ICE: `invalid field type in Immediate::offset: value Scalar(0x0000000000000000) does not match ABI ScalarPair(..)`

[matthiaskrgr]

snippet:

//@compile-flags: -Zmir-enable-passes=+Inline -Zmir-enable-passes=+JumpThreading --crate-type=lib
pub fn problem_thingy(items: &mut impl Iterator<Item = str>) {
    let mut peeker = items.peekable();
    match peeker.peek() {
        Some(_) => (),
        None => return (),
    }
}

Version information

rustc 1.86.0-nightly (6dd75f0d6 2025-02-02)
binary: rustc
commit-hash: 6dd75f0d6802f56564f5f9c947a85ded286d3986
commit-date: 2025-02-02
host: x86_64-unknown-linux-gnu
release: 1.86.0-nightly
LLVM version: 19.1.7

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zmir-enable-passes=+Inline -Zmir-enable-passes=+JumpThreading --crate-type=lib

Program output

error: internal compiler error: /rustc/6dd75f0d6802f56564f5f9c947a85ded286d3986/compiler/rustc_const_eval/src/interpret/operand.rs:157:17: invalid field type in Immediate::offset: value Scalar(0x0000000000000000) does not match ABI ScalarPair(Initialized { value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }, Initialized { value: Int(I64, false), valid_range: 0..=18446744073709551615 }))


thread 'rustc' panicked at /rustc/6dd75f0d6802f56564f5f9c947a85ded286d3986/compiler/rustc_const_eval/src/interpret/operand.rs:157:17:
Box<dyn Any>
stack backtrace:
   0:     0x74a71602ed50 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hbfd757a12de5328f
   1:     0x74a716814826 - core::fmt::write::h8a36a2b16afbec2c
   2:     0x74a717b39a51 - std::io::Write::write_fmt::h405e3b74afe27f82
   3:     0x74a71602ebb2 - std::sys::backtrace::BacktraceLock::print::h83c9aa10f541661c
   4:     0x74a716031032 - std::panicking::default_hook::{{closure}}::h720ed0d152826500
   5:     0x74a716030eba - std::panicking::default_hook::hfc73f50ca652e2b3
   6:     0x74a715189389 - std[ff511cecd2b9d7cf]::panicking::update_hook::<alloc[c4f21c44eb49384f]::boxed::Box<rustc_driver_impl[b88f56deeb7372ac]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x74a716031bb3 - std::panicking::rust_panic_with_hook::h73e8d76e64e48546
   8:     0x74a7151c4051 - std[ff511cecd2b9d7cf]::panicking::begin_panic::<rustc_errors[bb44e506870335f6]::ExplicitBug>::{closure#0}
   9:     0x74a7151b8fc6 - std[ff511cecd2b9d7cf]::sys::backtrace::__rust_end_short_backtrace::<std[ff511cecd2b9d7cf]::panicking::begin_panic<rustc_errors[bb44e506870335f6]::ExplicitBug>::{closure#0}, !>
  10:     0x74a7151b8fad - std[ff511cecd2b9d7cf]::panicking::begin_panic::<rustc_errors[bb44e506870335f6]::ExplicitBug>
  11:     0x74a7151cdfa1 - <rustc_errors[bb44e506870335f6]::diagnostic::BugAbort as rustc_errors[bb44e506870335f6]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x74a7157b3bf3 - rustc_middle[f2fffebf67d4dac6]::util::bug::opt_span_bug_fmt::<rustc_span[4bd220f521370a86]::span_encoding::Span>::{closure#0}
  13:     0x74a71579cb7a - rustc_middle[f2fffebf67d4dac6]::ty::context::tls::with_opt::<rustc_middle[f2fffebf67d4dac6]::util::bug::opt_span_bug_fmt<rustc_span[4bd220f521370a86]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x74a71579ca0b - rustc_middle[f2fffebf67d4dac6]::ty::context::tls::with_context_opt::<rustc_middle[f2fffebf67d4dac6]::ty::context::tls::with_opt<rustc_middle[f2fffebf67d4dac6]::util::bug::opt_span_bug_fmt<rustc_span[4bd220f521370a86]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x74a71394fe70 - rustc_middle[f2fffebf67d4dac6]::util::bug::bug_fmt
  16:     0x74a71823d7cd - <rustc_const_eval[fd121c9846faaa35]::interpret::operand::Immediate>::assert_matches_abi::<rustc_const_eval[fd121c9846faaa35]::interpret::eval_context::InterpCx<rustc_const_eval[fd121c9846faaa35]::const_eval::dummy_machine::DummyMachine>>.cold
  17:     0x74a71734c022 - <rustc_const_eval[fd121c9846faaa35]::interpret::operand::ImmTy>::offset_::<rustc_const_eval[fd121c9846faaa35]::interpret::eval_context::InterpCx<rustc_const_eval[fd121c9846faaa35]::const_eval::dummy_machine::DummyMachine>>
  18:     0x74a71734aa0d - <rustc_const_eval[fd121c9846faaa35]::interpret::operand::OpTy as rustc_const_eval[fd121c9846faaa35]::interpret::projection::Projectable<rustc_middle[f2fffebf67d4dac6]::mir::interpret::pointer::CtfeProvenance>>::offset_with_meta::<rustc_const_eval[fd121c9846faaa35]::const_eval::dummy_machine::DummyMachine>
  19:     0x74a717367411 - <rustc_mir_dataflow[bb806dd31a4a8e17]::value_analysis::Map>::for_each_projection_value::<rustc_const_eval[fd121c9846faaa35]::interpret::operand::OpTy, <rustc_mir_transform[8d321f23de625b13]::jump_threading::TOFinder>::process_constant::{closure#0}, <rustc_mir_transform[8d321f23de625b13]::jump_threading::TOFinder>::process_constant::{closure#1}>
  20:     0x74a717363c88 - <rustc_mir_transform[8d321f23de625b13]::jump_threading::TOFinder>::process_operand
  21:     0x74a717364283 - <rustc_mir_transform[8d321f23de625b13]::jump_threading::TOFinder>::find_opportunity
  22:     0x74a717365407 - <rustc_mir_transform[8d321f23de625b13]::jump_threading::TOFinder>::find_opportunity
  23:     0x74a7173619c4 - <rustc_mir_transform[8d321f23de625b13]::jump_threading::JumpThreading as rustc_mir_transform[8d321f23de625b13]::pass_manager::MirPass>::run_pass
  24:     0x74a7168044a2 - rustc_mir_transform[8d321f23de625b13]::pass_manager::run_passes_inner
  25:     0x74a716d5068e - rustc_mir_transform[8d321f23de625b13]::optimized_mir
  26:     0x74a716d4fe8d - rustc_query_impl[d8c178d2a03c64a0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d8c178d2a03c64a0]::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f2fffebf67d4dac6]::query::erase::Erased<[u8; 8usize]>>
  27:     0x74a716b30f9f - rustc_query_system[6dc7d387dd994d75]::query::plumbing::try_execute_query::<rustc_query_impl[d8c178d2a03c64a0]::DynamicConfig<rustc_query_system[6dc7d387dd994d75]::query::caches::DefIdCache<rustc_middle[f2fffebf67d4dac6]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d8c178d2a03c64a0]::plumbing::QueryCtxt, false>
  28:     0x74a716b3039f - rustc_query_impl[d8c178d2a03c64a0]::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace
  29:     0x74a71738a6a9 - rustc_middle[f2fffebf67d4dac6]::query::plumbing::query_get_at::<rustc_query_system[6dc7d387dd994d75]::query::caches::DefIdCache<rustc_middle[f2fffebf67d4dac6]::query::erase::Erased<[u8; 8usize]>>>
  30:     0x74a717391a71 - <rustc_metadata[5919056398511050]::rmeta::encoder::EncodeContext>::encode_crate_root
  31:     0x74a71799a468 - rustc_metadata[5919056398511050]::rmeta::encoder::encode_metadata
  32:     0x74a7177bf036 - rustc_metadata[5919056398511050]::fs::encode_and_write_metadata
  33:     0x74a7177bdece - <rustc_interface[2006dbae419e0802]::queries::Linker>::codegen_and_build_linker
  34:     0x74a7177625df - rustc_interface[2006dbae419e0802]::passes::create_and_enter_global_ctxt::<core[27041657fc19ee73]::option::Option<rustc_interface[2006dbae419e0802]::queries::Linker>, rustc_driver_impl[b88f56deeb7372ac]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  35:     0x74a717741c73 - rustc_interface[2006dbae419e0802]::interface::run_compiler::<(), rustc_driver_impl[b88f56deeb7372ac]::run_compiler::{closure#0}>::{closure#1}
  36:     0x74a7176a83f5 - std[ff511cecd2b9d7cf]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[2006dbae419e0802]::util::run_in_thread_with_globals<rustc_interface[2006dbae419e0802]::util::run_in_thread_pool_with_globals<rustc_interface[2006dbae419e0802]::interface::run_compiler<(), rustc_driver_impl[b88f56deeb7372ac]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  37:     0x74a7176a80d9 - <<std[ff511cecd2b9d7cf]::thread::Builder>::spawn_unchecked_<rustc_interface[2006dbae419e0802]::util::run_in_thread_with_globals<rustc_interface[2006dbae419e0802]::util::run_in_thread_pool_with_globals<rustc_interface[2006dbae419e0802]::interface::run_compiler<(), rustc_driver_impl[b88f56deeb7372ac]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[27041657fc19ee73]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  38:     0x74a7176a786b - std::sys::pal::unix::thread::Thread::new::thread_start::hb57557dfe1a8d225
  39:     0x74a7118a339d - <unknown>
  40:     0x74a71192849c - <unknown>
  41:                0x0 - <unknown>

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: rustc 1.86.0-nightly (6dd75f0d6 2025-02-02) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z mir-enable-passes=+Inline -Z mir-enable-passes=+JumpThreading --crate-type lib -Z dump-mir-dir=dir

query stack during panic:
#0 [optimized_mir] optimizing MIR for `problem_thingy`
end of query stack
error: aborting due to 1 previous error

cc #135020

[RalfJung]

This ICEs even without any flags:

error: internal compiler error: encountered unexpected unsized field in layout of std::option::Option<str>: TyAndLayout {
                                    ty: str,
                                    layout: Layout {
                                        size: Size(0 bytes),
                                        align: AbiAndPrefAlign {
                                            abi: Align(1 bytes),
                                            pref: Align(1 bytes),
                                        },
                                        abi: Memory {
                                            sized: false,
                                        },
                                        fields: Array {
                                            stride: Size(1 bytes),
                                            count: 0,
                                        },
                                        largest_niche: None,
                                        variants: Single {
                                            index: 0,
                                        },
                                        max_repr_align: None,
                                        unadjusted_abi_align: Align(1 bytes),
                                    },
                                }
  |
  = note: delayed at compiler/rustc_ty_utils/src/layout.rs:109:32 - disabled backtrace

Option<str> is indeed an invalid type so it's not surprising that this leads to ICEs somewhere in the interpreter when working on values of that "type".

Cc @oli-obk

[oli-obk]

According to the playground this is fixed on nightly

[RalfJung]

Ah, so ICE in the type system is gone... but it seems like the resulting program is still somehow broken, as it can cause an ICE in MIR opts. Cc @rust-lang/wg-mir-opt

Here's the ICE with debug info and debug assertions (so it fails a bit earlier as we do more consistency checks):

thread 'rustc' panicked at /home/r/src/rust/rustc/compiler/rustc_const_eval/src/interpret/operand.rs:265:9:
immediate Scalar(0x0000000000000000) does not fit to layout TyAndLayout { ty: Option<&str>, layout: Layout { size: Size(16 bytes), align: AbiAndPrefAlign { abi: Align(8 bytes), pref: Align(8 bytes) }, abi: ScalarPair(Initialized { value: Pointer(AddressSpace(0)), valid_range: (..=0) | (1..) }, Union { value: Int(I64, false) }), fields: Arbitrary { offsets: [Size(0 bytes)], memory_index: [0] }, largest_niche: None, variants: Multiple { tag: Initialized { value: Pointer(AddressSpace(0)), valid_range: (..=0) | (1..) }, tag_encoding: Niche { untagged_variant: 1, niche_variants: 0..=0, niche_start: 0 }, tag_field: 0, variants: [Layout { size: Size(0 bytes), align: AbiAndPrefAlign { abi: Align(1 bytes), pref: Align(8 bytes) }, abi: Memory { sized: true }, fields: Arbitrary { offsets: [], memory_index: [] }, largest_niche: None, variants: Single { index: 0 }, max_repr_align: None, unadjusted_abi_align: Align(1 bytes), randomization_seed: 2862809314334345461 }, Layout { size: Size(16 bytes), align: AbiAndPrefAlign { abi: Align(8 bytes), pref: Align(8 bytes) }, abi: ScalarPair(Initialized { value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }, Initialized { value: Int(I64, false), valid_range: 0..=18446744073709551615 }), fields: Arbitrary { offsets: [Size(0 bytes)], memory_index: [0] }, largest_niche: Some(Niche { offset: Size(0 bytes), value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }), variants: Single { index: 1 }, max_repr_align: None, unadjusted_abi_align: Align(8 bytes), randomization_seed: 2862809314334345477 }] }, max_repr_align: None, unadjusted_abi_align: Align(8 bytes), randomization_seed: 8588427943003036399 } }
stack backtrace:
   0: rust_begin_unwind
             at ./library/std/src/panicking.rs:695:5
   1: core::panicking::panic_fmt
             at ./library/core/src/panicking.rs:75:14
   2: <rustc_const_eval::interpret::operand::ImmTy>::from_immediate
             at ./compiler/rustc_const_eval/src/interpret/operand.rs:265:9
   3: <rustc_const_eval::interpret::operand::OpTy>::as_mplace_or_imm
             at ./compiler/rustc_const_eval/src/interpret/place.rs:320:46
   4: <rustc_const_eval::interpret::operand::OpTy as rustc_const_eval::interpret::projection::Projectable<rustc_middle::mir::interpret::pointer::CtfeProvenance>>::meta
             at ./compiler/rustc_const_eval/src/interpret/operand.rs:521:15
   5: <rustc_const_eval::interpret::eval_context::InterpCx<rustc_const_eval::const_eval::dummy_machine::DummyMachine>>::project_downcast::<rustc_const_eval::interpret::operand::OpTy>
             at ./compiler/rustc_const_eval/src/interpret/projection.rs:208:18
   6: <rustc_mir_transform::jump_threading::TOFinder>::process_constant::{closure#0}
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:397:44
   7: <rustc_mir_dataflow::value_analysis::Map>::for_each_projection_value::<rustc_const_eval::interpret::operand::OpTy, <rustc_mir_transform::jump_threading::TOFinder>::process_constant::{closure#0}, <rustc_mir_transform::jump_threading::TOFinder>::process_constant::{closure#1}>
             at ./compiler/rustc_mir_dataflow/src/value_analysis.rs:778:34
   8: <rustc_mir_transform::jump_threading::TOFinder>::process_constant
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:392:9
   9: <rustc_mir_transform::jump_threading::TOFinder>::process_operand
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:442:17
  10: <rustc_mir_transform::jump_threading::TOFinder>::process_assign
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:462:37
  11: <rustc_mir_transform::jump_threading::TOFinder>::process_statement
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:589:17
  12: <rustc_mir_transform::jump_threading::TOFinder>::find_opportunity::{closure#0}
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:262:13
  13: <rustc_mir_transform::jump_threading::TOFinder>::find_opportunity
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:235:5
  14: <rustc_mir_transform::jump_threading::TOFinder>::recurse_through_terminator::<<rustc_mir_transform::jump_threading::TOFinder>::find_opportunity::{closure#0}::{closure#1}>
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:635:9
  15: <rustc_mir_transform::jump_threading::TOFinder>::find_opportunity::{closure#0}
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:293:17
  16: <rustc_mir_transform::jump_threading::TOFinder>::find_opportunity
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:235:5
  17: <rustc_mir_transform::jump_threading::TOFinder>::start_from_switch
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:230:9
  18: <rustc_mir_transform::jump_threading::JumpThreading as rustc_mir_transform::pass_manager::MirPass>::run_pass
             at ./compiler/rustc_mir_transform/src/jump_threading.rs:93:13
  19: rustc_mir_transform::pass_manager::run_passes_inner
             at ./compiler/rustc_mir_transform/src/pass_manager.rs:291:17
  20: rustc_mir_transform::pass_manager::run_passes
             at ./compiler/rustc_mir_transform/src/pass_manager.rs:199:5
  21: rustc_mir_transform::run_optimization_passes
             at ./compiler/rustc_mir_transform/src/lib.rs:642:5
  22: rustc_mir_transform::inner_optimized_mir
             at ./compiler/rustc_mir_transform/src/lib.rs:762:5
  23: rustc_mir_transform::optimized_mir
             at ./compiler/rustc_mir_transform/src/lib.rs:720:21
  24: rustc_query_impl::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}
             at ./compiler/rustc_query_impl/src/plumbing.rs:280:13
      [... omitted 22 frames ...]
  25: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
             at ./compiler/rustc_middle/src/query/plumbing.rs:181:17
  26: <rustc_middle::query::plumbing::TyCtxtAt>::optimized_mir::<rustc_span::def_id::LocalDefId>
             at ./compiler/rustc_middle/src/query/plumbing.rs:471:31
  27: <rustc_middle::ty::context::TyCtxt>::optimized_mir::<rustc_span::def_id::LocalDefId>
             at ./compiler/rustc_middle/src/query/plumbing.rs:462:17
  28: <rustc_metadata::rmeta::encoder::EncodeContext>::encode_mir
             at ./compiler/rustc_metadata/src/rmeta/encoder.rs:1740:74
  29: <rustc_metadata::rmeta::encoder::EncodeContext>::encode_crate_root::{closure#15}
             at ./compiler/rustc_metadata/src/rmeta/encoder.rs:640:29
  30: <rustc_metadata::rmeta::encoder::EncodeContext>::encode_crate_root
             at ./compiler/rustc_metadata/src/rmeta/encoder.rs:601:27
  31: rustc_metadata::rmeta::encoder::encode_metadata
             at ./compiler/rustc_metadata/src/rmeta/encoder.rs:2337:16
  32: rustc_metadata::fs::encode_and_write_metadata
             at ./compiler/rustc_metadata/src/fs.rs:65:13
  33: rustc_interface::passes::start_codegen
             at ./compiler/rustc_interface/src/passes.rs:1047:44
  34: <rustc_interface::queries::Linker>::codegen_and_build_linker
             at ./compiler/rustc_interface/src/queries.rs:29:31
  35: rustc_driver_impl::run_compiler::{closure#0}::{closure#2}
             at ./compiler/rustc_driver_impl/src/lib.rs:374:18
  36: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
             at ./compiler/rustc_interface/src/passes.rs:813:27
  37: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}
             at ./compiler/rustc_middle/src/ty/context.rs:1395:37
  38: rustc_middle::ty::context::tls::enter_context::<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}
             at ./compiler/rustc_middle/src/ty/context/tls.rs:72:9
  39: <std::thread::local::LocalKey<core::cell::Cell<*const ()>>>::try_with::<rustc_middle::ty::context::tls::enter_context<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
             at ./library/std/src/thread/local.rs:316:12
  40: <std::thread::local::LocalKey<core::cell::Cell<*const ()>>>::with::<rustc_middle::ty::context::tls::enter_context<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
             at ./library/std/src/thread/local.rs:280:15
  41: rustc_middle::ty::context::tls::enter_context::<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>
             at ./compiler/rustc_middle/src/ty/context/tls.rs:69:5
  42: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
             at ./compiler/rustc_middle/src/ty/context.rs:1395:9
  43: <rustc_middle::ty::context::TyCtxt>::create_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}>
             at ./compiler/rustc_middle/src/ty/context.rs:1591:9
  44: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}
             at ./compiler/rustc_interface/src/passes.rs:781:9
  45: <rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
             at ./library/core/src/ops/function.rs:250:5
  46: <alloc::boxed::Box<dyn for<'a> core::ops::function::FnOnce<(&'a rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, &'a std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt<'a>>, &'a rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena<'a>>, &'a rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena<'a>>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}), Output = core::option::Option<rustc_interface::queries::Linker>>> as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once
             at ./library/alloc/src/boxed.rs:2016:9
  47: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
             at ./compiler/rustc_interface/src/passes.rs:821:5
  48: rustc_driver_impl::run_compiler::{closure#0}
             at ./compiler/rustc_driver_impl/src/lib.rs:339:22
  49: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}
             at ./compiler/rustc_interface/src/interface.rs:509:80
  50: <core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}> as core::ops::function::FnOnce<()>>::call_once
             at ./library/core/src/panic/unwind_safe.rs:272:9
  51: std::panicking::try::do_call::<core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}>, ()>
             at ./library/std/src/panicking.rs:587:40
  52: std::panicking::try::<(), core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}>>
             at ./library/std/src/panicking.rs:550:19
  53: std::panic::catch_unwind::<core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}>, ()>
             at ./library/std/src/panic.rs:358:14
  54: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
             at ./compiler/rustc_interface/src/interface.rs:509:23
  55: rustc_interface::util::run_in_thread_pool_with_globals::<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}
             at ./compiler/rustc_interface/src/util.rs:175:13
  56: rustc_interface::util::run_in_thread_with_globals::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}
             at ./compiler/rustc_interface/src/util.rs:138:21
  57: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}, ()>
             at /home/r/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/scoped-tls-1.0.1/src/lib.rs:137:9
  58: rustc_span::create_session_globals_then::<(), rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}>
             at ./compiler/rustc_span/src/lib.rs:139:5
  59: rustc_interface::util::run_in_thread_with_globals::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}
             at ./compiler/rustc_interface/src/util.rs:137:17
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Something, somewhere, is creating a value of type Option<&str> that is just a scalar null pointer without metadata. Unsurprisingly, this then explodes a bit later.

[RalfJung]

Adding -Zdump-mir shows some really odd stuff in the post-inlining MIR:

_10 = Option::<Option<str>>::get_or_insert_with::<{closure@Peekable<&mut impl Iterator<Item = str>>::peek::{closure#0}}>(move _11, move _12) -> [return: bb5, unwind continue];

And, I mean Iterator<Item = str> should just be rejected, right? The item type must be sized. It's no surprise later parts of the compiler choke on this.

[RalfJung]

The concrete source of the ICE is this in the post-inlining MIR:

    bb7: {
        _4 = const {transmute(0x0000000000000000): Option<&str>};
        goto -> bb6;
    }

(I had to patch the compiler to make it not ICE when dumping this MIR)

I think this is the None here, which is of type Option<&T>, and since in that context T: Sized, this can be turned into a ptr-sized 0. But later inlining plugs in an unsized T and then 💥

Cc @lcnr @compiler-errors -- the code in the OP used to ICE, this got "fixed" by just accepting the code but that's wrong, it needs to be rejected since it is ill-typed.