Normalization overflow detection in monomorphization is not sufficient

[adwinwhite]

As pointed out in the comment, my overflow check doesn't cover fields of types and probably other cases.
An improved solution needs to consider these missing cases while keeping the cost of check low.

This only causes ICE with Znext-solver, likely because the old solver can sometimes ignore the recursion limit.

Code

#![recursion_limit = "32"]

struct A;

trait HasAssoc {
    type Assoc;
}

impl HasAssoc for A {
    type Assoc = ();
}

struct S<T: HasAssoc>(T::Assoc);

impl<T: HasAssoc> HasAssoc for S<T> {
    type Assoc = T::Assoc;
}

// Wrap twice to make sure that projection depth grows faster than instance recursion depth.
fn wrap<T: HasAssoc>(a: T) -> S<S<T>> {
    panic!()
}

fn recurse<T: HasAssoc>(a: T) {
    if false {
        return;
    }

    recurse(wrap(a));
}

fn main() {
    recurse(A);
}

Meta

rustc --version --verbose:

rustc 1.91.0-dev
binary: rustc
commit-hash: unknown
commit-date: unknown
host: x86_64-unknown-linux-gnu
release: 1.91.0-dev
LLVM version: 21.1.0

Error output

[<output>](error: internal compiler error: compiler/rustc_middle/src/ty/instance.rs:577:21: failed to resolve instance for drop_in_place::<{type error}>)

Backtrace

thread 'rustc' panicked at compiler/rustc_middle/src/ty/instance.rs:577:21:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panicking.rs:769:5
   1: std::panic::panic_any::<rustc_errors::ExplicitBug>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panic.rs:260:5
   2: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
             at ./compiler/rustc_errors/src/diagnostic.rs:83:9
   3: <rustc_errors::diagnostic::Diag<rustc_errors::diagnostic::BugAbort>>::emit
             at ./compiler/rustc_errors/src/diagnostic.rs:1422:9
   4: <rustc_errors::DiagCtxtHandle>::span_bug::<rustc_span::span_encoding::Span, alloc::string::String>
             at ./compiler/rustc_errors/src/lib.rs:1235:48
   5: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
             at ./compiler/rustc_middle/src/util/bug.rs:38:54
   6: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
             at ./compiler/rustc_middle/src/ty/context/tls.rs:136:23
   7: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
             at ./compiler/rustc_middle/src/ty/context/tls.rs:79:18
   8: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>
             at ./compiler/rustc_middle/src/ty/context/tls.rs:134:5
   9: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>
             at ./compiler/rustc_middle/src/util/bug.rs:33:5
  10: rustc_middle::util::bug::span_bug_fmt::<rustc_span::span_encoding::Span>
             at ./compiler/rustc_middle/src/util/bug.rs:24:5
  11: <rustc_middle::ty::instance::Instance>::expect_resolve
             at ./compiler/rustc_middle/src/macros.rs:34:9
  12: <rustc_middle::ty::instance::Instance>::resolve_drop_in_place
             at ./compiler/rustc_middle/src/ty/instance.rs:735:9
  13: rustc_monomorphize::collector::visit_drop_use
             at ./compiler/rustc_monomorphize/src/collector.rs:895:20
  14: <rustc_monomorphize::collector::MirUsedCollector as rustc_middle::mir::visit::Visitor>::visit_terminator
             at ./compiler/rustc_monomorphize/src/collector.rs:826:17
  15: rustc_monomorphize::collector::collect_items_of_instance
             at ./compiler/rustc_monomorphize/src/collector.rs:1292:23
  16: rustc_monomorphize::collector::items_of_instance
             at ./compiler/rustc_monomorphize/src/collector.rs:1320:41
  17: rustc_query_impl::query_impl::items_of_instance::dynamic_query::{closure#2}::{closure#0}
             at ./compiler/rustc_query_impl/src/plumbing.rs:294:9
      [... omitted 22 frames ...]
  18: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefaultCache<(rustc_middle::ty::instance::Instance, rustc_middle::mir::mono::CollectionMode), rustc_middle::query::erase::Erased<[u8; 32]>>>
             at ./compiler/rustc_middle/src/query/plumbing.rs:182:17
  19: <rustc_middle::query::plumbing::TyCtxtAt>::items_of_instance
             at ./compiler/rustc_middle/src/query/plumbing.rs:475:31
  20: <rustc_middle::ty::context::TyCtxt>::items_of_instance
             at ./compiler/rustc_middle/src/query/plumbing.rs:466:35
  21: rustc_monomorphize::collector::collect_items_rec::{closure#2}
             at ./compiler/rustc_monomorphize/src/collector.rs:504:45
  22: stacker::maybe_grow::<(), rustc_monomorphize::collector::collect_items_rec::{closure#2}>
             at /home/adwin/.cargo/registry/src/mirrors.tuna.tsinghua.edu.cn-4dc01642fd091eda/stacker-0.1.21/src/lib.rs:57:9
  23: rustc_data_structures::stack::ensure_sufficient_stack::<(), rustc_monomorphize::collector::collect_items_rec::{closure#2}>
             at ./compiler/rustc_data_structures/src/stack.rs:21:5
  24: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:503:13
  25: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  26: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  27: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  28: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  29: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  30: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  31: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  32: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  33: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  34: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  35: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  36: rustc_monomorphize::collector::collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:604:13
  37: rustc_monomorphize::collector::collect_items_root
             at ./compiler/rustc_monomorphize/src/collector.rs:364:5
  38: rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}
             at ./compiler/rustc_monomorphize/src/collector.rs:1741:13
  39: rustc_data_structures::sync::parallel::par_for_each_in::<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}::{closure#0}
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:181:30
  40: <core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}::{closure#0}> as core::ops::function::FnOnce<()>>::call_once
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/core/src/panic/unwind_safe.rs:272:9
  41: std::panicking::catch_unwind::do_call::<core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}::{closure#0}>, ()>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panicking.rs:589:40
  42: std::panicking::catch_unwind::<(), core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}::{closure#0}>>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panicking.rs:552:19
  43: std::panic::catch_unwind::<core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}::{closure#0}>, ()>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panic.rs:359:14
  44: <rustc_data_structures::sync::parallel::ParallelGuard>::run::<(), rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}::{closure#0}>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:23:9
  45: rustc_data_structures::sync::parallel::par_for_each_in::<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:181:23
  46: core::iter::traits::iterator::Iterator::for_each::call::<rustc_middle::mir::mono::MonoItem, rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}>::{closure#0}
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/core/src/iter/traits/iterator.rs:824:29
  47: <alloc::vec::into_iter::IntoIter<rustc_middle::mir::mono::MonoItem> as core::iter::traits::iterator::Iterator>::fold::<(), core::iter::traits::iterator::Iterator::for_each::call<rustc_middle::mir::mono::MonoItem, rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}>::{closure#0}>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/alloc/src/vec/into_iter.rs:323:25
  48: <alloc::vec::into_iter::IntoIter<rustc_middle::mir::mono::MonoItem> as core::iter::traits::iterator::Iterator>::for_each::<rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/core/src/iter/traits/iterator.rs:827:14
  49: rustc_data_structures::sync::parallel::par_for_each_in::<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:180:27
  50: rustc_data_structures::sync::parallel::parallel_guard::<(), rustc_data_structures::sync::parallel::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:39:15
  51: rustc_data_structures::sync::parallel::par_for_each_in::<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:175:5
  52: rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}
             at ./compiler/rustc_monomorphize/src/collector.rs:1740:9
  53: <rustc_data_structures::profiling::VerboseTimingGuard>::run::<(), rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}>
             at ./compiler/rustc_data_structures/src/profiling.rs:844:9
  54: <rustc_session::session::Session>::time::<(), rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}>
             at ./compiler/rustc_session/src/utils.rs:16:50
  55: rustc_monomorphize::collector::collect_crate_mono_items
             at ./compiler/rustc_monomorphize/src/collector.rs:1739:14
  56: rustc_monomorphize::partitioning::collect_and_partition_mono_items
             at ./compiler/rustc_monomorphize/src/partitioning.rs:1131:30
  57: rustc_query_impl::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}
             at ./compiler/rustc_query_impl/src/plumbing.rs:294:9
      [... omitted 22 frames ...]
  58: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 40]>>>
             at ./compiler/rustc_middle/src/query/plumbing.rs:182:17
  59: <rustc_middle::query::plumbing::TyCtxtAt>::collect_and_partition_mono_items
             at ./compiler/rustc_middle/src/query/plumbing.rs:475:31
  60: <rustc_middle::ty::context::TyCtxt>::collect_and_partition_mono_items
             at ./compiler/rustc_middle/src/query/plumbing.rs:466:35
  61: rustc_codegen_ssa::base::codegen_crate::<rustc_codegen_llvm::LlvmCodegenBackend>
             at ./compiler/rustc_codegen_ssa/src/base.rs:669:13
  62: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
             at ./compiler/rustc_codegen_llvm/src/lib.rs:337:18
  63: rustc_interface::passes::start_codegen::{closure#0}
             at ./compiler/rustc_interface/src/passes.rs:1225:74
  64: <rustc_data_structures::profiling::VerboseTimingGuard>::run::<alloc::boxed::Box<dyn core::any::Any>, rustc_interface::passes::start_codegen::{closure#0}>
             at ./compiler/rustc_data_structures/src/profiling.rs:844:9
  65: <rustc_session::session::Session>::time::<alloc::boxed::Box<dyn core::any::Any>, rustc_interface::passes::start_codegen::{closure#0}>
             at ./compiler/rustc_session/src/utils.rs:16:50
  66: rustc_interface::passes::start_codegen
             at ./compiler/rustc_interface/src/passes.rs:1225:28
  67: <rustc_interface::queries::Linker>::codegen_and_build_linker
             at ./compiler/rustc_interface/src/queries.rs:32:43
  68: rustc_driver_impl::run_compiler::{closure#0}::{closure#2}
             at ./compiler/rustc_driver_impl/src/lib.rs:386:18
  69: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
             at ./compiler/rustc_interface/src/passes.rs:1006:27
  70: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}
             at ./compiler/rustc_middle/src/ty/context.rs:1546:37
  71: rustc_middle::ty::context::tls::enter_context::<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}
             at ./compiler/rustc_middle/src/ty/context/tls.rs:60:9
  72: <std::thread::local::LocalKey<core::cell::Cell<*const ()>>>::try_with::<rustc_middle::ty::context::tls::enter_context<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/thread/local.rs:315:12
  73: <std::thread::local::LocalKey<core::cell::Cell<*const ()>>>::with::<rustc_middle::ty::context::tls::enter_context<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/thread/local.rs:279:20
  74: rustc_middle::ty::context::tls::enter_context::<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>
             at ./compiler/rustc_middle/src/ty/context/tls.rs:57:9
  75: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
             at ./compiler/rustc_middle/src/ty/context.rs:1546:9
  76: <rustc_middle::ty::context::TyCtxt>::create_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}>
             at ./compiler/rustc_middle/src/ty/context.rs:1751:13
  77: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}
             at ./compiler/rustc_interface/src/passes.rs:973:9
  78: <rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/core/src/ops/function.rs:253:5
  79: <alloc::boxed::Box<dyn for<'a> core::ops::function::FnOnce<(&'a rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &'a std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt<'a>>, &'a rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena<'a>>, &'a rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena<'a>>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}), Output = core::option::Option<rustc_interface::queries::Linker>>> as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/alloc/src/boxed.rs:1971:9
  80: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
             at ./compiler/rustc_interface/src/passes.rs:1014:5
  81: rustc_driver_impl::run_compiler::{closure#0}
             at ./compiler/rustc_driver_impl/src/lib.rs:343:22
  82: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}
             at ./compiler/rustc_interface/src/interface.rs:525:80
  83: <core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}> as core::ops::function::FnOnce<()>>::call_once
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/core/src/panic/unwind_safe.rs:272:9
  84: std::panicking::catch_unwind::do_call::<core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}>, ()>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panicking.rs:589:40
  85: std::panicking::catch_unwind::<(), core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}>>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panicking.rs:552:19
  86: std::panic::catch_unwind::<core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}>, ()>
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panic.rs:359:14
  87: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
             at ./compiler/rustc_interface/src/interface.rs:525:23
  88: rustc_interface::util::run_in_thread_pool_with_globals::<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}
             at ./compiler/rustc_interface/src/util.rs:199:17
  89: rustc_interface::util::run_in_thread_with_globals::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}
             at ./compiler/rustc_interface/src/util.rs:153:24
  90: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}, ()>
             at /home/adwin/.cargo/registry/src/mirrors.tuna.tsinghua.edu.cn-4dc01642fd091eda/scoped-tls-1.0.1/src/lib.rs:137:9
  91: rustc_span::create_session_globals_then::<(), rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}>
             at ./compiler/rustc_span/src/lib.rs:146:21
  92: rustc_interface::util::run_in_thread_with_globals::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}
             at ./compiler/rustc_interface/src/util.rs:149:17
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 1.91.0-dev running on x86_64-unknown-linux-gnu

note: compiler flags: -Z next-solver

query stack during panic:
#0 [items_of_instance] collecting items used by `core::ptr::drop_in_place::<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<A>>>>>>>>>>>>>>>>>>> - shim(Some(S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<A>>>>>>>>>>>>>>>>>>))`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack

[RalfJung]

ISTM that predicting all normalizations codegen will do, and doing them in advance during mono item collection, is enaging in a game of whack-a-mole that we cannot win.

Would it make sense to instead change how we invoke these queries from codegen to emit a somewhat reasonable error instead of unwraping?

Cc @saethlin

[ben-kimock-ls]

I was not expecting the PR to be airtight, I was expecting the PR to make it less likely for users to run into these rare ICEs in practice without imposing significant compile-time overhead on the majority of users who will never see one of these ICEs and therefore are not benefiting from the additional compute.

Would it make sense to instead change how we invoke these queries from codegen to emit a somewhat reasonable error instead of unwraping?

These ICEs aren't caused by cg_ssa using .unwrap(). Only one of the fixed ICEs was related to a call to Instance::expect_resolve, in part of the MirUsedCollector code. The necessary changes would not be in codegen, they would be (as best I can tell) all over the compiler.

These ICEs mostly look like assertion failures elsewhere in the compiler, so my best guess is that various parts of the compiler have been written on the assumption that someone else is going to halt compilation under some circumstance, which is what the PR in question does.

[saethlin]

🤦 Oh I answered this from my Work laptop. I'll just let that sit rather than try to paper over it now.

[adwinwhite]

Now that I think about it, returning error from places where overflow happens is indeed too large a change.
For the code above, the error originates from here:

rust/compiler/rustc_mir_transform/src/elaborate_drop.rs

Lines 514 to 519 in 28fad95

	let field_ty = match tcx.try_normalize_erasing_regions(
	self.elaborator.typing_env(),
	field.ty(tcx, args),
	) {
	Ok(t) => t,
	Err(_) => Ty::new_error(

We need change its enclosing function signature all the way to instance_mir, if it's even possible.

[RalfJung]

Emitting an error does not require returning one.

[adwinwhite]

Without proper span info, we can't provide helpful diagnostic.

Either we pass the info in or propagate the error out. Both are too invasive.

Explanation on why we need the span of the starting item to provide helpful diagnostic.