ICE: rustdoc unwrap `None` when documenting dependency with GATs #94009

[MingweiSamuel]

Code

Code here, big project, but only need to run -p kvs or -p relalg to cause the error. Maybe will try to minimize later.
hydro-project/hydro@d39d44d

Minimized example: https://github.com/MingweiSamuel/rustdoc-ice

my_dependency/src/lib.rs

#![feature(generic_associated_types)]

pub trait MyTrait {
    type MyGat<'s>
    where
        Self: 's;
    fn my_fn(&self) -> Self::MyGat<'_>;
}

impl MyTrait for () {
    type MyGat<'s> = &'s ();
    fn my_fn(&self) -> Self::MyGat<'_> {
        &()
    }
}

my_package/src/lib.rs

use my_dependency;

Command:

cargo doc

Meta

• Platform: x86_64-pc-windows-msvc
• Regression in nightly-2022-03-05
• Regression in 6d7684101a51f1c375ec84aef5d2fbdeb214bbc2 6d76841
• Support GATs in Rustdoc #94009
• 6d76841#diff-384affc1b4190940f114f3fcebbf969e7e18657a71ef9001da6b223a036687d9R409

Error output

See backtrace

Backtrace

$ cargo doc
    Checking my_dependency v0.1.0 (D:\Projects\rustdoc-ice\my_dependency)
 Documenting my_dependency v0.1.0 (D:\Projects\rustdoc-ice\my_dependency)
 Documenting my_package v0.1.0 (D:\Projects\rustdoc-ice\my_package)
thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', src\librustdoc\clean\mod.rs:409:59
stack backtrace:
   0:     0x7ff999ab9740 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1b60d32e13dca2c0
   1:     0x7ff999aef5ba - core::fmt::write::h956db761fb8891bc
   2:     0x7ff999aabe99 - <std::io::IoSliceMut as core::fmt::Debug>::fmt::h8bae511bb1c52660
   3:     0x7ff999abcd0b - std::panicking::default_hook::h400a469cdf1f53e7
   4:     0x7ff999abc8ec - std::panicking::default_hook::h400a469cdf1f53e7
   5:     0x7ff9912b9726 - rustc_driver[96d5aea7497e3b44]::pretty::print_after_hir_lowering
   6:     0x7ff999abd5eb - std::panicking::rust_panic_with_hook::haf3e9c505f20c32c
   7:     0x7ff999abd302 - <std::panicking::begin_panic_handler::StrPanicPayload as core::panic::BoxMeUp>::get::hf200192ef50e8b12
   8:     0x7ff999aba057 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1b60d32e13dca2c0
   9:     0x7ff999abd019 - rust_begin_unwind
  10:     0x7ff999b22ab5 - core::panicking::panic_fmt::h600d95c087b9120e
  11:     0x7ff999b2295c - core::panicking::panic::h4922a2ba3330589b
  12:     0x7ff6c097a9ce - <unknown>
  13:     0x7ff6c09d5355 - <unknown>
  14:     0x7ff6c0b340ef - <unknown>
  15:     0x7ff6c0923cb4 - <unknown>
  16:     0x7ff6c0af4249 - <unknown>
  17:     0x7ff6c0b373b4 - <unknown>
  18:     0x7ff6c0995c86 - <unknown>
  19:     0x7ff6c09d9d88 - <unknown>
  20:     0x7ff6c0a89f50 - <unknown>
  21:     0x7ff6c0a9c98b - <unknown>
  22:     0x7ff6c0924e41 - <unknown>
  23:     0x7ff6c0ae2059 - <unknown>
  24:     0x7ff6c0aa162e - <unknown>
  25:     0x7ff6c08e5332 - <unknown>
  26:     0x7ff6c0b4ccf5 - <unknown>
  27:     0x7ff6c0a5936c - <unknown>
  28:     0x7ff6c0b4fd0f - <unknown>
  29:     0x7ff6c084ba08 - <unknown>
  30:     0x7ff6c0b74247 - <unknown>
  31:     0x7ff6c08b7168 - <unknown>
  32:     0x7ff999acc6dc - std::sys::windows::thread::Thread::new::h0128d9e8937707db
  33:     0x7ffa02817034 - BaseThreadInitThunk
  34:     0x7ffa02c02651 - RtlUserThreadStart

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.61.0-nightly (c274e4969 2022-03-05) running on x86_64-pc-windows-msvc

note: compiler flags: --crate-type lib

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
error: could not document `my_package`

Caused by:
  process didn't exit successfully: `rustdoc --edition=2021 --crate-type lib --crate-name my_package 'my_package\src\lib.rs' -o 'D:\Projects\rustdoc-ice\target\doc' --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat -C metadata=3198935b0623bdb3 -L 'dependency=D:\Projects\rustdoc-ice\target\debug\deps' --extern 'my_dependency=D:\Projects\rustdoc-ice\target\debug\deps\libmy_dependency-190dee38e23bdfd7.rmeta' --crate-version 0.1.0` 
(exit code: 101)

[compiler-errors]

I'll look into it!

@rustbot claim

[compiler-errors]

Minimized this to a local-crate-only test, and working on a solution currently:

#![feature(generic_associated_types)]

pub trait Trait {
    type Gat<'a>;
}

pub type T = fn(&<() as Trait>::Gat<'_>);