ICE: #[rustc_variance] on trait: asked to compute variance for wrong kind of item

[matthiaskrgr]

Code

#![feature(rustc_attrs)]

#[rustc_variance]
trait Tr { }

fn main() { }

Meta

rustc --version --verbose:

rustc 1.50.0-nightly (e9dd18ca7 2020-12-04)
binary: rustc
commit-hash: e9dd18ca749801a19d85bfb424ae12011a8ff894
commit-date: 2020-12-04
host: x86_64-unknown-linux-gnu
release: 1.50.0-nightly

Error output

error: internal compiler error: compiler/rustc_typeck/src/variance/mod.rs:45:9: asked to compute variance for wrong kind of item
 --> ./src/test/compile-fail/variance-region-bounds.rs:4:1
  |
4 | trait Tr { }
  | ^^^^^^^^^^^^

thread 'rustc' panicked at 'Box<Any>', /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/compiler/rustc_errors/src/lib.rs:904:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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 1.50.0-nightly (e9dd18ca7 2020-12-04) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [variances_of] computing the variances of `Tr`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

Backtrace

error: internal compiler error: compiler/rustc_typeck/src/variance/mod.rs:45:9: asked to compute variance for wrong kind of item
 --> ./src/test/compile-fail/variance-region-bounds.rs:4:1
  |
4 | trait Tr { }
  | ^^^^^^^^^^^^

thread 'rustc' panicked at 'Box<Any>', /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/compiler/rustc_errors/src/lib.rs:904:9
stack backtrace:
   0:     0x7f90f0b2b990 - std::backtrace_rs::backtrace::libunwind::trace::h746c3e9529d524bc
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x7f90f0b2b990 - std::backtrace_rs::backtrace::trace_unsynchronized::h86340908ff889faa
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f90f0b2b990 - std::sys_common::backtrace::_print_fmt::h43f85f9b18230404
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f90f0b2b990 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hc132ae1a5b5aa7cd
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7f90f0b9f58c - core::fmt::write::hdf023a0036d2a25f
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/core/src/fmt/mod.rs:1078:17
   5:     0x7f90f0b1d462 - std::io::Write::write_fmt::h8580846154bcb66a
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/io/mod.rs:1519:15
   6:     0x7f90f0b2f615 - std::sys_common::backtrace::_print::h7ee55fed88d107a3
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7f90f0b2f615 - std::sys_common::backtrace::print::h54a7d3e52a524177
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7f90f0b2f615 - std::panicking::default_hook::{{closure}}::h60921e857bf55a40
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/panicking.rs:208:50
   9:     0x7f90f0b2f16a - std::panicking::default_hook::hf0f9afb1017317fc
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/panicking.rs:225:9
  10:     0x7f90f13c4948 - rustc_driver::report_ice::hff78d76a39ffbb86
  11:     0x7f90f0b2ff16 - std::panicking::rust_panic_with_hook::h8d66bf42b407aaea
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/panicking.rs:595:17
  12:     0x7f90f205ec3d - std::panicking::begin_panic::{{closure}}::h54eeb46bac46db82
  13:     0x7f90f205eb86 - std::sys_common::backtrace::__rust_end_short_backtrace::h4e2b24765319763c
  14:     0x7f90f1f40f1f - std::panicking::begin_panic::hc2016e83d046c641
  15:     0x7f90f204441c - rustc_errors::HandlerInner::span_bug::h8e6533b92ab43aa3
  16:     0x7f90f20446d0 - rustc_errors::Handler::span_bug::h572b00fe05637c58
  17:     0x7f90f211e554 - rustc_middle::util::bug::opt_span_bug_fmt::{{closure}}::h5cb28236637f8e39
  18:     0x7f90f211e14b - rustc_middle::ty::context::tls::with_opt::{{closure}}::h4b587d06910badc4
  19:     0x7f90f211e0f2 - rustc_middle::ty::context::tls::with_opt::h1de5816033aded9d
  20:     0x7f90f211e453 - rustc_middle::util::bug::opt_span_bug_fmt::hfae2ed8f53b5e93e
  21:     0x7f90f211e417 - rustc_middle::util::bug::span_bug_fmt::h5fd16dadd4aa27be
  22:     0x7f90f20775e7 - rustc_typeck::variance::variances_of::{{closure}}::h20f743f215738ce1
  23:     0x7f90f207739a - rustc_typeck::variance::variances_of::h57ac03785ddd37d0
  24:     0x7f90f1f302f2 - rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::variances_of>::compute::h29ccb15266121033
  25:     0x7f90f200c065 - rustc_query_system::dep_graph::graph::DepGraph<K>::with_task::h45e1bc6044779c4d
  26:     0x7f90f202beb4 - rustc_data_structures::stack::ensure_sufficient_stack::he988aaa7327e6398
  27:     0x7f90f21a71f4 - rustc_query_system::query::plumbing::get_query_impl::hbcf2f924d8608ce6
  28:     0x7f90f1f57fb3 - <rustc_typeck::variance::test::VarianceTest as rustc_hir::itemlikevisit::ItemLikeVisitor>::visit_item::he7d71188a6857160
  29:     0x7f90f209b646 - rustc_hir::hir::Crate::visit_all_item_likes::hea439839e1e6c838
  30:     0x7f90f2078a91 - rustc_typeck::check_crate::hab874d5f99f602e6
  31:     0x7f90f1624642 - rustc_interface::passes::analysis::h34f9b972d8af6f3d
  32:     0x7f90f1380f7b - rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute::h95ff81a8a73eaff3
  33:     0x7f90f140f486 - rustc_query_system::dep_graph::graph::DepGraph<K>::with_eval_always_task::h05a5aa3f40ff3b2d
  34:     0x7f90f1422686 - rustc_data_structures::stack::ensure_sufficient_stack::h371083fbc17898bc
  35:     0x7f90f13aecb4 - rustc_query_system::query::plumbing::get_query_impl::hcc63ca689fa3c69b
  36:     0x7f90f138321b - rustc_interface::passes::QueryContext::enter::h2071e0a8631ee0e4
  37:     0x7f90f1420045 - rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter::hd899306a06575d0c
  38:     0x7f90f13eddf7 - rustc_span::with_source_map::ha4e07ff263d0dc1d
  39:     0x7f90f141bdec - scoped_tls::ScopedKey<T>::set::h39c0aa543118d3f3
  40:     0x7f90f1423296 - std::sys_common::backtrace::__rust_begin_short_backtrace::h1e5aa72fb9cd6d86
  41:     0x7f90f138afca - core::ops::function::FnOnce::call_once{{vtable.shim}}::hc793837e985b77ce
  42:     0x7f90f0b3f99a - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hea1090dbdcecbf5a
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/alloc/src/boxed.rs:1327:9
  43:     0x7f90f0b3f99a - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h8d5723d3912bd325
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/alloc/src/boxed.rs:1327:9
  44:     0x7f90f0b3f99a - std::sys::unix::thread::Thread::new::thread_start::hc17a425ca2995724
                               at /rustc/e9dd18ca749801a19d85bfb424ae12011a8ff894/library/std/src/sys/unix/thread.rs:71:17
  45:     0x7f90f0a353e9 - start_thread
  46:     0x7f90f0952293 - __GI___clone
  47:                0x0 - <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 1.50.0-nightly (e9dd18ca7 2020-12-04) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [variances_of] computing the variances of `Tr`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

[matthiaskrgr]

The ICE happens on stable as well, for some reason.
( I do get a '#![feature]' may not be used on the stable release channel warning though)
Versions as early as 1.44 crash, I didn't dig any further.

[matthiaskrgr]

@rustbot modify labels to +regression-from-stable-to-stable

[camelid]

@rustbot glacier "https://gist.github.com/rust-play/b841b10d5b257ef0bb1c72e8ce722c6e"

[camelid]

@Stupremee Why did you remove requires-nightly? I know that the ICE occurs on stable, but you need the feature flag (and thus nightly) to actually use it.

[camelid]

Assigning P-medium and removing I-prioritize as discussed in the prioritization working group.

[Stupremee]

@Stupremee Why did you remove requires-nightly? I know that the ICE occurs on stable, but you need the feature flag (and thus nightly) to actually use it.

To reproduce the ICE you don't need nightly and thus I thought it's wrong. Correct me if I'm misunderstanding the requires-nightly label

[camelid]

TMK, we use requires-nightly if it requires a nightly feature. I guess what I'm saying is: you can produce on stable, but it doesn't affect stable code because to actually use the code you need to be on nightly. But I think it's fine to be more cautious in this case and not use requires-nightly. So it's fine :)

[chengniansun]

A duplicate.

#![feature(rustc_attrs)]
#[rustc_variance]
impl Words {}

[smmalis37]

Bisected:

---

Regression in nightly-2018-09-10

---

found 8 bors merge commits in the specified range
commit[0] 2018-09-08UTC: Auto merge of #53909 - mikhail-m1:53643, r=nikomatsakis
commit[1] 2018-09-09UTC: Auto merge of #53949 - estebank:unclosed-delim, r=nikomatsakis
commit[2] 2018-09-09UTC: Auto merge of #53960 - estebank:issue-51303, r=nagisa
commit[3] 2018-09-09UTC: Auto merge of #53988 - eddyb:issue-53770, r=petrochenkov
commit[4] 2018-09-09UTC: Auto merge of #53998 - eddyb:issue-53728, r=oli-obk
commit[5] 2018-09-09UTC: Auto merge of #53902 - dtolnay:group, r=petrochenkov
commit[6] 2018-09-09UTC: Auto merge of #54057 - matthiaskrgr:stabilize-edition-plus-clippy, r=Mark-Simulacrum
commit[7] 2018-09-09UTC: Auto merge of #53778 - petrochenkov:shadrelax2, r=nikomatsakis
ERROR: no commits between 0198a1e and 2d4e34c within last 167 days

[chengniansun]

Another duplicate.

#![feature(rustc_attrs)]
#[rustc_variance]
const GOO: Cake;

[cjgillot]

rustc_variance is a rustc internal debugging tool. Closing as WONTFIX.