thread 'rustc' panicked at 'assertion failed: promoted.is_none()', compiler/rustc_mir/src/transform/check_consts/qualifs.rs:250:9

[krinkinmu]

Hi,

I detected this problem by coincidence and reporting it just because the error message asked to do so.

Code

struct A<'a> {
    data: &'a [u32],
}

impl<'a> A<'a> {
    const fn new(data: &'a [u32]) -> A<'a> {
        A { data }
    }
}

pub fn setup() {
    static mut aa_storage: [A; 32] = [A::new(&[]); 32];
}

The problem goes away if I add #[derive(Clone, Copy)] to struct A, as required for the array initialization inside setup.

Meta

rustc --version --verbose:

rustc 1.50.0-nightly (bb1fbbf84 2020-12-22)
binary: rustc
commit-hash: bb1fbbf84455fbad9afd26c17e0f725019322655
commit-date: 2020-12-22
host: x86_64-unknown-linux-gnu
release: 1.50.0-nightly

I also verified that the problem exist after updating the toolchain in the version:

rustc 1.51.0-nightly (22ddcd1a1 2021-01-22)
binary: rustc
commit-hash: 22ddcd1a13082b7be0fc99b720677efd2b733816
commit-date: 2021-01-22
host: x86_64-unknown-linux-gnu
release: 1.51.0-nightly
LLVM version: 11.0.1

Error output

thread 'rustc' panicked at 'assertion failed: promoted.is_none()', compiler/rustc_mir/src/transform/check_consts/qualifs.rs:250:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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 1.51.0-nightly (22ddcd1a1 2021-01-22) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type rlib

query stack during panic:
#0 [mir_borrowck] borrow-checking `setup::aa_storage`
#1 [analysis] running analysis passes on this crate
end of query stack

Backtrace

thread 'rustc' panicked at 'assertion failed: promoted.is_none()', compiler/rustc_mir/src/transform/check_consts/qualifs.rs:250:9
stack backtrace:
   0: rust_begin_unwind
             at /rustc/22ddcd1a13082b7be0fc99b720677efd2b733816/library/std/src/panicking.rs:493:5
   1: core::panicking::panic_fmt
             at /rustc/22ddcd1a13082b7be0fc99b720677efd2b733816/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/22ddcd1a13082b7be0fc99b720677efd2b733816/library/core/src/panicking.rs:50:5
   3: rustc_mir::transform::check_consts::qualifs::in_operand
   4: rustc_mir::transform::promote_consts::Validator::qualif_local
   5: rustc_mir::transform::promote_consts::Validator::validate_local
   6: rustc_mir::transform::promote_consts::Validator::validate_place
   7: rustc_mir::transform::promote_consts::Validator::validate_local
   8: rustc_mir::transform::promote_consts::Validator::validate_place
   9: rustc_mir::transform::promote_consts::Validator::validate_local
  10: rustc_mir::transform::promote_consts::Validator::validate_place
  11: rustc_mir::transform::promote_consts::Validator::validate_local
  12: rustc_mir::transform::promote_consts::Validator::validate_place
  13: rustc_mir::transform::promote_consts::should_suggest_const_in_array_repeat_expressions_attribute
  14: rustc_mir::borrow_check::type_check::TypeChecker::check_rvalue
  15: rustc_mir::borrow_check::type_check::TypeChecker::typeck_mir
  16: rustc_mir::borrow_check::type_check::type_check
  17: rustc_mir::borrow_check::nll::compute_regions
  18: rustc_mir::borrow_check::do_mir_borrowck
  19: rustc_infer::infer::InferCtxtBuilder::enter
  20: rustc_mir::borrow_check::mir_borrowck
  21: core::ops::function::FnOnce::call_once
  22: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_borrowck>::compute
  23: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  24: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  25: rustc_query_system::query::plumbing::force_query_with_job
  26: rustc_query_system::query::plumbing::get_query_impl
  27: rustc_query_system::query::plumbing::ensure_query_impl
  28: rustc_session::utils::<impl rustc_session::session::Session>::time
  29: rustc_interface::passes::analysis
  30: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  31: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  32: rustc_data_structures::stack::ensure_sufficient_stack
  33: rustc_query_system::query::plumbing::force_query_with_job
  34: rustc_query_system::query::plumbing::get_query_impl
  35: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  36: rustc_span::with_source_map
  37: rustc_interface::interface::create_compiler_and_run
  38: rustc_span::with_session_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[camelid]

This ICE first appeared in 1.42, but this code first started ICEing (with a slightly different message) in 1.41.

@rustbot label: regression-from-stable-to-stable

[camelid]

Minimized:

struct A {
    data: &'static u32,
}

const aa_storage: [A; 32] = [A { data: &1 }; 32];

(Playground)

Errors:

   Compiling playground v0.0.1 (/playground)
thread 'rustc' panicked at 'assertion failed: promoted.is_none()', compiler/rustc_mir/src/transform/check_consts/qualifs.rs:250:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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 1.51.0-nightly (4d0dd02ee 2021-01-23) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 --crate-type lib

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `aa_storage`
#1 [analysis] running analysis passes on this crate
end of query stack
error: could not compile `playground`

To learn more, run the command again with --verbose.

Doesn't require const fn:
@rustbot label: -A-const-fn

This code also doesn't use nightly features.

[apiraino]

Assigning P-high as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.