ICE: `Got a scalar pair where a scalar was expected`

[Naserume]

Code

trait Qux {
    fn bar() -> i32;
}

pub struct Lint {
    pub desc: &'static Qux,
}

static FOO: &Lint = &Lint { desc: "desc" };

fn main() {}

Meta

rustc --version --verbose:

rustc 1.81.0-nightly (6292b2af6 2024-07-02)
binary: rustc
commit-hash: 6292b2af620dbd771ebb687c3a93c69ba8f97268
commit-date: 2024-07-02
host: x86_64-apple-darwin
release: 1.81.0-nightly
LLVM version: 18.1.7

Error output

warning: trait objects without an explicit `dyn` are deprecated
  --> ./7F1DF.rs:13:24
   |
13 |     pub desc: &'static Qux,
   |                        ^^^
   |
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
   = note: `#[warn(bare_trait_objects)]` on by default
help: if this is an object-safe trait, use `dyn`
   |
13 |     pub desc: &'static dyn Qux,
   |                        +++

error[E0038]: the trait `Qux` cannot be made into an object
  --> ./7F1DF.rs:13:24
   |
13 |     pub desc: &'static Qux,
   |                        ^^^ `Qux` cannot be made into an object
   |
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
  --> ./7F1DF.rs:2:8
   |
1  | trait Qux {
   |       --- this trait cannot be made into an object...
2  |     fn bar() -> i32;
   |        ^^^ ...because associated function `bar` has no `self` parameter
help: consider turning `bar` into a method by giving it a `&self` argument
   |
2  |     fn bar(&self) -> i32;
   |            +++++
help: alternatively, consider constraining `bar` so it does not apply to trait objects
   |
2  |     fn bar() -> i32 where Self: Sized;
   |                     +++++++++++++++++

error[E0277]: `(dyn Qux + 'static)` cannot be shared between threads safely
  --> ./7F1DF.rs:16:13
   |
16 | static FOO: &Lint = &Lint { desc: "desc" };
   |             ^^^^^ `(dyn Qux + 'static)` cannot be shared between threads safely
   |
   = help: within `&'static Lint`, the trait `Sync` is not implemented for `(dyn Qux + 'static)`, which is required by `&'static Lint: Sync`
   = note: required because it appears within the type `&'static (dyn Qux + 'static)`
note: required because it appears within the type `Lint`
  --> ./7F1DF.rs:12:12
   |
12 | pub struct Lint {
   |            ^^^^
   = note: required because it appears within the type `&'static Lint`
   = note: shared static variables must have a type that implements `Sync`

error[E0038]: the trait `Qux` cannot be made into an object
  --> ./7F1DF.rs:16:35
   |
16 | static FOO: &Lint = &Lint { desc: "desc" };
   |                                   ^^^^^^ `Qux` cannot be made into an object
   |
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
  --> ./7F1DF.rs:2:8
   |
1  | trait Qux {
   |       --- this trait cannot be made into an object...
2  |     fn bar() -> i32;
   |        ^^^ ...because associated function `bar` has no `self` parameter
   = note: required for the cast from `&'static str` to `&'static (dyn Qux + 'static)`
help: consider turning `bar` into a method by giving it a `&self` argument
   |
2  |     fn bar(&self) -> i32;
   |            +++++
help: alternatively, consider constraining `bar` so it does not apply to trait objects
   |
2  |     fn bar() -> i32 where Self: Sized;
   |                     +++++++++++++++++

Backtrace

error: internal compiler error: compiler/rustc_const_eval/src/interpret/operand.rs:85:42: Got a scalar pair where a scalar was expected

thread 'rustc' panicked at compiler/rustc_const_eval/src/interpret/operand.rs:85:42:
Box<dyn Any>
stack backtrace:
   0:        0x1029f2d93 - <std::sys::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h9393e218f71d31cf
   1:        0x102a3e17b - core::fmt::write::h1271a75a7bae980c
   2:        0x1029e8c3e - std::io::Write::write_fmt::h8270e961acbabe61
   3:        0x1029f2b81 - std::sys::backtrace::print::h04e4916ebe343f6e
   4:        0x1029f5959 - std::panicking::default_hook::{{closure}}::hc9df26d29e0f9e5a
   5:        0x1029f56da - std::panicking::default_hook::h1026261fa8b9d0a8
   6:        0x10bcdd0ac - std[26270defc80edaa9]::panicking::update_hook::<alloc[98df03226deedbda]::boxed::Box<rustc_driver_impl[708b2ec565622c48]::install_ice_hook::{closure#0}>>::{closure#0}
   7:        0x1029f6699 - std::panicking::rust_panic_with_hook::hf72d729757d375cc
   8:        0x10bd51347 - std[26270defc80edaa9]::panicking::begin_panic::<rustc_errors[d689bc684dcf46ea]::ExplicitBug>::{closure#0}
   9:        0x10bd3d189 - std[26270defc80edaa9]::sys::backtrace::__rust_end_short_backtrace::<std[26270defc80edaa9]::panicking::begin_panic<rustc_errors[d689bc684dcf46ea]::ExplicitBug>::{closure#0}, !>
  10:        0x11076e199 - std[26270defc80edaa9]::panicking::begin_panic::<rustc_errors[d689bc684dcf46ea]::ExplicitBug>
  11:        0x10bd63486 - <rustc_errors[d689bc684dcf46ea]::diagnostic::BugAbort as rustc_errors[d689bc684dcf46ea]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:        0x10ca066a5 - rustc_middle[8094f41c293b336b]::util::bug::opt_span_bug_fmt::<rustc_span[2de937bbddea0bd8]::span_encoding::Span>::{closure#0}
  13:        0x10c9bd967 - rustc_middle[8094f41c293b336b]::ty::context::tls::with_opt::<rustc_middle[8094f41c293b336b]::util::bug::opt_span_bug_fmt<rustc_span[2de937bbddea0bd8]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:        0x10c9bd405 - rustc_middle[8094f41c293b336b]::ty::context::tls::with_context_opt::<rustc_middle[8094f41c293b336b]::ty::context::tls::with_opt<rustc_middle[8094f41c293b336b]::util::bug::opt_span_bug_fmt<rustc_span[2de937bbddea0bd8]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:        0x1108311cb - rustc_middle[8094f41c293b336b]::util::bug::bug_fmt
  16:        0x10bc36d21 - <rustc_const_eval[396cbee6e07433a6]::interpret::eval_context::InterpCx<rustc_const_eval[396cbee6e07433a6]::const_eval::machine::CompileTimeMachine>>::read_scalar::<rustc_const_eval[396cbee6e07433a6]::interpret::operand::OpTy>
  17:        0x10bc36d50 - <rustc_const_eval[396cbee6e07433a6]::interpret::eval_context::InterpCx<rustc_const_eval[396cbee6e07433a6]::const_eval::machine::CompileTimeMachine>>::read_pointer::<rustc_const_eval[396cbee6e07433a6]::interpret::operand::OpTy>
  18:        0x10bc1b9de - <rustc_const_eval[396cbee6e07433a6]::interpret::eval_context::InterpCx<rustc_const_eval[396cbee6e07433a6]::const_eval::machine::CompileTimeMachine>>::unsize_into_ptr
  19:        0x10bc4612c - <rustc_const_eval[396cbee6e07433a6]::interpret::eval_context::InterpCx<rustc_const_eval[396cbee6e07433a6]::const_eval::machine::CompileTimeMachine>>::statement
  20:        0x10bc62ed8 - rustc_const_eval[396cbee6e07433a6]::const_eval::eval_queries::eval_to_allocation_raw_provider
  21:        0x10d39aaec - rustc_query_impl[36fa5edae9172c7f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_to_allocation_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 24usize]>>
  22:        0x10d34fbae - <rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_to_allocation_raw::dynamic_query::{closure#2} as core[c342ec502b95801]::ops::function::FnOnce<(rustc_middle[8094f41c293b336b]::ty::context::TyCtxt, rustc_middle[8094f41c293b336b]::ty::ParamEnvAnd<rustc_middle[8094f41c293b336b]::mir::interpret::GlobalId>)>>::call_once
  23:        0x10d1b3c0d - rustc_query_system[16c7cab3586fd5d4]::query::plumbing::try_execute_query::<rustc_query_impl[36fa5edae9172c7f]::DynamicConfig<rustc_query_system[16c7cab3586fd5d4]::query::caches::DefaultCache<rustc_middle[8094f41c293b336b]::ty::ParamEnvAnd<rustc_middle[8094f41c293b336b]::mir::interpret::GlobalId>, rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[36fa5edae9172c7f]::plumbing::QueryCtxt, false>
  24:        0x10d3c59dc - rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_to_allocation_raw::get_query_non_incr::__rust_end_short_backtrace
  25:        0x10bb93752 - rustc_middle[8094f41c293b336b]::query::plumbing::query_get_at::<rustc_query_system[16c7cab3586fd5d4]::query::caches::DefaultCache<rustc_middle[8094f41c293b336b]::ty::ParamEnvAnd<rustc_middle[8094f41c293b336b]::mir::interpret::GlobalId>, rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 24usize]>>>
  26:        0x10bc5f700 - rustc_const_eval[396cbee6e07433a6]::const_eval::eval_queries::eval_to_const_value_raw_provider
  27:        0x10d39b48c - rustc_query_impl[36fa5edae9172c7f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_to_const_value_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 24usize]>>
  28:        0x10d35501e - <rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_to_const_value_raw::dynamic_query::{closure#2} as core[c342ec502b95801]::ops::function::FnOnce<(rustc_middle[8094f41c293b336b]::ty::context::TyCtxt, rustc_middle[8094f41c293b336b]::ty::ParamEnvAnd<rustc_middle[8094f41c293b336b]::mir::interpret::GlobalId>)>>::call_once
  29:        0x10d1b3c0d - rustc_query_system[16c7cab3586fd5d4]::query::plumbing::try_execute_query::<rustc_query_impl[36fa5edae9172c7f]::DynamicConfig<rustc_query_system[16c7cab3586fd5d4]::query::caches::DefaultCache<rustc_middle[8094f41c293b336b]::ty::ParamEnvAnd<rustc_middle[8094f41c293b336b]::mir::interpret::GlobalId>, rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[36fa5edae9172c7f]::plumbing::QueryCtxt, false>
  30:        0x10d3c628c - rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_to_const_value_raw::get_query_non_incr::__rust_end_short_backtrace
  31:        0x10ca1df16 - rustc_middle[8094f41c293b336b]::query::plumbing::query_get_at::<rustc_query_system[16c7cab3586fd5d4]::query::caches::DefaultCache<rustc_middle[8094f41c293b336b]::ty::ParamEnvAnd<rustc_middle[8094f41c293b336b]::mir::interpret::GlobalId>, rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 24usize]>>>
  32:        0x10ca220ce - <rustc_middle[8094f41c293b336b]::ty::context::TyCtxt>::const_eval_global_id
  33:        0x10ca219ed - <rustc_middle[8094f41c293b336b]::ty::context::TyCtxt>::const_eval_resolve
  34:        0x10bc389bb - <rustc_const_eval[396cbee6e07433a6]::interpret::eval_context::InterpCx<rustc_const_eval[396cbee6e07433a6]::const_eval::machine::CompileTimeMachine>>::eval_operand
  35:        0x10bc451b6 - <rustc_const_eval[396cbee6e07433a6]::interpret::eval_context::InterpCx<rustc_const_eval[396cbee6e07433a6]::const_eval::machine::CompileTimeMachine>>::statement
  36:        0x10bc6189b - rustc_const_eval[396cbee6e07433a6]::const_eval::eval_queries::eval_static_initializer_provider
  37:        0x10d39b412 - rustc_query_impl[36fa5edae9172c7f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_static_initializer::dynamic_query::{closure#2}::{closure#0}, rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 16usize]>>
  38:        0x10d35459e - <rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_static_initializer::dynamic_query::{closure#2} as core[c342ec502b95801]::ops::function::FnOnce<(rustc_middle[8094f41c293b336b]::ty::context::TyCtxt, rustc_span[2de937bbddea0bd8]::def_id::DefId)>>::call_once
  39:        0x10d158319 - rustc_query_system[16c7cab3586fd5d4]::query::plumbing::try_execute_query::<rustc_query_impl[36fa5edae9172c7f]::DynamicConfig<rustc_query_system[16c7cab3586fd5d4]::query::caches::DefIdCache<rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[36fa5edae9172c7f]::plumbing::QueryCtxt, false>
  40:        0x10d3c5ded - rustc_query_impl[36fa5edae9172c7f]::query_impl::eval_static_initializer::get_query_non_incr::__rust_end_short_backtrace
  41:        0x10bf56cbb - <rustc_middle[8094f41c293b336b]::hir::map::Map>::par_body_owners::<rustc_hir_analysis[af0a509199b1bc4b]::check_crate::{closure#3}>::{closure#0}
  42:        0x10c0ac0ec - rustc_hir_analysis[af0a509199b1bc4b]::check_crate
  43:        0x10c653df7 - rustc_interface[eab3c32d3b591e25]::passes::run_required_analyses
  44:        0x10c6563a0 - rustc_interface[eab3c32d3b591e25]::passes::analysis
  45:        0x10d39d4ec - rustc_query_impl[36fa5edae9172c7f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[36fa5edae9172c7f]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 1usize]>>
  46:        0x10d17bfbe - rustc_query_system[16c7cab3586fd5d4]::query::plumbing::try_execute_query::<rustc_query_impl[36fa5edae9172c7f]::DynamicConfig<rustc_query_system[16c7cab3586fd5d4]::query::caches::SingleCache<rustc_middle[8094f41c293b336b]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[36fa5edae9172c7f]::plumbing::QueryCtxt, false>
  47:        0x10d3a7a47 - rustc_query_impl[36fa5edae9172c7f]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  48:        0x10bc86857 - <rustc_interface[eab3c32d3b591e25]::queries::QueryResult<&rustc_middle[8094f41c293b336b]::ty::context::GlobalCtxt>>::enter::<core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>, rustc_driver_impl[708b2ec565622c48]::run_compiler::{closure#0}::{closure#1}::{closure#5}>
  49:        0x10bce4465 - rustc_interface[eab3c32d3b591e25]::interface::run_compiler::<core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>, rustc_driver_impl[708b2ec565622c48]::run_compiler::{closure#0}>::{closure#1}
  50:        0x10bccaee1 - std[26270defc80edaa9]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[eab3c32d3b591e25]::util::run_in_thread_with_globals<rustc_interface[eab3c32d3b591e25]::util::run_in_thread_pool_with_globals<rustc_interface[eab3c32d3b591e25]::interface::run_compiler<core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>, rustc_driver_impl[708b2ec565622c48]::run_compiler::{closure#0}>::{closure#1}, core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>>::{closure#0}, core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>>
  51:        0x10bceaff6 - <<std[26270defc80edaa9]::thread::Builder>::spawn_unchecked_<rustc_interface[eab3c32d3b591e25]::util::run_in_thread_with_globals<rustc_interface[eab3c32d3b591e25]::util::run_in_thread_pool_with_globals<rustc_interface[eab3c32d3b591e25]::interface::run_compiler<core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>, rustc_driver_impl[708b2ec565622c48]::run_compiler::{closure#0}>::{closure#1}, core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>>::{closure#0}, core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[c342ec502b95801]::result::Result<(), rustc_span[2de937bbddea0bd8]::ErrorGuaranteed>>::{closure#2} as core[c342ec502b95801]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  52:        0x1029ff83b - std::sys::pal::unix::thread::Thread::new::thread_start::hfcd29f6cc9954faa
  53:     0x7ff801f5318b - __pthread_start

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: please make sure that you have updated to the latest nightly

note: please attach the file at `/Users/240701-nightly/rustc-ice-2024-07-04T05_30_36-80768.txt` to your bug report

query stack during panic:
#0 [eval_to_allocation_raw] const-evaluating + checking `FOO::promoted[0]`
#1 [eval_to_const_value_raw] simplifying constant for the type system `FOO::promoted[0]`
end of query stack
error: aborting due to 4 previous errors; 1 warning emitted

Some errors have detailed explanations: E0038, E0277.
For more information about an error, try `rustc --explain E0038`.

Note

Ice location

rust/compiler/rustc_const_eval/src/interpret/operand.rs

Lines 80 to 88 in 6292b2a

	#[inline]
	#[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
	pub fn to_scalar(self) -> Scalar<Prov> {
	match self {
	Immediate::Scalar(val) => val,
	Immediate::ScalarPair(..) => bug!("Got a scalar pair where a scalar was expected"),
	Immediate::Uninit => bug!("Got uninit where a scalar was expected"),
	}
	}

[GrigorenkoPV]

searched nightlies: from nightly-2023-04-15 to nightly-2024-07-02
regressed nightly: nightly-2024-07-02
searched commit range: 6868c83...cf2df68
regressed commit: 7b21c18 (#126996, cc @oli-obk)