ICE: sty: called `Option::unwrap()` on a `None` value

[matthiaskrgr]

snippet:

struct A<const X: usize> {
    x: Vec<&'pin mut Self> = Vec::new(),
}

Version information

rustc 1.87.0-nightly (7c4a55c2a 2025-03-02)
binary: rustc
commit-hash: 7c4a55c2ac6497629c273ccd00e185583542f0d2
commit-date: 2025-03-02
host: x86_64-unknown-linux-gnu
release: 1.87.0-nightly
LLVM version: 20.1.0

Possibly related line of code:

rust/compiler/rustc_middle/src/ty/sty.rs

Lines 356 to 368 in 7c4a55c

	}
	}
	_ => None,
	}
	});
	let ty = candidates.next().unwrap();
	assert!(candidates.next().is_none());
	ty
	}
	}
	#[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zincremental-verify-ich=yes -Cincremental=<dir> -Cdebuginfo=2 -Clink-dead-code=true -Zvalidate-mir --edition=2024

Program output

error[E0261]: use of undeclared lifetime name `'pin`
 --> /tmp/icemaker_global_tempdir.M9ihYdd57QVg/rustc_testrunner_tmpdir_reporting.ySMuC7g3iyRl/mvce.rs:2:13
  |
1 | struct A<const X: usize> {
  |          - help: consider introducing lifetime `'pin` here: `'pin,`
2 |     x: Vec<&'pin mut Self> = Vec::new(),
  |             ^^^^ undeclared lifetime

error[E0658]: default values on fields are experimental
 --> /tmp/icemaker_global_tempdir.M9ihYdd57QVg/rustc_testrunner_tmpdir_reporting.ySMuC7g3iyRl/mvce.rs:2:27
  |
2 |     x: Vec<&'pin mut Self> = Vec::new(),
  |                           ^^^^^^^^^^^^^
  |
  = note: see issue #132162 <https://github.com/rust-lang/rust/issues/132162> for more information
  = help: add `#![feature(default_field_values)]` to the crate attributes to enable
  = note: this compiler was built on 2025-03-02; consider upgrading it if it is out of date

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.M9ihYdd57QVg/rustc_testrunner_tmpdir_reporting.ySMuC7g3iyRl/mvce.rs:3:2
  |
3 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.M9ihYdd57QVg/rustc_testrunner_tmpdir_reporting.ySMuC7g3iyRl/mvce.rs`


thread 'rustc' panicked at compiler/rustc_middle/src/ty/sty.rs:362:36:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7327865bef14 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hc495f1899fa849d6
   1:     0x732786e057e2 - core::fmt::write::h39ac2b6780eacb0b
   2:     0x7327881e5291 - std::io::Write::write_fmt::hce3ca50e4f9c3d70
   3:     0x7327865bed72 - std::sys::backtrace::BacktraceLock::print::h6721b52240ac06b8
   4:     0x7327865c1652 - std::panicking::default_hook::{{closure}}::h7fd0541ed74fb3ce
   5:     0x7327865c1244 - std::panicking::default_hook::hccc7d640d5ba2811
   6:     0x732785718a87 - std[673d9073d68e8c5f]::panicking::update_hook::<alloc[956ce29f8aa768f9]::boxed::Box<rustc_driver_impl[6af4072765422930]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7327865c1ec3 - std::panicking::rust_panic_with_hook::h0da458b51069d3a7
   8:     0x7327865c1b86 - std::panicking::begin_panic_handler::{{closure}}::ha16ec4ccc9cec913
   9:     0x7327865bf3d9 - std::sys::backtrace::__rust_end_short_backtrace::h2aacb06ecfcbe368
  10:     0x7327865c187d - rust_begin_unwind
  11:     0x73278325b930 - core::panicking::panic_fmt::h41765f7bbf5784a9
  12:     0x732783cbc44c - core::panicking::panic::h9beefec10d0ae431
  13:     0x732783ac04b9 - core::option::unwrap_failed::haed1e72e8d3dc5a5
  14:     0x732788a33f66 - <rustc_middle[149f66fe1de159a6]::ty::sty::ParamConst>::find_ty_from_env.cold
  15:     0x7327876e14fb - <rustc_trait_selection[7cd3b6c2e2dd783b]::traits::fulfill::FulfillProcessor as rustc_data_structures[c5d5d3efdb2e4cc2]::obligation_forest::ObligationProcessor>::process_obligation
  16:     0x732786e074e9 - <rustc_data_structures[c5d5d3efdb2e4cc2]::obligation_forest::ObligationForest<rustc_trait_selection[7cd3b6c2e2dd783b]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[7cd3b6c2e2dd783b]::traits::fulfill::FulfillProcessor>
  17:     0x73278793f523 - <rustc_hir_typeck[22905d68007d48b0]::fn_ctxt::FnCtxt>::check_expr_path
  18:     0x732787c4ccca - <rustc_hir_typeck[22905d68007d48b0]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  19:     0x732787c4e80b - <rustc_hir_typeck[22905d68007d48b0]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  20:     0x7327871395f5 - <rustc_hir_typeck[22905d68007d48b0]::fn_ctxt::FnCtxt>::check_expr_coercible_to_type
  21:     0x73278720b161 - rustc_hir_typeck[22905d68007d48b0]::typeck_with_inspect::{closure#0}
  22:     0x732787207fb0 - rustc_query_impl[ad7e806203de0335]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ad7e806203de0335]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 8usize]>>
  23:     0x7327871fe9c8 - rustc_query_system[30512ec7f96497de]::query::plumbing::try_execute_query::<rustc_query_impl[ad7e806203de0335]::DynamicConfig<rustc_data_structures[c5d5d3efdb2e4cc2]::vec_cache::VecCache<rustc_span[8b0dd42cecff55ed]::def_id::LocalDefId, rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[30512ec7f96497de]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[ad7e806203de0335]::plumbing::QueryCtxt, true>
  24:     0x7327871fb107 - rustc_query_impl[ad7e806203de0335]::query_impl::typeck::get_query_incr::__rust_end_short_backtrace
  25:     0x7327871fce81 - rustc_query_impl[ad7e806203de0335]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ad7e806203de0335]::query_impl::used_trait_imports::dynamic_query::{closure#2}::{closure#0}, rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 8usize]>>
  26:     0x7327871fe9c8 - rustc_query_system[30512ec7f96497de]::query::plumbing::try_execute_query::<rustc_query_impl[ad7e806203de0335]::DynamicConfig<rustc_data_structures[c5d5d3efdb2e4cc2]::vec_cache::VecCache<rustc_span[8b0dd42cecff55ed]::def_id::LocalDefId, rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[30512ec7f96497de]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[ad7e806203de0335]::plumbing::QueryCtxt, true>
  27:     0x73278701b178 - rustc_query_impl[ad7e806203de0335]::query_impl::used_trait_imports::get_query_incr::__rust_end_short_backtrace
  28:     0x732787660594 - rustc_middle[149f66fe1de159a6]::query::plumbing::query_get_at::<rustc_data_structures[c5d5d3efdb2e4cc2]::vec_cache::VecCache<rustc_span[8b0dd42cecff55ed]::def_id::LocalDefId, rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[30512ec7f96497de]::dep_graph::graph::DepNodeIndex>>
  29:     0x73278765fcad - rustc_hir_analysis[21d9bf831ff42857]::check_unused::check_unused_traits
  30:     0x73278765fa07 - rustc_query_impl[ad7e806203de0335]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ad7e806203de0335]::query_impl::check_unused_traits::dynamic_query::{closure#2}::{closure#0}, rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 0usize]>>
  31:     0x732787ebda1f - rustc_query_system[30512ec7f96497de]::query::plumbing::try_execute_query::<rustc_query_impl[ad7e806203de0335]::DynamicConfig<rustc_query_system[30512ec7f96497de]::query::caches::SingleCache<rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[ad7e806203de0335]::plumbing::QueryCtxt, true>
  32:     0x732787ebcd8c - rustc_query_impl[ad7e806203de0335]::query_impl::check_unused_traits::get_query_incr::__rust_end_short_backtrace
  33:     0x7327871fa2b7 - rustc_hir_analysis[21d9bf831ff42857]::check_crate
  34:     0x7327871f3c9c - rustc_interface[d8c24ebf2384fa83]::passes::run_required_analyses
  35:     0x732787d3efba - rustc_interface[d8c24ebf2384fa83]::passes::analysis
  36:     0x732787d3ef99 - rustc_query_impl[ad7e806203de0335]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ad7e806203de0335]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 0usize]>>
  37:     0x732787ebd8aa - rustc_query_system[30512ec7f96497de]::query::plumbing::try_execute_query::<rustc_query_impl[ad7e806203de0335]::DynamicConfig<rustc_query_system[30512ec7f96497de]::query::caches::SingleCache<rustc_middle[149f66fe1de159a6]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[ad7e806203de0335]::plumbing::QueryCtxt, true>
  38:     0x732787ebd2a2 - rustc_query_impl[ad7e806203de0335]::query_impl::analysis::get_query_incr::__rust_end_short_backtrace
  39:     0x732787d72efd - rustc_interface[d8c24ebf2384fa83]::passes::create_and_enter_global_ctxt::<core[fd72b707659d9093]::option::Option<rustc_interface[d8c24ebf2384fa83]::queries::Linker>, rustc_driver_impl[6af4072765422930]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  40:     0x732787f11220 - rustc_interface[d8c24ebf2384fa83]::interface::run_compiler::<(), rustc_driver_impl[6af4072765422930]::run_compiler::{closure#0}>::{closure#1}
  41:     0x732787d53cc8 - std[673d9073d68e8c5f]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[d8c24ebf2384fa83]::util::run_in_thread_with_globals<rustc_interface[d8c24ebf2384fa83]::util::run_in_thread_pool_with_globals<rustc_interface[d8c24ebf2384fa83]::interface::run_compiler<(), rustc_driver_impl[6af4072765422930]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  42:     0x732787d545b4 - <<std[673d9073d68e8c5f]::thread::Builder>::spawn_unchecked_<rustc_interface[d8c24ebf2384fa83]::util::run_in_thread_with_globals<rustc_interface[d8c24ebf2384fa83]::util::run_in_thread_pool_with_globals<rustc_interface[d8c24ebf2384fa83]::interface::run_compiler<(), rustc_driver_impl[6af4072765422930]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[fd72b707659d9093]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  43:     0x732787d559b7 - std::sys::pal::unix::thread::Thread::new::thread_start::hb86ea38ca4860a5f
  44:     0x732781ea370a - <unknown>
  45:     0x732781f27aac - <unknown>
  46:                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 (7c4a55c2a 2025-03-02) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z incremental-verify-ich=yes -C incremental=[REDACTED] -C debuginfo=2 -C link-dead-code=true -Z validate-mir

query stack during panic:
#0 [typeck] type-checking `A::x::{constant#0}`
#1 [used_trait_imports] finding used_trait_imports `A::x::{constant#0}`
#2 [check_unused_traits] checking unused trait imports in crate
#3 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0261, E0601, E0658.
For more information about an error, try `rustc --explain E0261`.

[matthiaskrgr]

bisects to #129514

[cyrgani]

struct A<const X: usize> {
    x: Vec<Self> = Vec::new(),
}

[compiler-errors]

Less dependent on libstd:

use std::marker::PhantomData;

struct W<T>(PhantomData<T>);

impl<T> W<T> {
    const fn new() -> Self { W(PhantomData) }
}

struct Z<const X: usize> {
    x: W<Self> = W::new(),
}