nightly ICE when building flexstr in release mode

[farnoy]

Repro steps:

$ git clone https://github.com/nu11ptr/flexstr.git && cd flexstr
$ rustup override set nightly
$ rustup show
# ...
active toolchain
----------------

nightly-x86_64-pc-windows-msvc (directory override for 'C:\Projects\flexstr')
rustc 1.81.0-nightly (4bc39f028 2024-06-26)
$ cargo build --release
# ...
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: please attach the file at `C:\Projects\flexstr\rustc-ice-2024-06-27T09_40_04-37164.txt` to your bug report

note: compiler flags: --crate-type lib -C opt-level=3 -C embed-bitcode=no -C strip=debuginfo

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

query stack during panic:
#0 [evaluate_obligation] evaluating trait selection obligation `[core::mem::maybe_uninit::MaybeUninit<u8>; PAD2]: core::marker::Copy`
#1 [is_copy_raw] computing whether `[core::mem::maybe_uninit::MaybeUninit<u8>; PAD2]` is `Copy`
end of query stack

I did not bisect, but nightly-2024-04-15 does work just fine

thread 'rustc' panicked at compiler\rustc_middle\src\ty\sty.rs:360:36:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7ff97cd4d5a3 - std::backtrace_rs::backtrace::dbghelp64::trace
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\..\..\backtrace\src\backtrace\dbghelp64.rs:91
   1:     0x7ff97cd4d5a3 - std::backtrace_rs::backtrace::trace_unsynchronized
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\..\..\backtrace\src\backtrace\mod.rs:66
   2:     0x7ff97cd4d5a3 - std::backtrace::Backtrace::create
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\backtrace.rs:331
   3:     0x7ff97cd4d4ea - std::backtrace::Backtrace::force_capture
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\backtrace.rs:312
   4:     0x7ff950da0e41 - memchr
   5:     0x7ff97cd67207 - alloc::boxed::impl$50::call
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\alloc\src\boxed.rs:2078
   6:     0x7ff97cd67207 - std::panicking::rust_panic_with_hook
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\panicking.rs:804
   7:     0x7ff97cd66fdf - std::panicking::begin_panic_handler::closure$0
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\panicking.rs:663
   8:     0x7ff97cd644bf - std::sys::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\sys\backtrace.rs:171
   9:     0x7ff97cd66c76 - std::panicking::begin_panic_handler
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\panicking.rs:661
  10:     0x7ff97cdbcbc4 - core::panicking::panic_fmt
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\core\src\panicking.rs:74
  11:     0x7ff97cdbcc6d - core::panicking::panic
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\core\src\panicking.rs:148
  12:     0x7ff97cdbcb2e - core::option::unwrap_failed
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\core\src\option.rs:2013
  13:     0x7ff94f7cff01 - <rustc_middle[d84a46905b9833cf]::ty::sty::ParamConst>::find_ty_from_env
  14:     0x7ff9506bd5d7 - <rustc_trait_selection[ce8e559b29610d30]::traits::query::normalize::QueryNormalizer as rustc_type_ir[aefdc4761e7ea19c]::fold::FallibleTypeFolder<rustc_middle[d84a46905b9833cf]::ty::context::TyCtxt>>::try_fold_ty
  15:     0x7ff9506bf2fe - <rustc_trait_selection[ce8e559b29610d30]::traits::query::normalize::QueryNormalizer as rustc_type_ir[aefdc4761e7ea19c]::fold::FallibleTypeFolder<rustc_middle[d84a46905b9833cf]::ty::context::TyCtxt>>::try_fold_ty
  16:     0x7ff95061084e - <rustc_trait_selection[ce8e559b29610d30]::traits::select::SelectionContext>::evaluate_root_obligation
  17:     0x7ff94ff6cd57 - rustc_traits[8fc914267bf48580]::evaluate_obligation::evaluate_obligation
  18:     0x7ff95033d43e - rustc_query_impl[16b8175ba1dd8f83]::plumbing::query_key_hash_verify_all
  19:     0x7ff95023db0f - rustc_ty_utils[7a4117f0c994b440]::ty::self_ty_of_trait_impl_enabling_order_dep_trait_object_hack
  20:     0x7ff95034fca0 - rustc_query_impl[16b8175ba1dd8f83]::plumbing::query_key_hash_verify_all
  21:     0x7ff95067f7de - <rustc_infer[d17335e7fed5b4ff]::infer::InferCtxt as rustc_trait_selection[ce8e559b29610d30]::traits::query::evaluate_obligation::InferCtxtExt>::evaluate_obligation_no_overflow
  22:     0x7ff95062e392 - rustc_trait_selection[ce8e559b29610d30]::traits::type_known_to_meet_bound_modulo_regions
  23:     0x7ff9501b822b - rustc_ty_utils[7a4117f0c994b440]::common_traits::is_copy_raw
  24:     0x7ff95033c44b - rustc_query_impl[16b8175ba1dd8f83]::plumbing::query_key_hash_verify_all
  25:     0x7ff95024b8cc - rustc_ty_utils[7a4117f0c994b440]::ty::self_ty_of_trait_impl_enabling_order_dep_trait_object_hack
  26:     0x7ff95034bab8 - rustc_query_impl[16b8175ba1dd8f83]::plumbing::query_key_hash_verify_all
  27:     0x7ff950bb786b - <rustc_middle[d84a46905b9833cf]::ty::Ty>::is_copy_modulo_regions
  28:     0x7ff9501d1cb6 - rustc_ty_utils[7a4117f0c994b440]::needs_drop::needs_drop_raw
  29:     0x7ff95033c93b - rustc_query_impl[16b8175ba1dd8f83]::plumbing::query_key_hash_verify_all
  30:     0x7ff95024b8b4 - rustc_ty_utils[7a4117f0c994b440]::ty::self_ty_of_trait_impl_enabling_order_dep_trait_object_hack
  31:     0x7ff95034be93 - rustc_query_impl[16b8175ba1dd8f83]::plumbing::query_key_hash_verify_all
  32:     0x7ff94fbe4582 - rustc_hir_analysis[f30f03e5312332c1]::collect::predicates_defined_on
  33:     0x7ff94fbd9438 - rustc_hir_analysis[f30f03e5312332c1]::collect::predicates_defined_on
  34:     0x7ff94f268549 - <rustc_hir_analysis[f30f03e5312332c1]::variance::variance_of_opaque::{closure#0}::OpaqueTypeLifetimeCollector as rustc_type_ir[aefdc4761e7ea19c]::visit::TypeVisitor<rustc_middle[d84a46905b9833cf]::ty::context::TyCtxt>>::visit_ty
  35:     0x7ff94f27ec9e - rustc_mir_transform[3a1eaf4008c3052b]::shim::make_shim
  36:     0x7ff94f4af817 - <dyn std[85dfe2848fbb0331]::io::Write as nu_ansi_term[494721e700deaf73]::write::AnyWrite>::write_str
  37:     0x7ff94f498cb3 - <dyn std[85dfe2848fbb0331]::io::Write as nu_ansi_term[494721e700deaf73]::write::AnyWrite>::write_str
  38:     0x7ff94f401391 - rustc_ty_utils[7a4117f0c994b440]::ty::adt_sized_constraint
  39:     0x7ff94f4c2b00 - rustc_query_impl[16b8175ba1dd8f83]::query_system
  40:     0x7ff950c68ddc - <rustc_middle[d84a46905b9833cf]::ty::context::TyCtxt>::instance_mir
  41:     0x7ff94fc285dd - rustc_mir_transform[3a1eaf4008c3052b]::inline::cycle::mir_inliner_callees
  42:     0x7ff94fc26a56 - rustc_mir_transform[3a1eaf4008c3052b]::inline::cycle::mir_inliner_callees
  43:     0x7ff94fc26afd - rustc_mir_transform[3a1eaf4008c3052b]::inline::cycle::mir_inliner_callees
  44:     0x7ff94f27c780 - <rustc_mir_transform[3a1eaf4008c3052b]::inline::Inline as rustc_middle[d84a46905b9833cf]::mir::MirPass>::run_pass
  45:     0x7ff94fbf9cdc - <rustc_mir_transform[3a1eaf4008c3052b]::simplify::SimplifyCfg as rustc_middle[d84a46905b9833cf]::mir::MirPass>::run_pass
  46:     0x7ff94fcb6145 - rustc_mir_transform[3a1eaf4008c3052b]::optimized_mir
  47:     0x7ff95033c7a0 - rustc_query_impl[16b8175ba1dd8f83]::plumbing::query_key_hash_verify_all
  48:     0x7ff95022a81a - rustc_ty_utils[7a4117f0c994b440]::ty::self_ty_of_trait_impl_enabling_order_dep_trait_object_hack
  49:     0x7ff950342b05 - rustc_query_impl[16b8175ba1dd8f83]::plumbing::query_key_hash_verify_all
  50:     0x7ff95203e0f2 - <cc[c04df6f83f42a58f]::AppleOs as core[8b3c6311f9756dee]::fmt::Debug>::fmt
  51:     0x7ff9508b6b75 - <rustc_metadata[d6eac6bb222208d8]::rmeta::encoder::EncodeContext as rustc_span[33560a3c1d01ec1a]::SpanEncoder>::encode_symbol
  52:     0x7ff94f69ebfa - rustc_metadata[d6eac6bb222208d8]::rmeta::encoder::encode_metadata
  53:     0x7ff94f6a6c88 - rustc_metadata[d6eac6bb222208d8]::fs::encode_and_write_metadata
  54:     0x7ff94cb0361a - <rustc_interface[7b147ced95828432]::queries::Queries>::codegen_and_build_linker
  55:     0x7ff94cab5c8b - _LNan_C
  56:     0x7ff94cab1c0f - _LNan_C
  57:     0x7ff94cabb239 - _LNan_C
  58:     0x7ff97cd7815d - alloc::boxed::impl$48::call_once
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\alloc\src\boxed.rs:2064
  59:     0x7ff97cd7815d - alloc::boxed::impl$48::call_once
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\alloc\src\boxed.rs:2064
  60:     0x7ff97cd7815d - std::sys::pal::windows::thread::impl$0::new::thread_start
                               at /rustc/4bc39f028d14c24b04dd17dc425432c6ec354536/library\std\src\sys\pal\windows\thread.rs:52
  61:     0x7ffa1779257d - BaseThreadInitThunk
  62:     0x7ffa1888af28 - RtlUserThreadStart


rustc version: 1.81.0-nightly (4bc39f028 2024-06-26)
platform: x86_64-pc-windows-msvc

query stack during panic:
#0 [evaluate_obligation] evaluating trait selection obligation `[core::mem::maybe_uninit::MaybeUninit<u8>; PAD2]: core::marker::Copy`
#1 [is_copy_raw] computing whether `[core::mem::maybe_uninit::MaybeUninit<u8>; PAD2]` is `Copy`
#2 [needs_drop_raw] computing whether `[core::mem::maybe_uninit::MaybeUninit<u8>; PAD2]` needs drop
#3 [mir_shims] generating MIR shim for `core::ptr::drop_in_place`
#4 [optimized_mir] optimizing MIR for `<impl at flexstr\src\lib.rs:207:1: 208:40>::drop`
end of query stack

[lqd]

Bisects to #125958, cc PR author @BoxyUwU -- ah but it's likely a duplicate of #126378 and so forth.

[Noratrieb]

this is stable and doesn't use effects, so it's probably different

[lqd]

@Nilstrieb I'm going from #126889 (comment)

[BoxyUwU]

I cannot reproduce this locally

edit: oh --release is required