ICE: 'tls access is checked in `Rvalue::ThreadLocalRef', compiler/rustc_mir/src/transform/check_consts/validation.rs:359:9

[chengniansun]

Code

#![feature(thread_local)]
#[thread_local]
static mut STATIC_VAR_2: [u32; 8] = [4; 8];
const fn g(x: &mut [u32; 8]) {
    std::mem::swap(x, &mut STATIC_VAR_2)
}

Meta

rustc --version --verbose:

rustc 1.54.0-nightly (9111b8ae9 2021-05-26)
binary: rustc
commit-hash: 9111b8ae9793f18179a1336417618fc07a9cac85
commit-date: 2021-05-26
host: x86_64-unknown-linux-gnu
release: 1.54.0-nightly
LLVM version: 12.0.1

Error output

error[E0658]: mutable references are not allowed in constant functions
 --> mutant.rs:4:12
  |
4 | const fn g(x: &mut [u32; 8]) {
  |            ^
  |
  = note: see issue #57349 <https://github.com/rust-lang/rust/issues/57349> for more information
  = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable

error[E0625]: thread-local statics cannot be accessed at compile-time
 --> mutant.rs:5:28
  |
5 |     std::mem::swap(x, &mut STATIC_VAR_2)
  |                            ^^^^^^^^^^^^

thread 'rustc' panicked at 'tls access is checked in `Rvalue::ThreadLocalRef', compiler/rustc_mir/src/transform/check_consts/validation.rs:359:9
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 1.54.0-nightly (9111b8ae9 2021-05-26) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type staticlib

query stack during panic:
#0 [mir_const_qualif] const checking `g`
#1 [mir_promoted] processing `g`
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.

Backtrace

error[E0658]: mutable references are not allowed in constant functions
 --> mutant.rs:4:12
  |
4 | const fn g(x: &mut [u32; 8]) {
  |            ^
  |
  = note: see issue #57349 <https://github.com/rust-lang/rust/issues/57349> for more information
  = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable

error[E0625]: thread-local statics cannot be accessed at compile-time
 --> mutant.rs:5:28
  |
5 |     std::mem::swap(x, &mut STATIC_VAR_2)
  |                            ^^^^^^^^^^^^

thread 'rustc' panicked at 'tls access is checked in `Rvalue::ThreadLocalRef', compiler/rustc_mir/src/transform/check_consts/validation.rs:359:9
stack backtrace:
   0: std::panicking::begin_panic
   1: rustc_mir::transform::check_consts::validation::Validator::check_static
   2: <rustc_mir::transform::check_consts::validation::Validator as rustc_middle::mir::visit::Visitor>::visit_rvalue
   3: <rustc_mir::transform::check_consts::validation::Validator as rustc_middle::mir::visit::Visitor>::visit_statement
   4: rustc_mir::transform::check_consts::validation::Validator::check_body
   5: rustc_mir::transform::mir_const_qualif
   6: core::ops::function::FnOnce::call_once
   7: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
   8: rustc_data_structures::stack::ensure_sufficient_stack
   9: rustc_query_system::query::plumbing::force_query_with_job
  10: rustc_query_system::query::plumbing::get_query_impl
  11: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_const_qualif
  12: rustc_mir::transform::mir_promoted
  13: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  14: rustc_data_structures::stack::ensure_sufficient_stack
  15: rustc_query_system::query::plumbing::force_query_with_job
  16: rustc_query_system::query::plumbing::get_query_impl
  17: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_promoted
  18: rustc_mir::borrow_check::mir_borrowck
  19: core::ops::function::FnOnce::call_once
  20: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  21: rustc_data_structures::stack::ensure_sufficient_stack
  22: rustc_query_system::query::plumbing::force_query_with_job
  23: rustc_query_system::query::plumbing::get_query_impl
  24: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_borrowck
  25: rustc_middle::ty::<impl rustc_middle::ty::context::TyCtxt>::par_body_owners
  26: rustc_interface::passes::analysis
  27: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  28: rustc_data_structures::stack::ensure_sufficient_stack
  29: rustc_query_system::query::plumbing::force_query_with_job
  30: rustc_query_system::query::plumbing::get_query_impl
  31: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
  32: rustc_interface::passes::QueryContext::enter
  33: rustc_span::with_session_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose 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 1.54.0-nightly (9111b8ae9 2021-05-26) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type staticlib

query stack during panic:
#0 [mir_const_qualif] const checking `g`
#1 [mir_promoted] processing `g`
#2 [mir_borrowck] borrow-checking `g`
#3 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.

[LingMan]

The failing assert is:

rust/compiler/rustc_mir/src/transform/check_consts/validation.rs

Lines 359 to 362 in f77b1a5

	assert!(
	!self.tcx.is_thread_local_static(def_id),
	"tls access is checked in `Rvalue::ThreadLocalRef"
	);

Trying to bisect leads me all the way back to 2020-06-02, but that's just the day the assert was added in the first place (#71192). Had to add #![feature(const_fn)] somewhere in late September 2020 though.