Rustdoc ICE with invalid intra rustdoc links

[yvt]

The following code including an intra rustdoc link (#43466) crashes cargo doc ( rustc 1.29.0-nightly (874dec25e 2018-07-21)):

pub type TypeAlias = usize;

/// [broken cross-reference](TypeAlias::hoge)
pub fn some_public_item() {}

With the following output:

 Documenting my_crate_name v0.1.0 (file:///my_crate_path/my_crate_name)
error: internal compiler error: librustc_typeck/collect.rs:605: impossible case reached

thread '<unnamed>' panicked at 'Box<Any>', librustc_errors/lib.rs:557:9
stack backtrace:
   0:        0x1057e418f - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::hcf8349fe897fa63a
   1:        0x1057bcd7a - std::sys_common::backtrace::print::hc274b78279f04e86
   2:        0x1057ebe73 - std::panicking::default_hook::{{closure}}::h559649071ca4adf8
   3:        0x1057ebbfc - std::panicking::default_hook::h1face3b5a352fe07
   4:        0x1057ec567 - std::panicking::rust_panic_with_hook::h4a24ff63f41e4491
   5:        0x10545a9e3 - std::panicking::begin_panic::hb3b4e0ec5512d348
   6:        0x1054565dc - rustc_errors::Handler::bug::h5e0086bc217b083f
   7:        0x103cb37e5 - rustc::session::opt_span_bug_fmt::{{closure}}::ha9978bb031dd11f8
   8:        0x103d7740c - rustc::ty::context::tls::with_opt::{{closure}}::h8d6cb447391bb8e8
   9:        0x103cb4758 - rustc::ty::context::tls::with_context_opt::h62d27409a047b21f
  10:        0x103d769f4 - rustc::ty::context::tls::with_opt::h2329e2eea4064820
  11:        0x103c2a524 - rustc::session::opt_span_bug_fmt::h68f7fa6347afcc10
  12:        0x103c2a471 - rustc::session::bug_fmt::ha3175f83d2fd7481
  13:        0x10295ed9c - rustc_typeck::collect::adt_def::h5dfd917dc1af3c10
  14:        0x103caa513 - rustc::ty::query::__query_compute::adt_def::hc61482ce28b518db
  15:        0x103d77bce - rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::adt_def<'tcx>>::compute::h8efb93d059bba9b7
  16:        0x103b947be - rustc::dep_graph::graph::DepGraph::with_task_impl::h8224618827541074
  17:        0x103d26505 - rustc::ty::context::tls::with_related_context::h5a3fb8a4ab1cb4a6
  18:        0x103e634f1 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job::hc774e6a77bed00a2
  19:        0x103f047a5 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query::h91e1c033d60db51b
  20:        0x103f74251 - rustc::ty::query::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::adt_def::hc753efab5ec9b088
  21:        0x101d98ce1 - rustdoc::clean::resolve::h064b9f991dec1289
  22:        0x101f40140 - <[syntax::ast::Attribute] as rustdoc::clean::Clean<rustdoc::clean::Attributes>>::clean::h1280074b449e8ef6
  23:        0x101d703da - <rustdoc::doctree::Function as rustdoc::clean::Clean<rustdoc::clean::Item>>::clean::hd24feff5180643a1
  24:        0x101e36a89 - <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::spec_extend::h4873bf57266aed7b
  25:        0x101d6f780 - <rustdoc::doctree::Module as rustdoc::clean::Clean<rustdoc::clean::Item>>::clean::hfa56c6ec84a0fad6
  26:        0x101d6eaa0 - <rustdoc::visit_ast::RustdocVisitor<'a, 'tcx, 'rcx> as rustdoc::clean::Clean<rustdoc::clean::Crate>>::clean::hb505941fd365de06
  27:        0x101d78a25 - rustdoc::core::run_core::{{closure}}::{{closure}}::h2554b93fbfd8c6da
  28:        0x101d65560 - rustc::ty::context::tls::enter_context::h8f956fd3652c2ae0
  29:        0x101d3009c - <std::thread::local::LocalKey<T>>::with::hef786ae88d33cd4b
  30:        0x101f631ba - rustc::ty::context::TyCtxt::create_and_enter::h7cf93880cc7015c4
  31:        0x101e0b3f9 - rustdoc::core::run_core::{{closure}}::he0b0f25298972ae7
  32:        0x101e0865f - rustdoc::core::run_core::h828fe8bce5a57617
  33:        0x101dddf7c - <scoped_tls::ScopedKey<T>>::set::h633ed2611e15d386
  34:        0x101f655b2 - syntax::with_globals::h04795d255090029c
  35:        0x101d50e99 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::h705fbad8fa6e1908
  36:        0x101d2b31d - std::panicking::try::do_call::h746a094a3cb63158
  37:        0x1057f8bbe - __rust_maybe_catch_panic
  38:        0x101ddca2e - rustc_driver::monitor::h67b9e3e5157c1aac
  39:        0x101f6f31f - rustdoc::rust_input::hac3bfc9eb4508126
  40:        0x101f6d798 - rustdoc::main_args::hed174c4fe9b47bb0
  41:        0x101ddfe2f - <scoped_tls::ScopedKey<T>>::set::hb0c5b0cee373eba1
  42:        0x101f6566d - syntax::with_globals::h1a242def3fb86fc2
  43:        0x101d2b27d - std::panicking::try::do_call::h54d7b1301bf90714
  44:        0x1057f8bbe - __rust_maybe_catch_panic
  45:        0x101d40389 - <F as alloc::boxed::FnBox<A>>::call_box::hadeefd2a5638fe74
  46:        0x1057bba6b - std::sys::unix::thread::Thread::new::thread_start::hdf37fcc49f83810c
  47:     0x7fff7e9a4660 - _pthread_body
  48:     0x7fff7e9a450c - _pthread_start

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 1.29.0-nightly (874dec25e 2018-07-21) running on x86_64-apple-darwin

error: Could not document `my_crate_name`.

Caused by:
  process didn't exit successfully: `rustdoc --crate-name my_crate_name src/lib.rs -o /my_crate_path/my_crate_name/target/doc -L dependency=/my_crate_path/my_crate_name/target/debug/deps` (exit code: 1)

Meta

rustc --version --verbose:

rustc 1.29.0-nightly (874dec25e 2018-07-21)
binary: rustc
commit-hash: 874dec25ed4c08d36f17d396b6872ca50313fc8e
commit-date: 2018-07-21
host: x86_64-apple-darwin
release: 1.29.0-nightly
LLVM version: 7.0

[GuillaumeGomez]

I think it's actually the @rust-lang/compiler which should handle this bug since it's coming from TyCtxt.

[varkor]

As far as I can tell the issue is that when rustdoc is looking up an associated item here:
https://github.com/rust-lang/rust/blob/a8b9e678772f04614288b5f8fe44001c7626ab70/src/librustdoc/clean/mod.rs#L1198-L1199
It includes Def::TyAlias. But later in the else branch of this condition:
https://github.com/rust-lang/rust/blob/a8b9e678772f04614288b5f8fe44001c7626ab70/src/librustdoc/clean/mod.rs#L1215-L1223
It calls adt_def, which does not handle type aliases:
https://github.com/rust-lang/rust/blob/a8b9e678772f04614288b5f8fe44001c7626ab70/src/librustc_typeck/collect.rs#L605
rustdoc should be dereferencing the type alias to the type it is aliasing and calling adt_def on that.

[GuillaumeGomez]

Thanks @varkor! I'll take a look into it.

[eddyb]

You want to match on tcx.type_of(did) and probably not interact with adt_def at all.