ICE: `assertion failed: bpos.to_u32() >= mbc.pos.to_u32() + mbc.bytes as u32'`

[matthiaskrgr]

auto-reduced (treereduce-rust):

pub fn foo3<'a>(_other: &'a [u8], x: ＆ Vec<&u8>, y: &u8) { x.push(y); } 

original:

pub fn foo(x: &mut Vec<&'a T>, y: Ref<'b>) { x.push(y); } //~ ERROR lifetime may not live long enough

pub fn foo2(x: &mut Vec<&'_ u8>, y: &u8) { x.push(y); } //~ ERROR lifetime may not live long enough

pub fn foo3<'a>(_other: &'a [u8], x: ＆ Vec<&u8>, y: &u8) { x.push(y); } //~ ERROR lifetime may not live long enough

fn main() {}

Version information

rustc 1.87.0-nightly (2a0602295 2025-03-28)
binary: rustc
commit-hash: 2a06022951893fe5b5384f8dbd75b4e6e3b5cee0
commit-date: 2025-03-28
host: x86_64-unknown-linux-gnu
release: 1.87.0-nightly
LLVM version: 20.1.1

Possibly related line of code:

rust/compiler/rustc_span/src/lib.rs

Lines 2241 to 2253 in 2a06022

	if mbc.pos < bpos {
	// Every character is at least one byte, so we only
	// count the actual extra bytes.
	total_extra_bytes += mbc.bytes as u32 - 1;
	// We should never see a byte position in the middle of a
	// character.
	assert!(bpos.to_u32() >= mbc.pos.to_u32() + mbc.bytes as u32);
	} else {
	break;
	}
	}
	assert!(total_extra_bytes <= bpos.to_u32());

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error: unknown start of token: \u{ff06}
 --> /tmp/icemaker_global_tempdir.NM2ythOfXGaf/rustc_testrunner_tmpdir_reporting.uxIClsJjlvJ7/mvce.rs:5:38
  |
5 | pub fn foo3<'a>(_other: &'a [u8], x: ＆ Vec<&u8>, y: &u8) { x.push(y); } 
  |                                      ^^
  |
help: Unicode character '＆' (Fullwidth Ampersand) looks like '&' (Ampersand), but it is not
  |
5 - pub fn foo3<'a>(_other: &'a [u8], x: ＆ Vec<&u8>, y: &u8) { x.push(y); } 
5 + pub fn foo3<'a>(_other: &'a [u8], x: & Vec<&u8>, y: &u8) { x.push(y); } 
  |

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.NM2ythOfXGaf/rustc_testrunner_tmpdir_reporting.uxIClsJjlvJ7/mvce.rs:5:72
  |
5 | pub fn foo3<'a>(_other: &'a [u8], x: ＆ Vec<&u8>, y: &u8) { x.push(y); } 
  |                                                                         ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.NM2ythOfXGaf/rustc_testrunner_tmpdir_reporting.uxIClsJjlvJ7/mvce.rs`

error[E0596]: cannot borrow `*x` as mutable, as it is behind a `&` reference
 --> /tmp/icemaker_global_tempdir.NM2ythOfXGaf/rustc_testrunner_tmpdir_reporting.uxIClsJjlvJ7/mvce.rs:5:60
  |
5 | pub fn foo3<'a>(_other: &'a [u8], x: ＆ Vec<&u8>, y: &u8) { x.push(y); } 
  |                                                             ^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
  |

thread 'rustc' panicked at compiler/rustc_span/src/lib.rs:2247:17:
assertion failed: bpos.to_u32() >= mbc.pos.to_u32() + mbc.bytes as u32
stack backtrace:
   0:     0x7d4609077313 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hec1be6b515a4b985
   1:     0x7d4609805d91 - core::fmt::write::h1a721e23ea933c95
   2:     0x7d460ac8da51 - std::io::Write::write_fmt::h8aaeee0f3c8d3f0a
   3:     0x7d4609077172 - std::sys::backtrace::BacktraceLock::print::h5669ce1c06d4f78b
   4:     0x7d4609079a2a - std::panicking::default_hook::{{closure}}::h266748ebbae7c4be
   5:     0x7d46090795af - std::panicking::default_hook::hc3bb6e6c093f4ea4
   6:     0x7d46080e39b0 - std[4597d80d7047b022]::panicking::update_hook::<alloc[772d3812010e97a3]::boxed::Box<rustc_driver_impl[1d133c6972a1a6b9]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7d460907a2a3 - std::panicking::rust_panic_with_hook::h51ac92c4d270e86c
   8:     0x7d4609079f66 - std::panicking::begin_panic_handler::{{closure}}::h8eaa2cc0543eec41
   9:     0x7d46090777e9 - std::sys::backtrace::__rust_end_short_backtrace::h733c2f162ba57005
  10:     0x7d4609079c5d - __rustc[5fbf492971bd0060]::rust_begin_unwind
  11:     0x7d4605a92e70 - core::panicking::panic_fmt::h7438f3740b41962a
  12:     0x7d460671a4dc - core::panicking::panic::h654f603cc4632f97
  13:     0x7d460a0275c4 - <rustc_span[c4947a62e1591df3]::source_map::SourceMap>::lookup_char_pos
  14:     0x7d460a65f891 - <rustc_span[c4947a62e1591df3]::source_map::SourceMap>::is_valid_span
  15:     0x7d460a65fcfc - <core[d013d7c9d10039cf]::iter::adapters::filter_map::FilterMap<core[d013d7c9d10039cf]::iter::adapters::cloned::Cloned<core[d013d7c9d10039cf]::iter::adapters::filter::Filter<core[d013d7c9d10039cf]::slice::iter::Iter<rustc_errors[7964d5e4d9f7f11a]::Substitution>, <rustc_errors[7964d5e4d9f7f11a]::CodeSuggestion>::splice_lines::{closure#0}>>, <rustc_errors[7964d5e4d9f7f11a]::CodeSuggestion>::splice_lines::{closure#1}> as core[d013d7c9d10039cf]::iter::traits::iterator::Iterator>::next
  16:     0x7d460a662392 - <rustc_errors[7964d5e4d9f7f11a]::emitter::HumanEmitter>::emit_suggestion_default
  17:     0x7d460a01ed93 - <rustc_errors[7964d5e4d9f7f11a]::emitter::HumanEmitter as rustc_errors[7964d5e4d9f7f11a]::emitter::Emitter>::emit_diagnostic
  18:     0x7d460a66ff75 - <rustc_errors[7964d5e4d9f7f11a]::DiagCtxtInner>::emit_diagnostic::{closure#3}
  19:     0x7d460a672e4d - rustc_interface[838c222bb47cac2d]::callbacks::track_diagnostic::<core[d013d7c9d10039cf]::option::Option<rustc_span[c4947a62e1591df3]::ErrorGuaranteed>>
  20:     0x7d460a6719a2 - <rustc_errors[7964d5e4d9f7f11a]::DiagCtxtInner>::emit_diagnostic
  21:     0x7d460a67185f - <rustc_errors[7964d5e4d9f7f11a]::DiagCtxtHandle>::emit_diagnostic
  22:     0x7d460ac3dfea - <rustc_span[c4947a62e1591df3]::ErrorGuaranteed as rustc_errors[7964d5e4d9f7f11a]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  23:     0x7d460a9e8949 - rustc_borrowck[b30cfce8d6e8f762]::do_mir_borrowck
  24:     0x7d460a99aeec - rustc_query_impl[3289d2c66c00b6f8]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[3289d2c66c00b6f8]::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[8492cbf8fcfbb736]::query::erase::Erased<[u8; 8usize]>>
  25:     0x7d4609b3c96c - rustc_query_system[87ba3fee088a6fc4]::query::plumbing::try_execute_query::<rustc_query_impl[3289d2c66c00b6f8]::DynamicConfig<rustc_data_structures[44af7552550bcb5]::vec_cache::VecCache<rustc_span[c4947a62e1591df3]::def_id::LocalDefId, rustc_middle[8492cbf8fcfbb736]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[87ba3fee088a6fc4]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[3289d2c66c00b6f8]::plumbing::QueryCtxt, false>
  26:     0x7d4609b3c3cb - rustc_query_impl[3289d2c66c00b6f8]::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
  27:     0x7d460a142353 - rustc_interface[838c222bb47cac2d]::passes::run_required_analyses
  28:     0x7d460a21fc9e - rustc_interface[838c222bb47cac2d]::passes::analysis
  29:     0x7d460a21fc6d - rustc_query_impl[3289d2c66c00b6f8]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[3289d2c66c00b6f8]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[8492cbf8fcfbb736]::query::erase::Erased<[u8; 0usize]>>
  30:     0x7d460a7bc3fd - rustc_query_system[87ba3fee088a6fc4]::query::plumbing::try_execute_query::<rustc_query_impl[3289d2c66c00b6f8]::DynamicConfig<rustc_query_system[87ba3fee088a6fc4]::query::caches::SingleCache<rustc_middle[8492cbf8fcfbb736]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[3289d2c66c00b6f8]::plumbing::QueryCtxt, false>
  31:     0x7d460a7bc0f8 - rustc_query_impl[3289d2c66c00b6f8]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  32:     0x7d460aac874d - rustc_interface[838c222bb47cac2d]::passes::create_and_enter_global_ctxt::<core[d013d7c9d10039cf]::option::Option<rustc_interface[838c222bb47cac2d]::queries::Linker>, rustc_driver_impl[1d133c6972a1a6b9]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  33:     0x7d460a9651aa - rustc_interface[838c222bb47cac2d]::interface::run_compiler::<(), rustc_driver_impl[1d133c6972a1a6b9]::run_compiler::{closure#0}>::{closure#1}
  34:     0x7d460a778148 - std[4597d80d7047b022]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[838c222bb47cac2d]::util::run_in_thread_with_globals<rustc_interface[838c222bb47cac2d]::util::run_in_thread_pool_with_globals<rustc_interface[838c222bb47cac2d]::interface::run_compiler<(), rustc_driver_impl[1d133c6972a1a6b9]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  35:     0x7d460a778a34 - <<std[4597d80d7047b022]::thread::Builder>::spawn_unchecked_<rustc_interface[838c222bb47cac2d]::util::run_in_thread_with_globals<rustc_interface[838c222bb47cac2d]::util::run_in_thread_pool_with_globals<rustc_interface[838c222bb47cac2d]::interface::run_compiler<(), rustc_driver_impl[1d133c6972a1a6b9]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[d013d7c9d10039cf]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  36:     0x7d460a779e37 - std::sys::pal::unix::thread::Thread::new::thread_start::h287c1faba384eaa8
  37:     0x7d46046a370a - <unknown>
  38:     0x7d4604727aac - <unknown>
  39:                0x0 - <unknown>

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

note: rustc 1.87.0-nightly (2a0602295 2025-03-28) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [mir_borrowck] borrow-checking `foo3`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0596, E0601.
For more information about an error, try `rustc --explain E0596`.

[matthiaskrgr]

Regression in nightly-2024-02-09

  commit[0] 2024-02-07: Auto merge of #120748 - Nadrieril:rollup-dj0qwv5, r=Nadrieril
  commit[1] 2024-02-08: Auto merge of #120381 - fee1-dead-contrib:reconstify-add, r=compiler-errors
  commit[2] 2024-02-08: Auto merge of #120521 - reitermarkus:generic-nonzero-constructors, r=dtolnay
  commit[3] 2024-02-08: Auto merge of #120558 - oli-obk:missing_impl_item_ice, r=estebank
  commit[4] 2024-02-08: Auto merge of #120579 - GuillaumeGomez:prevent-running-unneeded-code, r=notriddle
  commit[5] 2024-02-08: Auto merge of #120550 - oli-obk:track_errors8, r=estebank
  commit[6] 2024-02-08: Auto merge of #120767 - matthiaskrgr:rollup-0k8ib1c, r=matthiaskrgr
  commit[7] 2024-02-08: Auto merge of #120544 - BoxyUwU:enter_forall, r=lcnr
  commit[8] 2024-02-08: Auto merge of #120807 - matthiaskrgr:rollup-1pf3glu, r=matthiaskrgr

[cyrgani]

smaller:

pub fn foo3(x: ＆Vec<u8>) { x.push(0); } 

[moxian]

• Continue to borrowck even if there were previous errors #120550 sounds most likely candidate from the bisection

@rustbot label: +A-frontend +A-parser +A-borrow-checker +A-error-handling -needs-triage +S-has-mcve +S-has-bisection