[ICE]: `exit_elem` called on empty class stack parent

[madsmtm]

winit v0.30.13's documentation is failing to build on newer Rust versions, see docs.rs and rust-windowing/winit#4511.

Seems to be some weird interaction between Cargo features and macros? I'm not quite sure.

Code

https://github.com/madsmtm/rustdoc-winit-bug contains the full minification, reproduced here too:

src/lib.rs:

pub struct Window {}

impl Window {
    pub fn id(&self) -> u64 {
        todo!()
    }
}

examples/window.rs:

#![allow(dead_code)]
use rustdoc_winit_bug::Window;
use tracing::info;

struct WindowState {
    window: Window,
}

impl WindowState {
    fn takes_ref(&self) {
        info!("{:?}", self.window.id());
    }

    fn takes_mut(&mut self) {
        info!("{:?}", self.window.id());
    }
}

fn main() {}

Cargo.toml:

[workspace]

[package]
edition = "2024"
name = "rustdoc-winit-bug"
version = "0.1.0"

[dependencies]
tracing = { version = "0.1.40", default-features = false }

[dev-dependencies]
tracing = { version = "0.1.40", default-features = false, features = ["log"] }

[[example]]
doc-scrape-examples = true
name = "window"

Run with:

cargo +nightly-2026-03-13 rustdoc -Zunstable-options -Zrustdoc-scrape-examples

Backtrace

Backtrace

thread 'rustc' panicked at src/librustdoc/html/highlight.rs:234:42:
`exit_elem` called on empty class stack parent
stack backtrace:
   0:        0x114a88958 - <std[5e4cd47ac048545]::backtrace::Backtrace>::create
   1:        0x1128f2854 - std[5e4cd47ac048545]::panicking::update_hook::<alloc[f0aa43b5a48e9af6]::boxed::Box<rustc_driver_impl[9810d8d61b400d2c]::install_ice_hook::{closure#1}>>::{closure#0}
   2:        0x114a99f94 - std[5e4cd47ac048545]::panicking::panic_with_hook
   3:        0x114a7debc - std[5e4cd47ac048545]::panicking::panic_handler::{closure#0}
   4:        0x114a74860 - std[5e4cd47ac048545]::sys::backtrace::__rust_end_short_backtrace::<std[5e4cd47ac048545]::panicking::panic_handler::{closure#0}, !>
   5:        0x114a7f48c - __rustc[528297b2bcb02c92]::rust_begin_unwind
   6:        0x117aba5f0 - core[cc6e5097f7e6aa90]::panicking::panic_fmt
   7:        0x117aba2f4 - core[cc6e5097f7e6aa90]::option::expect_failed
   8:        0x104d8fc24 - rustdoc[455d8d6df7ffa9da]::html::highlight::write_code::<core[cc6e5097f7e6aa90]::fmt::Formatter>::{closure#2}
   9:        0x104e95af8 - rustdoc[455d8d6df7ffa9da]::html::highlight::classify
  10:        0x104cec7e8 - rustdoc[455d8d6df7ffa9da]::html::highlight::write_code::<core[cc6e5097f7e6aa90]::fmt::Formatter>
  11:        0x104f2c884 - <&core[cc6e5097f7e6aa90]::fmt::builders::FromFn<rustdoc[455d8d6df7ffa9da]::html::sources::print_src<&mut core[cc6e5097f7e6aa90]::fmt::Formatter>::{closure#0}> as core[cc6e5097f7e6aa90]::fmt::Display>::fmt
  12:        0x111c82c20 - core[cc6e5097f7e6aa90]::fmt::write
  13:        0x104f2cc50 - <&askama[22ea555c962af5c5]::filters::escape::Safe<&core[cc6e5097f7e6aa90]::fmt::builders::FromFn<rustdoc[455d8d6df7ffa9da]::html::sources::print_src<&mut core[cc6e5097f7e6aa90]::fmt::Formatter>::{closure#0}>> as core[cc6e5097f7e6aa90]::fmt::Display>::fmt
  14:        0x111c82c20 - core[cc6e5097f7e6aa90]::fmt::write
  15:        0x104d8ebd4 - rustdoc[455d8d6df7ffa9da]::html::render::render_call_locations::<&mut core[cc6e5097f7e6aa90]::fmt::Formatter>::{closure#2}
  16:        0x104f5d4a8 - <core[cc6e5097f7e6aa90]::fmt::builders::FromFn<rustdoc[455d8d6df7ffa9da]::html::render::document_full_inner::{closure#0}> as core[cc6e5097f7e6aa90]::fmt::Display>::fmt
  17:        0x104c5d5a4 - rustdoc[455d8d6df7ffa9da]::html::render::render_impl::{closure#0}::doc_impl_item::<&mut alloc[f0aa43b5a48e9af6]::string::String, &mut alloc[f0aa43b5a48e9af6]::string::String>
  18:        0x104f5a58c - <core[cc6e5097f7e6aa90]::fmt::builders::FromFn<rustdoc[455d8d6df7ffa9da]::html::render::render_impl::{closure#0}> as core[cc6e5097f7e6aa90]::fmt::Display>::fmt
  19:        0x104e91814 - rustdoc[455d8d6df7ffa9da]::html::render::render_assoc_items_inner
  20:        0x104f5ced8 - <core[cc6e5097f7e6aa90]::fmt::builders::FromFn<rustdoc[455d8d6df7ffa9da]::html::render::render_assoc_items::{closure#0}> as core[cc6e5097f7e6aa90]::fmt::Display>::fmt
  21:        0x111c82c20 - core[cc6e5097f7e6aa90]::fmt::write
  22:        0x104c45590 - <rustdoc[455d8d6df7ffa9da]::html::render::print_item::DisplayStruct>::render_into::<core[cc6e5097f7e6aa90]::fmt::Formatter>
  23:        0x104f60c2c - <core[cc6e5097f7e6aa90]::fmt::builders::FromFn<rustdoc[455d8d6df7ffa9da]::html::render::print_item::item_struct::{closure#0}> as core[cc6e5097f7e6aa90]::fmt::Display>::fmt
  24:        0x111c82c20 - core[cc6e5097f7e6aa90]::fmt::write
  25:        0x104ce7c18 - rustdoc[455d8d6df7ffa9da]::html::layout::render::<core[cc6e5097f7e6aa90]::fmt::builders::FromFn<rustdoc[455d8d6df7ffa9da]::html::render::print_item::print_item::{closure#0}>, core[cc6e5097f7e6aa90]::fmt::builders::FromFn<<rustdoc[455d8d6df7ffa9da]::html::render::context::Context>::render_item::{closure#1}>>
  26:        0x104df6a0c - <rustdoc[455d8d6df7ffa9da]::html::render::context::Context>::render_item
  27:        0x104f44214 - <rustdoc[455d8d6df7ffa9da]::html::render::context::Context as rustdoc[455d8d6df7ffa9da]::formats::renderer::FormatRenderer>::item
  28:        0x104ceea2c - rustdoc[455d8d6df7ffa9da]::formats::renderer::run_format_inner::<rustdoc[455d8d6df7ffa9da]::html::render::context::Context>
  29:        0x104ceebf4 - rustdoc[455d8d6df7ffa9da]::formats::renderer::run_format_inner::<rustdoc[455d8d6df7ffa9da]::html::render::context::Context>
  30:        0x104d94658 - rustdoc[455d8d6df7ffa9da]::main_args::{closure#2}::{closure#0}
  31:        0x104d8bdfc - rustc_interface[96ebfdf40f9119ad]::interface::run_compiler::<(), rustdoc[455d8d6df7ffa9da]::main_args::{closure#2}>::{closure#1}
  32:        0x104cf59c8 - std[5e4cd47ac048545]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[96ebfdf40f9119ad]::util::run_in_thread_with_globals<rustc_interface[96ebfdf40f9119ad]::util::run_in_thread_pool_with_globals<rustc_interface[96ebfdf40f9119ad]::interface::run_compiler<(), rustdoc[455d8d6df7ffa9da]::main_args::{closure#2}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  33:        0x104dbe64c - <std[5e4cd47ac048545]::thread::lifecycle::spawn_unchecked<rustc_interface[96ebfdf40f9119ad]::util::run_in_thread_with_globals<rustc_interface[96ebfdf40f9119ad]::util::run_in_thread_pool_with_globals<rustc_interface[96ebfdf40f9119ad]::interface::run_compiler<(), rustdoc[455d8d6df7ffa9da]::main_args::{closure#2}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[cc6e5097f7e6aa90]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  34:        0x114aa4c50 - <std[5e4cd47ac048545]::sys::thread::unix::Thread>::new::thread_start
  35:        0x195e43bc8 - __pthread_cond_wait


rustc version: 1.96.0-nightly (3102493c7 2026-03-12)
platform: aarch64-apple-darwin

query stack during panic:
end of query stack

[madsmtm]

searched nightlies: from nightly-2025-10-24 to nightly-2025-12-05
regressed nightly: nightly-2025-10-27
searched commit range: 34f954f...f37aa99
regressed commit: f977dfc

bisected with cargo-bisect-rustc v0.6.11

Host triple: aarch64-apple-darwin
Reproduce with:

cargo bisect-rustc --start 1.92.0 --end 1.93.0 -- rustdoc -Zunstable-options -Zrustdoc-scrape-examples 

Seems to have regressed in #146992, CC @GuillaumeGomez @yotamofek @lolbinarycat

[madsmtm]

Seems similar to #148184 (except that one is fixed).

[GuillaumeGomez]

Thanks for the minified code! Gonna take a look in the next days.

[khalidsaidi]

A2ABench has an accepted answer for this imported thread.

• Thread: https://a2abench-api.web.app/q/cmmpdq83i00hq6t5upp7c9ucl
• Accepted at: 2026-03-13T22:14:51.912Z
• Accepted answer agent: live-ans-bulk-1773439863
• Answer preview: "External agent resolution:\n\n1. Reproduce.\n2. Isolate root cause.\n3. Patch smallest surface.\n4. Verify with one negative and one positive test."