592e0 - std::sys::unix::thread::Thread::new::thread_start::hc839a9e9b07e2e92
                               at src/libstd/sys/unix/thread.rs:79
  53:     0x7ff9a39a5182 - start_thread
  54:     0x7ff9a38b2b1f - __clone
  55:                0x0 - <unknown>
error: Could not document `spirit`.

Caused by:
  process didn't exit successfully: `rustdoc --edition=2018 --crate-type lib --crate-name spirit src/lib.rs -o /tmp/spirit/target/doc --cfg 'feature="cfg-help"' --cfg 'feature="structdoc"' --error-format=json --json=diagnostic-rendered-ansi -L dependency=/tmp/spirit/target/debug/deps --extern arc_swap=/tmp/spirit/target/debug/deps/libarc_swap-74733a42b4d0d636.rmeta --extern config_spirit_fork=/tmp/spirit/target/debug/deps/libconfig_spirit_fork-0dc6526fffa8645b.rmeta --extern either=/tmp/spirit/target/debug/deps/libeither-3c6baf0ffbfa146d.rmeta --extern err_context=/tmp/spirit/target/debug/deps/liberr_context-351c3e6ca14163b9.rmeta --extern fallible_iterator=/tmp/spirit/target/debug/deps/libfallible_iterator-5f4a8f111b20530a.rmeta --extern humantime=/tmp/spirit/target/debug/deps/libhumantime-a10ea5b619150980.rmeta --extern libc=/tmp/spirit/target/debug/deps/liblibc-b0e85993139d10b9.rmeta --extern log=/tmp/spirit/target/debug/deps/liblog-2fe4ad0f0ad43e6b.rmeta --extern serde=/tmp/spirit/target/debug/deps/libserde-8107fdb3ca0f691a.rmeta --extern serde_ignored=/tmp/spirit/target/debug/deps/libserde_ignored-6b5329bf097aa317.rmeta --extern serde_path_to_error=/tmp/spirit/target/debug/deps/libserde_path_to_error-36b50dc734fe2764.rmeta --extern signal_hook=/tmp/spirit/target/debug/deps/libsignal_hook-5a1f3fcdcb7b3bcc.rmeta --extern structdoc=/tmp/spirit/target/debug/deps/libstructdoc-4dc490ea500ee6bd.rmeta --extern structopt=/tmp/spirit/target/debug/deps/libstructopt-c187231a4ba3078a.rmeta --extern toml=/tmp/spirit/target/debug/deps/libtoml-e98a6f8df07be7cc.rmeta` (exit code: 1)

[GuillaumeGomez]

Taking a look.

[GuillaumeGomez]

Actually, it's failing outside of rustdoc so I prefer to let someone else handle it.

cc @rust-lang/compiler

[kinnison]

I think this might be a rustdoc bug (or at least mismatch between how rustdoc uses the resolver infrastructure and how it's meant to work). See my comment here: #66159 (comment)