ICE unexpected unsized tail: std::alloc::Global

[Thomasdezeeuw]

Sorry in advance, this is going to be a pretty poor bug report as I don't have much time to look into this at the moment, but I did want to create an issue for it.

Code

I can't share the code at the moment, nor do I have time to create a minimal repo. I can say a number of nightly features are involved:

• async_fn_in_trait
• async_iterator
• const_mut_refs
• const_option
• const_weak_new
• doc_auto_cfg
• doc_cfg_hide
• extract_if
• impl_trait_in_assoc_type
• io_slice_advance
• is_sorted
• maybe_uninit_array_assume_init
• maybe_uninit_uninit_array
• maybe_uninit_write_slice
• never_type
• new_uninit
• noop_waker
• ptr_metadata
• stmt_expr_attributes
• waker_getters

I found that I can reproduce it in public code as well: https://github.com/Thomasdezeeuw/heph/tree/82faf4987d0ac1b07b7e81c481d0047b1f3dee5d/http. Running cargo test --doc fails, specifically this example: https://github.com/Thomasdezeeuw/heph/blob/82faf4987d0ac1b07b7e81c481d0047b1f3dee5d/http/src/server.rs#L28-L143.

Meta

rustc --version --verbose:

rustc 1.73.0-nightly (db7ff98a7 2023-07-31)
binary: rustc
commit-hash: db7ff98a72f3e742b641f9cb16d0e8c285e87e9b
commit-date: 2023-07-31
host: x86_64-unknown-linux-gnu
release: 1.73.0-nightly
LLVM version: 16.0.5

Error output

error: internal compiler error: compiler/rustc_monomorphize/src/collector.rs:1023:22: unexpected unsized tail: std::alloc::Global

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/compiler/rustc_errors/src/lib.rs:1645:9
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::HandlerInner>::bug::<alloc::string::String>
   2: <rustc_errors::Handler>::bug::<alloc::string::String>
   3: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   4: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   5: 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}, !>
   6: rustc_middle::util::bug::bug_fmt
   7: rustc_monomorphize::collector::find_vtable_types_for_unsizing
   8: rustc_monomorphize::collector::collect_used_items
   9: rustc_monomorphize::collector::collect_items_rec
  10: rustc_monomorphize::collector::collect_items_rec
  11: rustc_monomorphize::collector::collect_items_rec
  12: rustc_monomorphize::collector::collect_items_rec
  13: rustc_monomorphize::collector::collect_items_rec
  14: rustc_monomorphize::collector::collect_items_rec
  15: rustc_monomorphize::collector::collect_items_rec
  16: rustc_monomorphize::collector::collect_items_rec
  17: rustc_monomorphize::collector::collect_items_rec
  18: rustc_data_structures::sync::par_for_each_in::<alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>
  19: <rustc_session::session::Session>::time::<(), rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}>
  20: rustc_monomorphize::collector::collect_crate_mono_items
  21: rustc_monomorphize::partitioning::collect_and_partition_mono_items
      [... omitted 2 frames ...]
  22: rustc_codegen_ssa::base::codegen_crate::<rustc_codegen_llvm::LlvmCodegenBackend>
  23: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  24: <rustc_session::session::Session>::time::<alloc::boxed::Box<dyn core::any::Any>, rustc_interface::passes::start_codegen::{closure#0}>
  25: rustc_interface::passes::start_codegen
  26: <rustc_middle::ty::context::GlobalCtxt>::enter::<<rustc_interface::queries::Queries>::ongoing_codegen::{closure#0}, core::result::Result<alloc::boxed::Box<dyn core::any::Any>, rustc_span::ErrorGuaranteed>>
  27: <rustc_interface::interface::Compiler>::enter::<rustc_driver_impl::run_compiler::{closure#1}::{closure#2}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
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 attach the file at `rustc-ice-2023-08-01T12:27:21.49188995Z-26207.txt` to your bug report

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

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

query stack during panic:
#0 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack

Backtrace

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/compiler/rustc_errors/src/lib.rs:1645:9
stack backtrace:
   0:     0x7f89895634bc - std::backtrace_rs::backtrace::libunwind::trace::h00560e9152510f67
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f89895634bc - std::backtrace_rs::backtrace::trace_unsynchronized::h0f27c3665dd0a867
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f89895634bc - std::sys_common::backtrace::_print_fmt::h5dba0ff3e06fa698
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f89895634bc - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h4debeea1996f535b
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f89895c9bac - core::fmt::rt::Argument::fmt::h1e53d9bbf5a265dd
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/core/src/fmt/rt.rs:138:9
   5:     0x7f89895c9bac - core::fmt::write::hcb86202702aeaf68
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/core/src/fmt/mod.rs:1094:21
   6:     0x7f8989555a2e - std::io::Write::write_fmt::h53395fbe87a19ae1
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/io/mod.rs:1714:15
   7:     0x7f89895632a5 - std::sys_common::backtrace::_print::h63c494f55c85c02e
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f89895632a5 - std::sys_common::backtrace::print::h0d84953923cd4383
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f89895663fa - std::panicking::panic_hook_with_disk_dump::{{closure}}::h0ded106e3e100970
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/panicking.rs:278:22
  10:     0x7f8989565f66 - std::panicking::panic_hook_with_disk_dump::h80545efc2b457190
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/panicking.rs:305:9
  11:     0x7f898c80a2e9 - rustc_driver_impl[953ac255d00f3c7f]::install_ice_hook::{closure#0}
  12:     0x7f8989566ca0 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h005d394de554c94e
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/alloc/src/boxed.rs:2021:9
  13:     0x7f8989566ca0 - std::panicking::rust_panic_with_hook::ha35d072680b6716b
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/panicking.rs:733:13
  14:     0x7f898cd7c711 - std[cfe24ee53075a1e5]::panicking::begin_panic::<rustc_errors[b1a6789dfd2ebe34]::ExplicitBug>::{closure#0}
  15:     0x7f898cd79cc6 - std[cfe24ee53075a1e5]::sys_common::backtrace::__rust_end_short_backtrace::<std[cfe24ee53075a1e5]::panicking::begin_panic<rustc_errors[b1a6789dfd2ebe34]::ExplicitBug>::{closure#0}, !>
  16:     0x7f898cdc1776 - std[cfe24ee53075a1e5]::panicking::begin_panic::<rustc_errors[b1a6789dfd2ebe34]::ExplicitBug>
  17:     0x7f898cd83594 - <rustc_errors[b1a6789dfd2ebe34]::HandlerInner>::bug::<alloc[9d71a00e6f43b08]::string::String>
  18:     0x7f898cd83426 - <rustc_errors[b1a6789dfd2ebe34]::Handler>::bug::<alloc[9d71a00e6f43b08]::string::String>
  19:     0x7f898ce10cec - rustc_middle[23eac342ec155d27]::util::bug::opt_span_bug_fmt::<rustc_span[c85fb125fe1c027]::span_encoding::Span>::{closure#0}
  20:     0x7f898ce0faea - rustc_middle[23eac342ec155d27]::ty::context::tls::with_opt::<rustc_middle[23eac342ec155d27]::util::bug::opt_span_bug_fmt<rustc_span[c85fb125fe1c027]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7f898ce0fab8 - rustc_middle[23eac342ec155d27]::ty::context::tls::with_context_opt::<rustc_middle[23eac342ec155d27]::ty::context::tls::with_opt<rustc_middle[23eac342ec155d27]::util::bug::opt_span_bug_fmt<rustc_span[c85fb125fe1c027]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7f898b112bc0 - rustc_middle[23eac342ec155d27]::util::bug::bug_fmt
  23:     0x7f898a8906a9 - rustc_monomorphize[be8a90b76663c72f]::collector::find_vtable_types_for_unsizing
  24:     0x7f898a86ba0f - rustc_monomorphize[be8a90b76663c72f]::collector::collect_used_items
  25:     0x7f898a864d7b - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  26:     0x7f898a8656dc - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  27:     0x7f898a8656dc - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  28:     0x7f898a8656dc - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  29:     0x7f898a8656dc - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  30:     0x7f898a8656dc - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  31:     0x7f898a8656dc - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  32:     0x7f898a8656dc - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  33:     0x7f898a8656dc - rustc_monomorphize[be8a90b76663c72f]::collector::collect_items_rec
  34:     0x7f898bdc5ea0 - rustc_data_structures[1e82c702e6afba98]::sync::par_for_each_in::<alloc[9d71a00e6f43b08]::vec::Vec<rustc_middle[23eac342ec155d27]::mir::mono::MonoItem>, rustc_monomorphize[be8a90b76663c72f]::collector::collect_crate_mono_items::{closure#1}::{closure#0}>
  35:     0x7f898bdc5799 - <rustc_session[1b335dd3cc3c5820]::session::Session>::time::<(), rustc_monomorphize[be8a90b76663c72f]::collector::collect_crate_mono_items::{closure#1}>
  36:     0x7f898bdc53f8 - rustc_monomorphize[be8a90b76663c72f]::collector::collect_crate_mono_items
  37:     0x7f898bdc39d7 - rustc_monomorphize[be8a90b76663c72f]::partitioning::collect_and_partition_mono_items
  38:     0x7f898be148c9 - rustc_query_impl[c1c3c70d39a20423]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c1c3c70d39a20423]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle[23eac342ec155d27]::query::erase::Erased<[u8; 24usize]>>
  39:     0x7f898be1489b - <rustc_query_impl[c1c3c70d39a20423]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2} as core[24a2ba61524efef7]::ops::function::FnOnce<(rustc_middle[23eac342ec155d27]::ty::context::TyCtxt, ())>>::call_once
  40:     0x7f898bffa155 - rustc_query_system[85489b7677581133]::query::plumbing::try_execute_query::<rustc_query_impl[c1c3c70d39a20423]::DynamicConfig<rustc_query_system[85489b7677581133]::query::caches::SingleCache<rustc_middle[23eac342ec155d27]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[c1c3c70d39a20423]::plumbing::QueryCtxt, true>
  41:     0x7f898c1a1e5d - rustc_query_impl[c1c3c70d39a20423]::query_impl::collect_and_partition_mono_items::get_query_incr::__rust_end_short_backtrace
  42:     0x7f898b95c5e6 - rustc_codegen_ssa[1e93ac4b57e61c57]::base::codegen_crate::<rustc_codegen_llvm[fbffa82a3d5a30ab]::LlvmCodegenBackend>
  43:     0x7f898b95c3cb - <rustc_codegen_llvm[fbffa82a3d5a30ab]::LlvmCodegenBackend as rustc_codegen_ssa[1e93ac4b57e61c57]::traits::backend::CodegenBackend>::codegen_crate
  44:     0x7f898ba8cf02 - <rustc_session[1b335dd3cc3c5820]::session::Session>::time::<alloc[9d71a00e6f43b08]::boxed::Box<dyn core[24a2ba61524efef7]::any::Any>, rustc_interface[22a5bdce7fd6e981]::passes::start_codegen::{closure#0}>
  45:     0x7f898ba8ca4b - rustc_interface[22a5bdce7fd6e981]::passes::start_codegen
  46:     0x7f898ba86ffa - <rustc_middle[23eac342ec155d27]::ty::context::GlobalCtxt>::enter::<<rustc_interface[22a5bdce7fd6e981]::queries::Queries>::ongoing_codegen::{closure#0}, core[24a2ba61524efef7]::result::Result<alloc[9d71a00e6f43b08]::boxed::Box<dyn core[24a2ba61524efef7]::any::Any>, rustc_span[c85fb125fe1c027]::ErrorGuaranteed>>
  47:     0x7f898ba86033 - <rustc_interface[22a5bdce7fd6e981]::interface::Compiler>::enter::<rustc_driver_impl[953ac255d00f3c7f]::run_compiler::{closure#1}::{closure#2}, core[24a2ba61524efef7]::result::Result<core[24a2ba61524efef7]::option::Option<rustc_interface[22a5bdce7fd6e981]::queries::Linker>, rustc_span[c85fb125fe1c027]::ErrorGuaranteed>>
  48:     0x7f898ba7f0a8 - std[cfe24ee53075a1e5]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[22a5bdce7fd6e981]::util::run_in_thread_pool_with_globals<rustc_interface[22a5bdce7fd6e981]::interface::run_compiler<core[24a2ba61524efef7]::result::Result<(), rustc_span[c85fb125fe1c027]::ErrorGuaranteed>, rustc_driver_impl[953ac255d00f3c7f]::run_compiler::{closure#1}>::{closure#0}, core[24a2ba61524efef7]::result::Result<(), rustc_span[c85fb125fe1c027]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[24a2ba61524efef7]::result::Result<(), rustc_span[c85fb125fe1c027]::ErrorGuaranteed>>
  49:     0x7f898ba7e82e - <<std[cfe24ee53075a1e5]::thread::Builder>::spawn_unchecked_<rustc_interface[22a5bdce7fd6e981]::util::run_in_thread_pool_with_globals<rustc_interface[22a5bdce7fd6e981]::interface::run_compiler<core[24a2ba61524efef7]::result::Result<(), rustc_span[c85fb125fe1c027]::ErrorGuaranteed>, rustc_driver_impl[953ac255d00f3c7f]::run_compiler::{closure#1}>::{closure#0}, core[24a2ba61524efef7]::result::Result<(), rustc_span[c85fb125fe1c027]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[24a2ba61524efef7]::result::Result<(), rustc_span[c85fb125fe1c027]::ErrorGuaranteed>>::{closure#1} as core[24a2ba61524efef7]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  50:     0x7f8989571445 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h021e65daf5fb4ee0
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/alloc/src/boxed.rs:2007:9
  51:     0x7f8989571445 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7dda744b120f2954
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/alloc/src/boxed.rs:2007:9
  52:     0x7f8989571445 - std::sys::unix::thread::Thread::new::thread_start::hcffeb1067f9b6dfb
                               at /rustc/db7ff98a72f3e742b641f9cb16d0e8c285e87e9b/library/std/src/sys/unix/thread.rs:108:17
  53:     0x7f898930244b - <unknown>
  54:     0x7f8989385e40 - <unknown>
  55:                0x0 - <unknown>


rustc version: 1.73.0-nightly (db7ff98a7 2023-07-31)
platform: x86_64-unknown-linux-gnu

query stack during panic:
#0 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack

[Luk-ESC]

Minimzed to:

#![feature(impl_trait_in_assoc_type)]

use std::future::Future;

fn main() {
    RuntimeRef::spawn_local(actor_fn(http_actor));
}

async fn http_actor() {
    async fn respond(body: impl Body) {
        body.write_message().await;
    }

    respond(&()).await;
}

trait Body {
    type WriteFuture: Future;

    fn write_message(self) -> Self::WriteFuture;
}

impl Body for &'static () {
    type WriteFuture = impl Future<Output = ()>;

    fn write_message(self) -> Self::WriteFuture {
        async {}
    }
}

trait NewActor {
    type RuntimeAccess;
}

fn actor_fn<T, A>(_d: T) -> (T, A) {
    loop {}
}

impl<F: FnMut() -> A, A> NewActor for (F, A) {
    type RuntimeAccess = RuntimeRef;
}
struct RuntimeRef(Vec<()>);

impl RuntimeRef {
    fn spawn_local<NA: NewActor<RuntimeAccess = RuntimeRef>>(_f: NA) {
        struct ActorFuture<NA: NewActor>(NA::RuntimeAccess);
        (ActorFuture::<NA>(RuntimeRef(vec![])), _f);
    }
}

This now errors with "unexpected unsized tail: usize", but i think that should be alright (?). If someone really needs the original error, I might have it lying around somewhere.

[kpreid]

Triage: The above minimal code now compiles successfully on 1.77.0-nightly (2023-12-24 bf8716f), so this issue may have been fixed or may need a new MCVE.

[Thomasdezeeuw]

Triage: The above minimal code now compiles successfully on 1.77.0-nightly (2023-12-24 bf8716f), so this issue may have been fixed or may need a new MCVE.

Can confirm that this has been resolved. Do we want to keep this open to add a regression test? Otherwise I'm fine with closing.

[lqd]

If the issue is fixed in heph and your private code, then let's use the MCVE above to add a regression test.

@rustbot label -E-needs-mcve +E-needs-test