ICE：rustc panicked at compiler\rustc_mir_transform\src\validate.rs:1560:30

The code is generated by a fuzzer and reduced manually and I tried to search similar issue but got no results.
My apologies if this is a repetitive question

Code

//-Z validate-mir
fn A() -> impl {
    while A() {}
    loop {}
}
fn main() {}

Error output

error: at least one trait must be specified
    |
177 | fn A() -> impl {
    |           ^^^^

error: internal compiler error: compiler\rustc_mir_transform\src\validate.rs:1560:30: unhandled type: Alias(Opaque, AliasTy { args: [], def_id: DefId(0:4 ~ test[354f]::A::{opaque#0}), .. })

Backtrace

thread 'rustc' panicked at compiler\rustc_mir_transform\src\validate.rs:1560:30:
Box<dyn Any>
stack backtrace:
   0:     0x7ffd45bbd382 - std::backtrace_rs::backtrace::win64::trace
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\..\..\backtrace\src\backtrace\win64.rs:85
   1:     0x7ffd45bbd382 - std::backtrace_rs::backtrace::trace_unsynchronized
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\..\..\backtrace\src\backtrace\mod.rs:66  
   2:     0x7ffd45bbd382 - std::sys::backtrace::_print_fmt
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\sys\backtrace.rs:66
   3:     0x7ffd45bbd382 - std::sys::backtrace::impl$0::print::impl$0::fmt
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\sys\backtrace.rs:39
   4:     0x7ffd45befb4b - core::fmt::rt::Argument::fmt
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\core\src\fmt\rt.rs:181
   5:     0x7ffd45befb4b - core::fmt::write
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\core\src\fmt\mod.rs:1446
   6:     0x7ffd45bb34d7 - std::io::default_write_fmt
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\io\mod.rs:639
   7:     0x7ffd45bb34d7 - std::io::Write::write_fmt<std::sys::stdio::windows::Stderr>
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\io\mod.rs:1914
   8:     0x7ffd45bbd1c5 - std::sys::backtrace::BacktraceLock::print
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\sys\backtrace.rs:42
   9:     0x7ffd45bc2e1a - std::panicking::default_hook::closure$0
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\panicking.rs:300   
  10:     0x7ffd45bc2bb0 - std::panicking::default_hook
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\panicking.rs:327   
  11:     0x7ffd472e08d9 - core[f111e4a7ef605334]::slice::sort::unstable::heapsort::heapsort::<((rustc_lint_defs[bc50006dd5ee5521]::Level, &str), usize), <((rustc_lint_defs[bc50006dd5ee5521]::Level, &str), usize) as core[f111e4a7ef605334]::cmp::PartialOrd>::lt>
  12:     0x7ffd45bc3aae - std::panicking::rust_panic_with_hook
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\panicking.rs:841
  13:     0x7ffd48b737d3 - RINvNtNtNtNtCskHcYUSqe9DI_4core5slice4sort6stable9quicksort9quicksortTjRNtNtCsgBC9fiOAFQn_12rustc_errors7snippet10AnnotationENCINvMNtCsamXvYCKHpPZ_5alloc5sliceSB15_11sort_by_keyTINtNtBa_3cmp7ReversejEbENCNCNvMs5_NtB1c_7emitterNtB3o_12HumanEmitter18render_s
  14:     0x7ffd48b66e79 - std[aad7a0f80ff4ecfa]::sys::backtrace::__rust_end_short_backtrace::<std[aad7a0f80ff4ecfa]::panicking::begin_panic<rustc_errors[c16db17667fbb355]::ExplicitBug>::{closure#0}, !>
  15:     0x7ffd48b61d6f - std[aad7a0f80ff4ecfa]::panicking::begin_panic::<rustc_errors[c16db17667fbb355]::ExplicitBug>
  16:     0x7ffd48b80a55 - <rustc_errors[c16db17667fbb355]::diagnostic::BugAbort as rustc_errors[c16db17667fbb355]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  17:     0x7ffd48ac6949 - rustc_middle[22e762101f903b8f]::util::bug::span_bug_fmt::<rustc_span[590cee7fbea9b74]::span_encoding::Span>
  18:     0x7ffd48a9928d - <rustc_middle[22e762101f903b8f]::ty::consts::Const>::walk
  19:     0x7ffd48a99056 - <rustc_middle[22e762101f903b8f]::ty::consts::Const>::walk
  20:     0x7ffd48ac6842 - rustc_middle[22e762101f903b8f]::util::bug::bug_fmt
  21:     0x7ffd4613bea4 - <rustc_mir_transform[57db05d0ea21705e]::validate::Validator as rustc_mir_transform[57db05d0ea21705e]::pass_manager::MirPass>::run_pass
  22:     0x7ffd4612c743 - <rustc_mir_transform[57db05d0ea21705e]::validate::Validator as rustc_mir_transform[57db05d0ea21705e]::pass_manager::MirPass>::run_pass
  23:     0x7ffd47a21437 - <rustc_mir_transform[57db05d0ea21705e]::post_drop_elaboration::CheckLiveDrops as rustc_mir_transform[57db05d0ea21705e]::pass_manager::MirLint>::run_lint
  24:     0x7ffd46058cee - rustc_mir_transform[57db05d0ea21705e]::mir_built
  25:     0x7ffd46b0eb8b - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  26:     0x7ffd46a3bed4 - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtCs4XH7gZc0tJl_21rustc_data_structures9vec_cache8VecCacheNtNtCskbO0hp1YYUt_9rustc_hir6hir_id7OwnerIdINtNtNtCs2ZN7GrsimL3_12rus
  27:     0x7ffd46b12c62 - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  28:     0x7ffd46049429 - rustc_mir_transform[57db05d0ea21705e]::ffi_unwind_calls::has_ffi_unwind_calls
  29:     0x7ffd46b0da2b - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  30:     0x7ffd46a4762e - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtCs4XH7gZc0tJl_21rustc_data_structures9vec_cache8VecCacheNtNtCstCNOwk8FZ8_10rustc_span6def_id10LocalDefIdINtNtNtCs2ZN7GrsimL3_
  31:     0x7ffd46b1d840 - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  32:     0x7ffd4605a491 - rustc_mir_transform[57db05d0ea21705e]::mir_promoted
  33:     0x7ffd46b0ca09 - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  34:     0x7ffd46a43c21 - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtCs4XH7gZc0tJl_21rustc_data_structures9vec_cache8VecCacheNtNtCstCNOwk8FZ8_10rustc_span6def_id10LocalDefIdINtNtNtCs2ZN7GrsimL3_
  35:     0x7ffd46b13212 - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  36:     0x7ffd46309918 - rustc_borrowck[f94e5613ded3b3c6]::mir_borrowck
  37:     0x7ffd46b0c98b - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  38:     0x7ffd46a3bed4 - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtCs4XH7gZc0tJl_21rustc_data_structures9vec_cache8VecCacheNtNtCskbO0hp1YYUt_9rustc_hir6hir_id7OwnerIdINtNtNtCs2ZN7GrsimL3_12rus
  39:     0x7ffd46b17412 - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  40:     0x7ffd454015ca - <rustc_hir_analysis[7fbad424b7a1f69a]::collect::resolve_bound_vars::is_late_bound_map::AllCollector as rustc_hir[eb2b9f614ea32def]::intravisit::Visitor>::visit_opaque_ty
  41:     0x7ffd4540198a - <rustc_hir_analysis[7fbad424b7a1f69a]::collect::resolve_bound_vars::is_late_bound_map::AllCollector as rustc_hir[eb2b9f614ea32def]::intravisit::Visitor>::visit_opaque_ty
  42:     0x7ffd45739deb - <alloc[78ca1fd804cb7045]::sync::Arc<rustc_session[dc649e9a0adc57bd]::config::OutputFilenames>>::drop_slow
  43:     0x7ffd469d6e05 - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtB4_6caches10DefIdCacheINtNtNtCs2ZN7GrsimL3_12rustc_middle5query5erase6ErasedAhj8_EEKb0_KB3r_KB3r_ENtNtB1f_8plumbing9QueryCtxt
  44:     0x7ffd457434a4 - rustc_query_impl[d652848cb58f7d7f]::query_system
  45:     0x7ffd45f2cf8d - <rustc_hir_analysis[7fbad424b7a1f69a]::collect::resolve_bound_vars::is_late_bound_map::ConstrainedCollector as rustc_hir[eb2b9f614ea32def]::intravisit::Visitor>::visit_ty
  46:     0x7ffd46b0ea00 - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  47:     0x7ffd469d6e05 - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtB4_6caches10DefIdCacheINtNtNtCs2ZN7GrsimL3_12rustc_middle5query5erase6ErasedAhj8_EEKb0_KB3r_KB3r_ENtNtB1f_8plumbing9QueryCtxt
  48:     0x7ffd46b10a66 - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  49:     0x7ffd453dde2c - rustc_hir_analysis[7fbad424b7a1f69a]::check::check::check_abi_fn_ptr
  50:     0x7ffd45ef4244 - rustc_hir_analysis[7fbad424b7a1f69a]::check::wfcheck::check_well_formed
  51:     0x7ffd46b0d48b - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  52:     0x7ffd46a478ce - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtCs4XH7gZc0tJl_21rustc_data_structures9vec_cache8VecCacheNtNtCstCNOwk8FZ8_10rustc_span6def_id10LocalDefIdINtNtNtCs2ZN7GrsimL3_
  53:     0x7ffd46b1de65 - rustc_query_impl[d652848cb58f7d7f]::plumbing::query_key_hash_verify_all
  54:     0x7ffd45f04965 - rustc_hir_analysis[7fbad424b7a1f69a]::check::wfcheck::check_mod_type_wf
  55:     0x7ffd4573af0b - <alloc[78ca1fd804cb7045]::sync::Arc<rustc_session[dc649e9a0adc57bd]::config::OutputFilenames>>::drop_slow
  56:     0x7ffd45687636 - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtB4_6caches12DefaultCacheNtNtCstCNOwk8FZ8_10rustc_span6def_id13LocalModDefIdINtNtNtCs2ZN7GrsimL3_12rustc_middle5query5erase6Er
  57:     0x7ffd4574f630 - rustc_query_impl[d652848cb58f7d7f]::query_system
  58:     0x7ffd45f4f8fe - rustc_hir_analysis[7fbad424b7a1f69a]::check_crate
  59:     0x7ffd45c271d3 - <rustc_interface[2753224ec3fdb3d8]::passes::LintStoreExpandImpl as rustc_expand[e6543defcfeccacc]::base::LintStoreExpand>::pre_expansion_lint
  60:     0x7ffd4252da87 - rustc_interface[2753224ec3fdb3d8]::passes::analysis
  61:     0x7ffd4573dc9a - <alloc[78ca1fd804cb7045]::sync::Arc<rustc_session[dc649e9a0adc57bd]::config::OutputFilenames>>::drop_slow
  62:     0x7ffd456466ba - RINvNtNtCs1OtVrNO53sG_18rustc_query_system5query8plumbing17try_execute_queryINtCsioPD87bJVb7_16rustc_query_impl13DynamicConfigINtNtB4_6caches11SingleCacheINtNtNtCs2ZN7GrsimL3_12rustc_middle5query5erase6ErasedAhj0_EEKb0_KB3s_KB3s_ENtNtB1f_8plumbing9QueryCtx
  63:     0x7ffd457442c3 - rustc_query_impl[d652848cb58f7d7f]::query_system
  64:     0x7ffd424eecb5 - std[aad7a0f80ff4ecfa]::sys::backtrace::__rust_begin_short_backtrace::<<std[aad7a0f80ff4ecfa]::thread::Builder>::spawn_unchecked_<ctrlc[d1d1c403957100d4]::set_handler_inner<rustc_driver_impl[66120e850aa3d048]::install_ctrlc_handler::{closure#0}>::{closure#0}, ()>::{closure#1}::{closure#0}::{closure#0}, ()>
  65:     0x7ffd424e8f13 - std[aad7a0f80ff4ecfa]::sys::backtrace::__rust_begin_short_backtrace::<<std[aad7a0f80ff4ecfa]::thread::Builder>::spawn_unchecked_<ctrlc[d1d1c403957100d4]::set_handler_inner<rustc_driver_impl[66120e850aa3d048]::install_ctrlc_handler::{closure#0}>::{closure#0}, ()>::{closure#1}::{closure#0}::{closure#0}, ()>
  66:     0x7ffd424e479f - RINvNtNtCseFo9rzt8nG0_3std3sys9backtrace28___rust_begin_short_backtraceNCNCINvNtCs3nk84nPWrZA_15rustc_interface4util26run_in_thread_with_globalsNCINvB1e_31run_in_thread_pool_with_globalsNCINvNtB1g_9interface12run_compileruNCNvCs8LjMsns72Ye_17rustc_driver_i
  67:     0x7ffd424f3010 - std[aad7a0f80ff4ecfa]::sys::backtrace::__rust_begin_short_backtrace::<<std[aad7a0f80ff4ecfa]::thread::Builder>::spawn_unchecked_<ctrlc[d1d1c403957100d4]::set_handler_inner<rustc_driver_impl[66120e850aa3d048]::install_ctrlc_handler::{closure#0}>::{closure#0}, ()>::{closure#1}::{closure#0}::{closure#0}, ()>
  68:     0x7ffd45bc7e1d - alloc::boxed::impl$28::call_once
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\alloc\src\boxed.rs:1966
  69:     0x7ffd45bc7e1d - alloc::boxed::impl$28::call_once
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\alloc\src\boxed.rs:1966
  70:     0x7ffd45bc7e1d - std::sys::pal::windows::thread::impl$0::new::thread_start
                               at /rustc/50aa04180709189a03dde5fd1c05751b2625ed37/library\std\src\sys\pal\windows\thread.rs:56
  71:     0x7ffe20097374 - BaseThreadInitThunk
  72:     0x7ffe2057cc91 - RtlUserThreadStart

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: compiler flags: -Z validate-mir

query stack during panic:
#0 [mir_built] building MIR for `A`
#1 [has_ffi_unwind_calls] checking if `A` contains FFI-unwind calls
... and 7 other queries... use `env RUST_BACKTRACE=1` to see the full query stack
error: aborting due to 2 previous errors

looks like a duplicate of #126680 I think

One interesting thing is that when I specified the specific type constraints for the program and added the main function, it also spawned ICE at stable rustc 1.86.0

fn A() -> impl Clone{
    while A() {}
    loop {}
}
fn main() {}

rustc --version --verbose:

rustc 1.86.0 (05f9846f8 2025-03-31)
binary: rustc
commit-hash: 05f9846f893b09a1be1fc8560e33fc3c815cfecb
commit-date: 2025-03-31
host: x86_64-pc-windows-msvc
release: 1.86.0
LLVM version: 19.1.7

error: internal compiler error: broken MIR in DefId(0:3 ~ test[97a0]::A) (Terminator { source_info: SourceInfo { span: .\test.rs:2:11: 2:14 (#0), scope: scope[0] }, kind: switchInt(move _3) -> [0: bb5, otherwise: bb4] }): bad SwitchInt discr ty Alias(Opaque, AliasTy { args: [], def_id: DefId(0:4 ~ test[97a0]::A::{opaque#0}), .. })
  |
2 |     while A() {}
  |           ^^^
  |
note: delayed at compiler\rustc_borrowck\src\type_check\mod.rs:1051:21 - disabled backtrace
  |
2 |     while A() {}
  |           ^^^

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 1.86.0 (05f9846f8 2025-03-31) running on x86_64-pc-windows-msvc

query stack during panic:
end of query stack

It seems like #126680 is fixed now(in rustc-2025-07-26) but this doesn't.

(However, glacier2 classifies both 126680.rs and 140850.rs as fixed issue, though this one still ICEs with rustc -Zvalidate-mir)

Rollup merge of rust-lang#163806 - lcnr:crashes-migration-cont, r=lqd

Unrolled build for #163806 in rollup 163957

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ICE：rustc panicked at compiler\rustc_mir_transform\src\validate.rs:1560:30 #140850

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ICE：rustc panicked at compiler\rustc_mir_transform\src\validate.rs:1560:30 #140850

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matthiaskrgr commented on May 9, 2025

sososopy commented on May 10, 2025

cushionbadak commented on Jul 27, 2025

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