[ICE]: rustdoc: `unexpected const parent in type_of(): TraitRef ..`

[matthiaskrgr]

Code

use std::ops::Generator;

fn gen() -> impl Generator<{}> {}

Affected release channels

• Previous Stable
• Current Stable
• Current Beta
• Current Nightly

Rust Version

rustc 1.68.0-nightly (333ee6c46 2023-01-18)
binary: rustc
commit-hash: 333ee6c466972185973d5097f8b5fb0f9fb13fa5
commit-date: 2023-01-18
host: x86_64-unknown-linux-gnu
release: 1.68.0-nightly
LLVM version: 15.0.6

Current error output

No response

Backtrace

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: unexpected const parent in type_of(): TraitRef(TraitRef { path: Path { span: a.rs:3:18: 3:31 (#0), res: Def(Trait, DefId(2:2969 ~ core[830d]::ops::generator::Generator)), segments: [PathSegment { ident: Generator#0, hir_id: HirId(DefId(0:6 ~ a[6282]::gen::{opaque#0}).4), res: Def(Trait, DefId(2:2969 ~ core[830d]::ops::generator::Generator)), args: Some(GenericArgs { args: [Const(ConstArg { value: AnonConst { hir_id: HirId(DefId(0:6 ~ a[6282]::gen::{opaque#0}).1), def_id: DefId(0:5 ~ a[6282]::gen::{constant#0}), body: BodyId { hir_id: HirId(DefId(0:6 ~ a[6282]::gen::{opaque#0}).2) } }, span: a.rs:3:28: 3:30 (#0) })], bindings: [], parenthesized: false, span_ext: a.rs:3:27: 3:31 (#0) }), infer_args: false }] }, hir_ref_id: HirId(DefId(0:6 ~ a[6282]::gen::{opaque#0}).5) })
  |
  = note: delayed at    0: <rustc_errors::HandlerInner>::emit_diagnostic
             1: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
             2: <rustc_middle::ty::context::TyCtxt>::ty_error_with_message::<rustc_span::span_encoding::Span>
             3: rustc_hir_analysis::collect::type_of::type_of
             4: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::type_of, rustc_query_impl::plumbing::QueryCtxt, rustc_middle::dep_graph::dep_node::DepKind>
             5: rustdoc::clean::clean_const
             6: <core::iter::adapters::map::Map<core::slice::iter::Iter<rustc_hir::hir::GenericArg>, rustdoc::clean::clean_generic_args::{closure#1}> as core::iter::traits::iterator::Iterator>::fold::<(), core::iter::traits::iterator::Iterator::for_each::call<rustdoc::clean::types::GenericArg, <alloc::vec::Vec<rustdoc::clean::types::GenericArg>>::extend_trusted<core::iter::adapters::map::Map<core::slice::iter::Iter<rustc_hir::hir::GenericArg>, rustdoc::clean::clean_generic_args::{closure#1}>>::{closure#0}>::{closure#0}>
             7: <alloc::vec::Vec<rustdoc::clean::types::GenericArg> as alloc::vec::spec_from_iter::SpecFromIter<rustdoc::clean::types::GenericArg, core::iter::adapters::map::Map<core::slice::iter::Iter<rustc_hir::hir::GenericArg>, rustdoc::clean::clean_generic_args::{closure#1}>>>::from_iter
             8: rustdoc::clean::clean_generic_args
             9: <thin_vec::ThinVec<rustdoc::clean::types::PathSegment> as core::iter::traits::collect::FromIterator<rustdoc::clean::types::PathSegment>>::from_iter::<core::iter::adapters::map::Map<core::slice::iter::Iter<rustc_hir::hir::PathSegment>, rustdoc::clean::clean_path::{closure#0}>>
            10: rustdoc::clean::clean_poly_trait_ref
            11: rustdoc::clean::clean_generic_bound
            12: <alloc::vec::Vec<rustdoc::clean::types::GenericBound> as alloc::vec::spec_from_iter::SpecFromIter<rustdoc::clean::types::GenericBound, core::iter::adapters::filter_map::FilterMap<core::slice::iter::Iter<rustc_hir::hir::GenericBound>, rustdoc::clean::clean_trait_item::{closure#0}::{closure#1}>>>::from_iter
            13: rustdoc::clean::clean_ty
            14: rustdoc::clean::utils::enter_impl_trait::<rustdoc::clean::clean_function::{closure#0}, (rustdoc::clean::types::Generics, rustdoc::clean::types::FnDecl)>
            15: rustdoc::clean::clean_fn_or_proc_macro
            16: <rustdoc::core::DocContext>::with_param_env::<alloc::vec::Vec<rustdoc::clean::types::Item>, rustdoc::clean::clean_maybe_renamed_item::{closure#1}>
            17: <&mut rustdoc::clean::clean_doc_module::{closure#2} as core::ops::function::FnOnce<(&(&rustc_hir::hir::Item, core::option::Option<rustc_span::symbol::Symbol>, core::option::Option<rustc_hir::hir_id::HirId>),)>>::call_once
            18: <alloc::vec::Vec<rustdoc::clean::types::Item> as alloc::vec::spec_extend::SpecExtend<rustdoc::clean::types::Item, core::iter::adapters::flatten::FlatMap<core::slice::iter::Iter<(&rustc_hir::hir::Item, core::option::Option<rustc_span::symbol::Symbol>, core::option::Option<rustc_hir::hir_id::HirId>)>, alloc::vec::Vec<rustdoc::clean::types::Item>, rustdoc::clean::clean_doc_module::{closure#2}>>>::spec_extend
            19: rustdoc::clean::clean_doc_module
            20: rustdoc::clean::utils::krate
            21: <rustc_session::session::Session>::time::<rustdoc::clean::types::Crate, rustdoc::core::run_global_ctxt::{closure#4}>
            22: rustdoc::core::run_global_ctxt
            23: <rustc_session::session::Session>::time::<(rustdoc::clean::types::Crate, rustdoc::config::RenderOptions, rustdoc::formats::cache::Cache), rustdoc::main_args::{closure#1}::{closure#0}::{closure#1}::{closure#0}>
            24: <rustc_interface::passes::QueryContext>::enter::<rustdoc::main_args::{closure#1}::{closure#0}::{closure#1}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            25: <rustc_interface::interface::Compiler>::enter::<rustdoc::main_args::{closure#1}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            26: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustdoc::main_args::{closure#1}>::{closure#0}::{closure#0}>
            27: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustdoc::main_args::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            28: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustdoc::main_args::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            29: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustdoc::main_args::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
            30: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/333ee6c466972185973d5097f8b5fb0f9fb13fa5/library/alloc/src/boxed.rs:1988:9
            31: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/333ee6c466972185973d5097f8b5fb0f9fb13fa5/library/alloc/src/boxed.rs:1988:9
            32: std::sys::unix::thread::Thread::new::thread_start
                       at /rustc/333ee6c466972185973d5097f8b5fb0f9fb13fa5/library/std/src/sys/unix/thread.rs:108:17
            33: <unknown>
            34: <unknown>


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 1.68.0-nightly (333ee6c46 2023-01-18) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack
thread panicked while panicking. aborting.
[2]    2838854 IOT instruction (core dumped)  rustdoc a.rs

Anything else?

No response

[compiler-errors]

Hm, this has to do with the fact that we don't check well-formedness during rustdoc, even though we really should at least be checking that the code in question has the right substs and stuff...

[megakorre]

So does rustdoc proceed with anything that can be parsed into HIR? cargo check rejects this with can't put a constant there.
What should the code do here in that case?.

• Make a dummy type and proceed with dock gen anyway.
• Actually run the type checking before generating docs.
• error without ICE and just print some general error message.
• Could also run the type check conditionality if something failed to type I guess and print the message from that.

[fmease]

This issue was fixed in #108576 but never closed. It now errors with:

error[E0747]: constant provided when a type was expected
 --> ice-107093.rs:3:28
  |
3 | fn gen() -> impl Generator<{}> {}
  |                            ^^

error: aborting due to previous error

I don't think that we need a regression test for this. The linked PR has added enough already.