rustdoc: failed to normalize

[matthiaskrgr]

Code

./tests/ui/union/projection-as-union-type-error.rs

#![crate_type = "lib"]

pub trait Identity {
    type Identity;
}

pub type Foo = u8;

pub union Bar {
    a:  <Foo as Identity>::Identity, //~ ERROR
    b: u8,
}

Meta

rustc --version --verbose:

Regression in #106938

Error output

<output>

Backtrace

error: internal compiler error: compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:198:90: Failed to normalize <u8 as Identity>::Identity, maybe try to call `try_normalize_erasing_regions` instead

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/compiler/rustc_errors/src/lib.rs:1644:9
stack backtrace:
   0:     0x7f5a7c76a56a - std::backtrace_rs::backtrace::libunwind::trace::h96288e3e31cede0c
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f5a7c76a56a - std::backtrace_rs::backtrace::trace_unsynchronized::h136276fcc921ebd2
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f5a7c76a56a - std::sys_common::backtrace::_print_fmt::hed1407344e09c3c5
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7f5a7c76a56a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hef11c1a0e2ccbd67
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f5a7c7caa3e - core::fmt::write::h9d34c1ab82e0e30d
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/core/src/fmt/mod.rs:1232:17
   5:     0x7f5a7c75ab35 - std::io::Write::write_fmt::h583f259fb2d64e4c
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/io/mod.rs:1684:15
   6:     0x7f5a7c76a335 - std::sys_common::backtrace::_print::h384b5154a89856a1
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7f5a7c76a335 - std::sys_common::backtrace::print::he3caeede32862700
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7f5a7c76d0ff - std::panicking::default_hook::{{closure}}::hb37cdcd49b812817
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/panicking.rs:267:22
   9:     0x7f5a7c76ce3b - std::panicking::default_hook::h89fa77719af1b8c7
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/panicking.rs:286:9
  10:     0x7f5a7fa84824 - rustc_driver_impl[996a7fa2764f51ac]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7f5a7c76d93a - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hcdabce48acce76a1
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/alloc/src/boxed.rs:2002:9
  12:     0x7f5a7c76d93a - std::panicking::rust_panic_with_hook::h420ef2d822c4b069
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/panicking.rs:692:13
  13:     0x7f5a800051c1 - std[cd98010995c1c111]::panicking::begin_panic::<rustc_errors[aee54022d4af98b8]::ExplicitBug>::{closure#0}
  14:     0x7f5a800050d6 - std[cd98010995c1c111]::sys_common::backtrace::__rust_end_short_backtrace::<std[cd98010995c1c111]::panicking::begin_panic<rustc_errors[aee54022d4af98b8]::ExplicitBug>::{closure#0}, !>
  15:     0x7f5a7ff87a96 - std[cd98010995c1c111]::panicking::begin_panic::<rustc_errors[aee54022d4af98b8]::ExplicitBug>
  16:     0x7f5a800224b6 - std[cd98010995c1c111]::panic::panic_any::<rustc_errors[aee54022d4af98b8]::ExplicitBug>
  17:     0x7f5a80020686 - <rustc_errors[aee54022d4af98b8]::HandlerInner>::bug::<&alloc[d5203ca4bbacc4a0]::string::String>
  18:     0x7f5a80020360 - <rustc_errors[aee54022d4af98b8]::Handler>::bug::<&alloc[d5203ca4bbacc4a0]::string::String>
  19:     0x7f5a8003f38b - rustc_middle[dd44835e384dc8fc]::util::bug::opt_span_bug_fmt::<rustc_span[c7747b3aedb35767]::span_encoding::Span>::{closure#0}
  20:     0x7f5a8003e64a - rustc_middle[dd44835e384dc8fc]::ty::context::tls::with_opt::<rustc_middle[dd44835e384dc8fc]::util::bug::opt_span_bug_fmt<rustc_span[c7747b3aedb35767]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7f5a8003e616 - rustc_middle[dd44835e384dc8fc]::ty::context::tls::with_context_opt::<rustc_middle[dd44835e384dc8fc]::ty::context::tls::with_opt<rustc_middle[dd44835e384dc8fc]::util::bug::opt_span_bug_fmt<rustc_span[c7747b3aedb35767]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7f5a8003f2d6 - rustc_middle[dd44835e384dc8fc]::util::bug::opt_span_bug_fmt::<rustc_span[c7747b3aedb35767]::span_encoding::Span>
  23:     0x7f5a7ddc9b43 - rustc_middle[dd44835e384dc8fc]::util::bug::bug_fmt
  24:     0x7f5a7dc5e1f1 - <rustc_middle[dd44835e384dc8fc]::ty::normalize_erasing_regions::NormalizeAfterErasingRegionsFolder as rustc_middle[dd44835e384dc8fc]::ty::fold::TypeFolder>::fold_ty
  25:     0x7f5a7e46478a - rustc_hir_analysis[fafe05592f4b0540]::check::check::check_mod_item_types
  26:     0x7f5a7efbe711 - rustc_query_system[1e3d87d6bb1db1ab]::query::plumbing::try_execute_query::<rustc_query_impl[f65b45c65392aba7]::queries::check_mod_item_types, rustc_query_impl[f65b45c65392aba7]::plumbing::QueryCtxt>
  27:     0x7f5a7f41c9ad - <rustc_query_impl[f65b45c65392aba7]::Queries as rustc_middle[dd44835e384dc8fc]::ty::query::QueryEngine>::check_mod_item_types
  28:     0x55b7efad374a - <rustc_middle[dd44835e384dc8fc]::hir::map::Map>::for_each_module::<rustdoc[78efbd2992aca86b]::core::run_global_ctxt::{closure#0}::{closure#0}>
  29:     0x55b7efcc14c2 - <rustc_session[8b3af3d4e67ba61e]::session::Session>::time::<(), rustdoc[78efbd2992aca86b]::core::run_global_ctxt::{closure#0}>
  30:     0x55b7efd0bdc6 - rustdoc[78efbd2992aca86b]::core::run_global_ctxt
  31:     0x55b7efcc078c - <rustc_session[8b3af3d4e67ba61e]::session::Session>::time::<(rustdoc[78efbd2992aca86b]::clean::types::Crate, rustdoc[78efbd2992aca86b]::config::RenderOptions, rustdoc[78efbd2992aca86b]::formats::cache::Cache), rustdoc[78efbd2992aca86b]::main_args::{closure#1}::{closure#0}::{closure#1}::{closure#0}>
  32:     0x55b7efbfceaf - <rustc_interface[82796a5553273f34]::passes::QueryContext>::enter::<rustdoc[78efbd2992aca86b]::main_args::{closure#1}::{closure#0}::{closure#1}, core[c2ed83ad2149f92c]::result::Result<(), rustc_errors[aee54022d4af98b8]::ErrorGuaranteed>>
  33:     0x55b7efb71f07 - <rustc_interface[82796a5553273f34]::interface::Compiler>::enter::<rustdoc[78efbd2992aca86b]::main_args::{closure#1}::{closure#0}, core[c2ed83ad2149f92c]::result::Result<(), rustc_errors[aee54022d4af98b8]::ErrorGuaranteed>>
  34:     0x55b7efc15d69 - std[cd98010995c1c111]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[82796a5553273f34]::util::run_in_thread_pool_with_globals<rustc_interface[82796a5553273f34]::interface::run_compiler<core[c2ed83ad2149f92c]::result::Result<(), rustc_errors[aee54022d4af98b8]::ErrorGuaranteed>, rustdoc[78efbd2992aca86b]::main_args::{closure#1}>::{closure#0}, core[c2ed83ad2149f92c]::result::Result<(), rustc_errors[aee54022d4af98b8]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[c2ed83ad2149f92c]::result::Result<(), rustc_errors[aee54022d4af98b8]::ErrorGuaranteed>>
  35:     0x55b7efd81b4d - <<std[cd98010995c1c111]::thread::Builder>::spawn_unchecked_<rustc_interface[82796a5553273f34]::util::run_in_thread_pool_with_globals<rustc_interface[82796a5553273f34]::interface::run_compiler<core[c2ed83ad2149f92c]::result::Result<(), rustc_errors[aee54022d4af98b8]::ErrorGuaranteed>, rustdoc[78efbd2992aca86b]::main_args::{closure#1}>::{closure#0}, core[c2ed83ad2149f92c]::result::Result<(), rustc_errors[aee54022d4af98b8]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[c2ed83ad2149f92c]::result::Result<(), rustc_errors[aee54022d4af98b8]::ErrorGuaranteed>>::{closure#1} as core[c2ed83ad2149f92c]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  36:     0x7f5a7c777933 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h125a8995d683d283
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/alloc/src/boxed.rs:1988:9
  37:     0x7f5a7c777933 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hc8d7e704b7a14a23
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/alloc/src/boxed.rs:1988:9
  38:     0x7f5a7c777933 - std::sys::unix::thread::Thread::new::thread_start::hc8f4f2c9b0ce4632
                               at /rustc/8996ea93b6e554148c4286e62b613f12a3ee505c/library/std/src/sys/unix/thread.rs:108:17
  39:     0x7f5a7c5088fd - <unknown>
  40:     0x7f5a7c58ad20 - <unknown>
  41:                0x0 - <unknown>

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 1.69.0-nightly (8996ea93b 2023-02-09) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [check_mod_item_types] checking item types in top-level module
end of query stack
error: aborting due to previous error

[oli-obk]

Considering this errors with rustc, and rustdoc can only document rust code that actually compiles, I'd say this is in the same bucket as the other issues we have open about this, meaning "not a bug, just a papercut"?

[jyn514]

rustdoc can only document rust code that actually compiles

this is not true

https://doc.rust-lang.org/beta/rustdoc/advanced-features.html#interactions-between-platform-specific-docs

[oli-obk]

I can only document code that compiles, ignoring method bodies. This specific test has no method bodies, so does it fall under that rule?

[jyn514]

That seems possible, but you should test to make sure. Rustdoc's logic around this is extremely janky and indirect.

[matthiaskrgr]

What is the benefit of documenting code that does not compile?

[jyn514]

I can't keep having this argument. Please read the documentation.

[jyn514]

cc #79496 (comment)