Load-bearing comment Incremental ICE

[CAD97]

This is as minimized as I could get:

Code

// mod r#impl;

#[derive(Debug)]
pub struct Parser<'src> {
    src: &'src str,
    pos: usize,
    // depth: usize,
    state: ParseState,
}

impl<'src> Parser<'src> {
    pub fn new(src: &'src str) -> Self {
        Self {
            src,
            pos: 0,
            // depth: 0,
            state: ParseState::WantNode,
        }
    }
}

#[derive(Debug, PartialEq, Eq)]
enum ParseState {
    WantNode,
    WantChild,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Event<'src> {
    BeginNode {
        slashdash: bool,
        type_annotation: Option<Identifier<'src>>,
        name: Identifier<'src>,
    },
    Argument {
        type_annotation: Option<Identifier<'src>>,
        value: &'src str,
    },
    Property {
        name: Identifier<'src>,
        type_annotation: Option<Identifier<'src>>,
        value: &'src str,
    },
    Children,
    End,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Identifier<'src> {
    Bare(&'src str),
    Escaped(&'src str),
    Raw(&'src str),
}

• cargo build
• Delete the comment on line 1 OR both lines 7 and 16
• cargo build
• ICE

Meta

This is not happening on nightly. But load bearing comments is scary enough I wanted to report this anyway.

rustc --version --verbose:

rustc 1.59.0-beta.5 (28c8a34e1 2022-01-27)
binary: rustc
commit-hash: 28c8a34e18fc05277c81328d1bbf5ed931f4d22e
commit-date: 2022-01-27
host: x86_64-pc-windows-msvc
release: 1.59.0-beta.5
LLVM version: 13.0.0

Error output

thread 'rustc' panicked at 'index out of bounds: the len is 51 but the index is 51', compiler\rustc_query_impl\src\on_disk_cache.rs:726:18
stack backtrace:
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 1.59.0-beta.5 (28c8a34e1 2022-01-27) running on x86_64-pc-windows-msvc

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type lib

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

query stack during panic:
#0 [codegen_fulfill_obligation] checking if `core::fmt::Debug` fulfills its obligations
#1 [resolve_instance] resolving instance `<&core::option::Option<Identifier> as core::fmt::Debug>::fmt`
#2 [vtable_entries] finding all vtable entries for trait core::fmt::Debug
#3 [collect_and_partition_mono_items] collect_and_partition_mono_items
#4 [exported_symbols] exported_symbols
end of query stack

Backtrace

stack backtrace:
   0:     0x7ffdad975fdf - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hcb4b39deedfbc6bf
   1:     0x7ffdad9a559a - core::fmt::write::he96346b765e36572
   2:     0x7ffdad967408 - <std::io::IoSliceMut as core::fmt::Debug>::fmt::h98885d2743aadc81
   3:     0x7ffdad979a0b - std::panicking::take_hook::h721111918dfcd5c5
   4:     0x7ffdad979504 - std::panicking::take_hook::h721111918dfcd5c5
   5:     0x7ffd486c39f9 - <rustc_middle[e8be7f10e3e30399]::ty::SymbolName as core[1d83072e00ca4c26]::fmt::Debug>::fmt
   6:     0x7ffdad97a136 - std::panicking::rust_panic_with_hook::h2757289713985cd7
   7:     0x7ffdad979f3b - <std::panicking::begin_panic_handler::StrPanicPayload as core::panic::BoxMeUp>::get::h49a8ba1714a1d465
   8:     0x7ffdad976927 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hcb4b39deedfbc6bf
   9:     0x7ffdad979c39 - rust_begin_unwind
  10:     0x7ffdad9d7ef0 - core::panicking::panic_fmt::h28161e1bada08bd1
  11:     0x7ffdad9d7eb7 - core::panicking::panic_bounds_check::hffc92e70f59f16e6
  12:     0x7ffd4bf3490b - <rustc_span[550e41ecb909559f]::span_encoding::Span as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  13:     0x7ffd4bee794c - <&[(rustc_middle[e8be7f10e3e30399]::ty::Predicate, rustc_span[550e41ecb909559f]::span_encoding::Span)] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  14:     0x7ffd4bdc7fba - rustc_query_impl[131a58ac89a902d8]::query_callbacks::diagnostic_hir_wf_check
  15:     0x7ffd4bd67003 - <rustc_middle[e8be7f10e3e30399]::ty::adt::AdtSizedConstraint as rustc_query_impl[131a58ac89a902d8]::values::Value>::from_cycle_error
  16:     0x7ffd4bd43c54 - <rustc_query_impl[131a58ac89a902d8]::Queries as rustc_middle[e8be7f10e3e30399]::ty::query::QueryEngine>::try_mark_green
  17:     0x7ffd4bed84a9 - <&[(rustc_middle[e8be7f10e3e30399]::ty::Predicate, rustc_span[550e41ecb909559f]::span_encoding::Span)] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  18:     0x7ffd4bddd7cc - <rustc_query_impl[131a58ac89a902d8]::on_disk_cache::OnDiskCache>::load_side_effects
  19:     0x7ffd4bed8598 - <&[(rustc_middle[e8be7f10e3e30399]::ty::Predicate, rustc_span[550e41ecb909559f]::span_encoding::Span)] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  20:     0x7ffd4bd8c3fa - RNvXsd_NtCs1DGqIPIOvr0_16rustc_query_impl13on_disk_cacheRINtNtNtNtCs7aJtBMv7B6j_3std11collections4hash3set7HashSetNtNtCs7iKsVne8byR_10rustc_span6def_id10LocalDefIdINtNtCs2x5CUVA4D6k_4core4hash18BuildHasherDefaultNtCshQqtYeJfeAw_10rustc_hash8FxHasherEEINtN
  21:     0x7ffd4bd8db6c - RNvXsd_NtCs1DGqIPIOvr0_16rustc_query_impl13on_disk_cacheRINtNtNtNtCs7aJtBMv7B6j_3std11collections4hash3set7HashSetNtNtCs7iKsVne8byR_10rustc_span6def_id10LocalDefIdINtNtCs2x5CUVA4D6k_4core4hash18BuildHasherDefaultNtCshQqtYeJfeAw_10rustc_hash8FxHasherEEINtN
  22:     0x7ffd4bed86a3 - <&[(rustc_middle[e8be7f10e3e30399]::ty::Predicate, rustc_span[550e41ecb909559f]::span_encoding::Span)] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  23:     0x7ffd4bd44346 - <rustc_query_impl[131a58ac89a902d8]::Queries as rustc_middle[e8be7f10e3e30399]::ty::query::QueryEngine>::try_mark_green
  24:     0x7ffd4bed84a9 - <&[(rustc_middle[e8be7f10e3e30399]::ty::Predicate, rustc_span[550e41ecb909559f]::span_encoding::Span)] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  25:     0x7ffd4bddd7cc - <rustc_query_impl[131a58ac89a902d8]::on_disk_cache::OnDiskCache>::load_side_effects
  26:     0x7ffd4bed8598 - <&[(rustc_middle[e8be7f10e3e30399]::ty::Predicate, rustc_span[550e41ecb909559f]::span_encoding::Span)] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  27:     0x7ffd4bd8c3fa - RNvXsd_NtCs1DGqIPIOvr0_16rustc_query_impl13on_disk_cacheRINtNtNtNtCs7aJtBMv7B6j_3std11collections4hash3set7HashSetNtNtCs7iKsVne8byR_10rustc_span6def_id10LocalDefIdINtNtCs2x5CUVA4D6k_4core4hash18BuildHasherDefaultNtCshQqtYeJfeAw_10rustc_hash8FxHasherEEINtN
  28:     0x7ffd4bd8dcc3 - RNvXsd_NtCs1DGqIPIOvr0_16rustc_query_impl13on_disk_cacheRINtNtNtNtCs7aJtBMv7B6j_3std11collections4hash3set7HashSetNtNtCs7iKsVne8byR_10rustc_span6def_id10LocalDefIdINtNtCs2x5CUVA4D6k_4core4hash18BuildHasherDefaultNtCshQqtYeJfeAw_10rustc_hash8FxHasherEEINtN
  29:     0x7ffd4bee4065 - <&[(rustc_middle[e8be7f10e3e30399]::ty::Predicate, rustc_span[550e41ecb909559f]::span_encoding::Span)] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  30:     0x7ffd4bd789cd - <rustc_middle[e8be7f10e3e30399]::mir::interpret::GlobalId as rustc_query_impl[131a58ac89a902d8]::keys::Key>::default_span
  31:     0x7ffd4bdd5feb - <rustc_query_impl[131a58ac89a902d8]::on_disk_cache::OnDiskCache>::load_side_effects
  32:     0x7ffd4bb133f4 - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  33:     0x7ffd4bc45037 - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  34:     0x7ffd4bd05c53 - <rustc_query_impl[131a58ac89a902d8]::Queries>::as_dyn
  35:     0x7ffd4bca568a - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  36:     0x7ffd4bd3e404 - <rustc_query_impl[131a58ac89a902d8]::Queries as rustc_middle[e8be7f10e3e30399]::ty::query::QueryEngine>::try_mark_green
  37:     0x7ffd4b221a09 - rustc_ty_utils[3781a4ad9059bb0d]::instance::provide
  38:     0x7ffd4b220286 - rustc_ty_utils[3781a4ad9059bb0d]::instance::provide
  39:     0x7ffd4bd4d163 - <rustc_query_impl[131a58ac89a902d8]::Queries as rustc_middle[e8be7f10e3e30399]::ty::query::QueryEngine>::try_mark_green
  40:     0x7ffd4bc1efec - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  41:     0x7ffd4bd05822 - <rustc_query_impl[131a58ac89a902d8]::Queries>::as_dyn
  42:     0x7ffd4bc8241d - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  43:     0x7ffd4bd3f661 - <rustc_query_impl[131a58ac89a902d8]::Queries as rustc_middle[e8be7f10e3e30399]::ty::query::QueryEngine>::try_mark_green
  44:     0x7ffd4cbd67c9 - <rustc_middle[e8be7f10e3e30399]::ty::instance::Instance>::resolve_opt_const_arg
  45:     0x7ffd4cbc839b - <rustc_middle[e8be7f10e3e30399]::ty::instance::Instance>::resolve_for_vtable
  46:     0x7ffd4c94d78f - <rustc_trait_selection[1b9055e1c4f657df]::traits::auto_trait::RegionDeps as core[1d83072e00ca4c26]::fmt::Debug>::fmt
  47:     0x7ffd4c8ff4ec - rustc_trait_selection[1b9055e1c4f657df]::traits::impossible_predicates
  48:     0x7ffd4c8fe6d4 - rustc_trait_selection[1b9055e1c4f657df]::traits::impossible_predicates
  49:     0x7ffd4bd4d961 - <rustc_query_impl[131a58ac89a902d8]::Queries as rustc_middle[e8be7f10e3e30399]::ty::query::QueryEngine>::try_mark_green
  50:     0x7ffd4bc2098d - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  51:     0x7ffd4bd0ea62 - <rustc_query_impl[131a58ac89a902d8]::Queries>::as_dyn
  52:     0x7ffd4bc7a054 - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  53:     0x7ffd4bd3e343 - <rustc_query_impl[131a58ac89a902d8]::Queries as rustc_middle[e8be7f10e3e30399]::ty::query::QueryEngine>::try_mark_green
  54:     0x7ffd4ac52a34 - <rustc_monomorphize[2d7a027cec0a5735]::collector::MirNeighborCollector as rustc_middle[e8be7f10e3e30399]::mir::visit::Visitor>::visit_operand
  55:     0x7ffd4ac506fe - <rustc_monomorphize[2d7a027cec0a5735]::collector::MirNeighborCollector as rustc_middle[e8be7f10e3e30399]::mir::visit::Visitor>::visit_rvalue
  56:     0x7ffd4ac54759 - <rustc_monomorphize[2d7a027cec0a5735]::collector::RootCollector as rustc_hir[7e355ad7be8a675b]::itemlikevisit::ItemLikeVisitor>::visit_impl_item
  57:     0x7ffd4ac4d7ae - <rustc_monomorphize[2d7a027cec0a5735]::partitioning::MonoItemPlacement as core[1d83072e00ca4c26]::fmt::Debug>::fmt
  58:     0x7ffd4ac3701e - <core[1d83072e00ca4c26]::option::Option<rustc_middle[e8be7f10e3e30399]::middle::privacy::AccessLevel> as rustc_privacy[75773fc7197fff26]::VisibilityLike>::new_min
  59:     0x7ffd4ac4bd03 - <rustc_monomorphize[2d7a027cec0a5735]::partitioning::MonoItemPlacement as core[1d83072e00ca4c26]::fmt::Debug>::fmt
  60:     0x7ffd4ac47aa3 - <rustc_monomorphize[2d7a027cec0a5735]::partitioning::default::DefaultPartitioning as rustc_monomorphize[2d7a027cec0a5735]::partitioning::Partitioner>::internalize_symbols
  61:     0x7ffd4bd4c0e3 - <rustc_query_impl[131a58ac89a902d8]::Queries as rustc_middle[e8be7f10e3e30399]::ty::query::QueryEngine>::try_mark_green
  62:     0x7ffd4be87703 - <&[rustc_ast[406c67bf1af5d1f0]::ast::InlineAsmTemplatePiece] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  63:     0x7ffd4bd295cc - <rustc_query_impl[131a58ac89a902d8]::Queries>::as_dyn
  64:     0x7ffd4bc18e6f - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  65:     0x7ffd4bce2b20 - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  66:     0x7ffd4bdb47d7 - rustc_query_impl[131a58ac89a902d8]::query_callbacks::collect_and_partition_mono_items
  67:     0x7ffd4cb17bc3 - <rustc_middle[e8be7f10e3e30399]::ty::context::TyCtxt as rustc_query_system[da7f1cc4b8055ce2]::dep_graph::DepContext>::try_force_from_dep_node
  68:     0x7ffd4beae53b - <&[rustc_ast[406c67bf1af5d1f0]::ast::InlineAsmTemplatePiece] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  69:     0x7ffd4beae1aa - <&[rustc_ast[406c67bf1af5d1f0]::ast::InlineAsmTemplatePiece] as rustc_serialize[7a7d8c4496902bcc]::serialize::Decodable<rustc_query_impl[131a58ac89a902d8]::on_disk_cache::CacheDecoder>>::decode
  70:     0x7ffd4bc3e56d - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  71:     0x7ffd4bd0f3c2 - <rustc_query_impl[131a58ac89a902d8]::Queries>::as_dyn
  72:     0x7ffd4bbe680b - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  73:     0x7ffd4bc7f093 - <rustc_mir_dataflow[752d4053f08c2531]::impls::storage_liveness::MaybeRequiresStorage as rustc_mir_dataflow[752d4053f08c2531]::framework::AnalysisDomain>::initialize_start_block
  74:     0x7ffd4c243bb3 - <rustc_metadata[5db6f7f4bfa8fe45]::rmeta::encoder::EncodeContext as rustc_middle[e8be7f10e3e30399]::ty::codec::TyEncoder>::encode_alloc_id
  75:     0x7ffd4c25b940 - rustc_metadata[5db6f7f4bfa8fe45]::rmeta::encoder::encode_metadata
  76:     0x7ffd4c2b7325 - <u32 as rustc_metadata[5db6f7f4bfa8fe45]::rmeta::table::FixedSizeEncoding>::write_to_bytes_at
  77:     0x7ffd4c25aff3 - rustc_metadata[5db6f7f4bfa8fe45]::rmeta::encoder::encode_metadata
  78:     0x7ffd487c8b6c - <rustc_interface[31ce9d8f7019e821]::queries::Queries>::ongoing_codegen
  79:     0x7ffd4867563f - <rustc_driver[45305811ac36932b]::args::Error as core[1d83072e00ca4c26]::fmt::Debug>::fmt
  80:     0x7ffd486524e5 - <sha2[b9a4e930306da819]::sha512::Sha512 as std[538cbe44b3125595]::io::Write>::flush
  81:     0x7ffd48672f91 - <sha2[b9a4e930306da819]::sha512::Sha512 as std[538cbe44b3125595]::io::Write>::flush
  82:     0x7ffd48655ac7 - <sha2[b9a4e930306da819]::sha512::Sha512 as std[538cbe44b3125595]::io::Write>::flush
  83:     0x7ffd4865470c - <sha2[b9a4e930306da819]::sha512::Sha512 as std[538cbe44b3125595]::io::Write>::flush
  84:     0x7ffd48678f08 - <rustc_middle[e8be7f10e3e30399]::ty::SymbolName as core[1d83072e00ca4c26]::fmt::Debug>::fmt
  85:     0x7ffdad98a0ac - std::sys::windows::thread::Thread::new::h221b319dbb2805a7
  86:     0x7ffdea3f7034 - BaseThreadInitThunk
  87:     0x7ffdeb322651 - RtlUserThreadStart

[CAD97]

If I had to guess, #93066 seems very relevant as what could've fixed this.

the blamed line:

rust/compiler/rustc_query_impl/src/on_disk_cache.rs

Line 726 in 0426998

let lo = file_lo.lines[line_lo - 1] + col_lo;

Context

rust/compiler/rustc_query_impl/src/on_disk_cache.rs

Lines 694 to 731 in 0426998

	impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for Span {
	fn decode(decoder: &mut CacheDecoder<'a, 'tcx>) -> Result<Self, String> {
	let ctxt = SyntaxContext::decode(decoder)?;
	let parent = Option::<LocalDefId>::decode(decoder)?;
	let tag: u8 = Decodable::decode(decoder)?;
	if tag == TAG_PARTIAL_SPAN {
	return Ok(Span::new(BytePos(0), BytePos(0), ctxt, parent));
	} else if tag == TAG_RELATIVE_SPAN {
	let dlo = u32::decode(decoder)?;
	let dto = u32::decode(decoder)?;
	let enclosing =
	decoder.tcx.definitions_untracked().def_span(parent.unwrap()).data_untracked();
	let span = Span::new(
	enclosing.lo + BytePos::from_u32(dlo),
	enclosing.lo + BytePos::from_u32(dto),
	ctxt,
	parent,
	);
	return Ok(span);
	} else {
	debug_assert_eq!(tag, TAG_FULL_SPAN);
	}
	let file_lo_index = SourceFileIndex::decode(decoder)?;
	let line_lo = usize::decode(decoder)?;
	let col_lo = BytePos::decode(decoder)?;
	let len = BytePos::decode(decoder)?;
	let file_lo = decoder.file_index_to_file(file_lo_index);
	let lo = file_lo.lines[line_lo - 1] + col_lo;
	let hi = lo + len;
	Ok(Span::new(lo, hi, ctxt, parent))
	}
	}

Current

rust/compiler/rustc_query_impl/src/on_disk_cache.rs

Lines 683 to 720 in 27f5d83

	impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for Span {
	fn decode(decoder: &mut CacheDecoder<'a, 'tcx>) -> Self {
	let ctxt = SyntaxContext::decode(decoder);
	let parent = Option::<LocalDefId>::decode(decoder);
	let tag: u8 = Decodable::decode(decoder);
	if tag == TAG_PARTIAL_SPAN {
	return Span::new(BytePos(0), BytePos(0), ctxt, parent);
	} else if tag == TAG_RELATIVE_SPAN {
	let dlo = u32::decode(decoder);
	let dto = u32::decode(decoder);
	let enclosing =
	decoder.tcx.definitions_untracked().def_span(parent.unwrap()).data_untracked();
	let span = Span::new(
	enclosing.lo + BytePos::from_u32(dlo),
	enclosing.lo + BytePos::from_u32(dto),
	ctxt,
	parent,
	);
	return span;
	} else {
	debug_assert_eq!(tag, TAG_FULL_SPAN);
	}
	let file_lo_index = SourceFileIndex::decode(decoder);
	let line_lo = usize::decode(decoder);
	let col_lo = BytePos::decode(decoder);
	let len = BytePos::decode(decoder);
	let file_lo = decoder.file_index_to_file(file_lo_index);
	let lo = file_lo.lines[line_lo - 1] + col_lo;
	let hi = lo + len;
	Span::new(lo, hi, ctxt, parent)
	}
	}

The reason for it to not panic anymore isn't localized here, so I can't track it down. cc @nnethercote, any ideas what could've caused this change?

[nnethercote]

I can't see how #93066 would affect this. The only likely behavioural changes that PR would cause is that if problems occurred with metadata decoding (e.g. corrupted metadata) then rustc would panic a bit earlier than it did previously.

@Aaron1011 You've been looking a lot at incremental issues lately, any ideas about this one?

[Aaron1011]

I don't think this is caused by the comment itself, but by the change in line numbers triggered by adding/removing lines.

[CAD97]

It does seem to be due to span data changing, but it's interesting in how inconsistent it is; changes in some places are fine, and some aren't.

(And if you're keeping it rustfmtd, it translates to load bearing comments keeping it from reformatting into an ICE.)

In any case, this has been incidentally fixed (suppressed?) by changes between beta and nightly, so I don't know how much investigation this is actually worth. At least it's an ICE rather than a miscomp. Incremental issues spook me.

[CAD97]

Given that this no longer occurs, I'm going to go ahead and close this.