ICE -Zpolymorphize=on "collection encountered polymorphic constant: Unevaluated(UnevaluatedConst"

[matthiaskrgr]

Code

src/test/ui/issues/issue-39292.rs

// run-pass
// Regression test for issue #39292. The object vtable was being
// incorrectly left with a null pointer.

trait Foo<T> {
    fn print<'a>(&'a self) where T: 'a { println!("foo"); }
}

impl<'a> Foo<&'a ()> for () { }

trait Bar: for<'a> Foo<&'a ()> { }

impl Bar for () {}

fn main() {
    (&() as &dyn Bar).print(); // Segfault
}

Meta

rustc --version --verbose:

rustc 1.67.0-nightly (32e613bba 2022-12-02)
binary: rustc
commit-hash: 32e613bbaafee1bcabba48a2257b838f8d1c03d3
commit-date: 2022-12-02
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

Error output

rustc src/test/ui/issues/issue-39292.rs -Zpolymorphize=on

<output>

Backtrace

error: internal compiler error: compiler/rustc_monomorphize/src/collector.rs:786:54: collection encountered polymorphic constant: Unevaluated(UnevaluatedConst { def: WithOptConstParam { did: DefId(0:5 ~ issue_39292[a2ad]::Foo::print), const_param_did: None }, substs: [(), T, ReErased], promoted: Some(promoted[1]) }, &[&str; 1])
 --> src/test/ui/issues/issue-39292.rs:6:51
  |
6 |     fn print<'a>(&'a self) where T: 'a { println!("foo"); }
  |                                                   ^^^^^

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/compiler/rustc_errors/src/lib.rs:972:33
stack backtrace:
   0:     0x7ff11c464a5a - std::backtrace_rs::backtrace::libunwind::trace::h445f1a380ebe24fa
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7ff11c464a5a - std::backtrace_rs::backtrace::trace_unsynchronized::h8c542444dc84bbad
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7ff11c464a5a - std::sys_common::backtrace::_print_fmt::hd1e3793b0f95c644
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7ff11c464a5a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h515025d5c2825d78
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7ff11c8efe4e - core::fmt::write::hfd15a46634ae3152
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/core/src/fmt/mod.rs:1208:17
   5:     0x7ff11c458cc5 - std::io::Write::write_fmt::h74b2e38eb2a622bf
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/io/mod.rs:1682:15
   6:     0x7ff11c464825 - std::sys_common::backtrace::_print::hd2af8aafbe5d4e4d
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7ff11c464825 - std::sys_common::backtrace::print::hc83e0ce2c452dd90
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7ff11c466baf - std::panicking::default_hook::{{closure}}::h6fa5498814662258
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/panicking.rs:267:22
   9:     0x7ff11c4668eb - std::panicking::default_hook::h27c5cc64dbc8482d
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/panicking.rs:286:9
  10:     0x7ff11b6bdf24 - rustc_driver[1a6385c1c72d16e7]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7ff11c4673ad - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h555d7d9f22ed347d
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/alloc/src/boxed.rs:2032:9
  12:     0x7ff11c4673ad - std::panicking::rust_panic_with_hook::hf0b4a17e8b00f779
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/panicking.rs:692:13
  13:     0x7ff11bd9e991 - std[79527836cf90b5dd]::panicking::begin_panic::<rustc_errors[643e9caaba05b420]::ExplicitBug>::{closure#0}
  14:     0x7ff11bd9e376 - std[79527836cf90b5dd]::sys_common::backtrace::__rust_end_short_backtrace::<std[79527836cf90b5dd]::panicking::begin_panic<rustc_errors[643e9caaba05b420]::ExplicitBug>::{closure#0}, !>
  15:     0x7ff11bd95d56 - std[79527836cf90b5dd]::panicking::begin_panic::<rustc_errors[643e9caaba05b420]::ExplicitBug>
  16:     0x7ff11bdaab56 - std[79527836cf90b5dd]::panic::panic_any::<rustc_errors[643e9caaba05b420]::ExplicitBug>
  17:     0x7ff11bda9af9 - <rustc_errors[643e9caaba05b420]::HandlerInner>::span_bug::<rustc_span[c03eaf4ea18165a3]::span_encoding::Span, &alloc[976f33e9556b75e2]::string::String>
  18:     0x7ff11bda9780 - <rustc_errors[643e9caaba05b420]::Handler>::span_bug::<rustc_span[c03eaf4ea18165a3]::span_encoding::Span, &alloc[976f33e9556b75e2]::string::String>
  19:     0x7ff11bda7211 - rustc_middle[19d5e5a4d6179ade]::ty::context::tls::with_context_opt::<rustc_middle[19d5e5a4d6179ade]::ty::context::tls::with_opt<rustc_middle[19d5e5a4d6179ade]::util::bug::opt_span_bug_fmt<rustc_span[c03eaf4ea18165a3]::span_encoding::Span>::{closure#0}, ()>::{closure#0}, ()>
  20:     0x7ff11bda70c6 - rustc_middle[19d5e5a4d6179ade]::util::bug::opt_span_bug_fmt::<rustc_span[c03eaf4ea18165a3]::span_encoding::Span>
  21:     0x7ff11bda7084 - rustc_middle[19d5e5a4d6179ade]::util::bug::span_bug_fmt::<rustc_span[c03eaf4ea18165a3]::span_encoding::Span>
  22:     0x7ff1195f9335 - rustc_monomorphize[f852be8325467616]::collector::collect_neighbours
  23:     0x7ff1195e92e9 - rustc_monomorphize[f852be8325467616]::collector::collect_items_rec
  24:     0x7ff1195e9754 - rustc_monomorphize[f852be8325467616]::collector::collect_items_rec
  25:     0x7ff11aa5e7b5 - <rustc_session[2f16cc1ca0f45371]::session::Session>::time::<(), rustc_monomorphize[f852be8325467616]::collector::collect_crate_mono_items::{closure#1}>
  26:     0x7ff11aa5e2d4 - rustc_monomorphize[f852be8325467616]::collector::collect_crate_mono_items
  27:     0x7ff11aa5d6e3 - rustc_monomorphize[f852be8325467616]::partitioning::collect_and_partition_mono_items
  28:     0x7ff11ae33a00 - rustc_query_system[c29954e9c418d3e1]::query::plumbing::try_execute_query::<rustc_query_impl[81623dbe8f24b13f]::plumbing::QueryCtxt, rustc_query_system[c29954e9c418d3e1]::query::caches::DefaultCache<(), (&std[79527836cf90b5dd]::collections::hash::set::HashSet<rustc_span[c03eaf4ea18165a3]::def_id::DefId, core[7075224b64f80aa]::hash::BuildHasherDefault<rustc_hash[7698cfb367caca01]::FxHasher>>, &[rustc_middle[19d5e5a4d6179ade]::mir::mono::CodegenUnit])>>
  29:     0x7ff11ae336c4 - rustc_query_system[c29954e9c418d3e1]::query::plumbing::get_query::<rustc_query_impl[81623dbe8f24b13f]::queries::collect_and_partition_mono_items, rustc_query_impl[81623dbe8f24b13f]::plumbing::QueryCtxt>
  30:     0x7ff11ae335fe - <rustc_query_impl[81623dbe8f24b13f]::Queries as rustc_middle[19d5e5a4d6179ade]::ty::query::QueryEngine>::collect_and_partition_mono_items
  31:     0x7ff11ab215fb - rustc_codegen_ssa[234fb96bead002ba]::base::codegen_crate::<rustc_codegen_llvm[7650bcf584e55ba6]::LlvmCodegenBackend>
  32:     0x7ff11ab213a9 - <rustc_codegen_llvm[7650bcf584e55ba6]::LlvmCodegenBackend as rustc_codegen_ssa[234fb96bead002ba]::traits::backend::CodegenBackend>::codegen_crate
  33:     0x7ff11a7f4941 - <rustc_session[2f16cc1ca0f45371]::session::Session>::time::<alloc[976f33e9556b75e2]::boxed::Box<dyn core[7075224b64f80aa]::any::Any>, rustc_interface[ee8495dca531fc0c]::passes::start_codegen::{closure#0}>
  34:     0x7ff11a7f4435 - rustc_interface[ee8495dca531fc0c]::passes::start_codegen
  35:     0x7ff11a7efb1d - <rustc_interface[ee8495dca531fc0c]::passes::QueryContext>::enter::<<rustc_interface[ee8495dca531fc0c]::queries::Queries>::ongoing_codegen::{closure#0}::{closure#0}, core[7075224b64f80aa]::result::Result<alloc[976f33e9556b75e2]::boxed::Box<dyn core[7075224b64f80aa]::any::Any>, rustc_errors[643e9caaba05b420]::ErrorGuaranteed>>
  36:     0x7ff11a7ed334 - <rustc_interface[ee8495dca531fc0c]::queries::Queries>::ongoing_codegen
  37:     0x7ff11a7ec501 - <rustc_interface[ee8495dca531fc0c]::interface::Compiler>::enter::<rustc_driver[1a6385c1c72d16e7]::run_compiler::{closure#1}::{closure#2}, core[7075224b64f80aa]::result::Result<core[7075224b64f80aa]::option::Option<rustc_interface[ee8495dca531fc0c]::queries::Linker>, rustc_errors[643e9caaba05b420]::ErrorGuaranteed>>
  38:     0x7ff11a7e74e8 - rustc_span[c03eaf4ea18165a3]::with_source_map::<core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>, rustc_interface[ee8495dca531fc0c]::interface::run_compiler<core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>, rustc_driver[1a6385c1c72d16e7]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
  39:     0x7ff11a7e6fd5 - <scoped_tls[6605aed902b0fb11]::ScopedKey<rustc_span[c03eaf4ea18165a3]::SessionGlobals>>::set::<rustc_interface[ee8495dca531fc0c]::interface::run_compiler<core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>, rustc_driver[1a6385c1c72d16e7]::run_compiler::{closure#1}>::{closure#0}, core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>>
  40:     0x7ff11a7e65c2 - std[79527836cf90b5dd]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[ee8495dca531fc0c]::util::run_in_thread_pool_with_globals<rustc_interface[ee8495dca531fc0c]::interface::run_compiler<core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>, rustc_driver[1a6385c1c72d16e7]::run_compiler::{closure#1}>::{closure#0}, core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>>
  41:     0x7ff11af6b8e8 - <<std[79527836cf90b5dd]::thread::Builder>::spawn_unchecked_<rustc_interface[ee8495dca531fc0c]::util::run_in_thread_pool_with_globals<rustc_interface[ee8495dca531fc0c]::interface::run_compiler<core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>, rustc_driver[1a6385c1c72d16e7]::run_compiler::{closure#1}>::{closure#0}, core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[7075224b64f80aa]::result::Result<(), rustc_errors[643e9caaba05b420]::ErrorGuaranteed>>::{closure#1} as core[7075224b64f80aa]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  42:     0x7ff11c46e5e3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hb948150b9fd67a86
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/alloc/src/boxed.rs:2000:9
  43:     0x7ff11c46e5e3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h2f842213b427eb19
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/alloc/src/boxed.rs:2000:9
  44:     0x7ff11c46e5e3 - std::sys::unix::thread::Thread::new::thread_start::h2adb6f1223042fb8
                               at /rustc/32e613bbaafee1bcabba48a2257b838f8d1c03d3/library/std/src/sys/unix/thread.rs:108:17
  45:     0x7ff1182658fd - <unknown>
  46:     0x7ff1182e7a60 - <unknown>
  47:                0x0 - <unknown>

note: 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: rustc 1.67.0-nightly (32e613bba 2022-12-02) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z polymorphize=on

query stack during panic:
#0 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to previous error

[matthiaskrgr]

searched toolchains 95a992a68694d8bf3959bd2c0ac27ce9e9208b59 through 98ad6a5519651af36e246c0335c964dd52c554ba
Regression in c524c7d
#98588 cc @b-naber

[b-naber]

@rustbot claim

[matthiaskrgr]

Another example

fn pass_to_ptr_call<T>(f: fn(T), x: T) {
    f(x);
}

trait TrackedTrait {
    fn trait_tracked_unit_default(_: ()) {
        let location = std::panic::Location::caller();
        assert_eq!(location.file(), file!());
    }
}

impl TrackedTrait for () {}

fn main() {
    pass_to_ptr_call(<() as TrackedTrait>::trait_tracked_unit_default, ());
}

[chenyukang]

@b-naber
whether it's Ok to report the error:

error: unexpected polymorphic constant
  --> tests/ui/higher-ranked/trait-bounds/issue-39292.rs:10:18
   |
10 |         println!("foo");
   |                  ^^^^^

My Pr #114985 take care the error.

[cushionbadak]

Similar case but additional -Zprint-mono-items=eager option required to produce ICE:

Code

pub struct S();

pub trait X {
    fn unused3(var: i32) {
        println!("{}", var);
    }
}

impl X for S {}

fn main() {}

Command

rustc -Zprint-mono-items=eager -Zpolymorphize=on

Meta

rustc 1.79.0-nightly (c9f8f3438 2024-03-27)
binary: rustc
commit-hash: c9f8f3438a8134a413aa5d4903e0196e44e37bbc
commit-date: 2024-03-27
host: x86_64-apple-darwin
release: 1.79.0-nightly
LLVM version: 18.1.2

Output

Output

error: internal compiler error: compiler/rustc_monomorphize/src/collector.rs:820:50: collection encountered polymorphic constant: Unevaluated(UnevaluatedConst { def: DefId(0:6 ~ reduced_3C760D49C[7e62]::X::unused3), args: [Self/#0], promoted: Some(promoted[0]) }, &'{erased} [&'{erased} str; 2_usize])
 --> 0327/reduced_3C760D49C.rs:5:18
  |
5 |         println!("{}", var);
  |                  ^^^^

thread 'rustc' panicked at compiler/rustc_monomorphize/src/collector.rs:820:50:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: <rustc_errors::DiagCtxt>::span_bug::<rustc_span::span_encoding::Span, 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::span_bug_fmt::<rustc_span::span_encoding::Span>
   7: <rustc_monomorphize::collector::MirUsedCollector>::eval_constant
   8: <rustc_monomorphize::collector::MirUsedCollector as rustc_middle::mir::visit::Visitor>::visit_operand
   9: rustc_monomorphize::collector::collect_items_rec::{closure#0}
  10: rustc_monomorphize::collector::collect_items_rec
  11: rustc_monomorphize::partitioning::collect_and_partition_mono_items
      [... omitted 2 frames ...]
  12: rustc_codegen_ssa::base::codegen_crate::<rustc_codegen_llvm::LlvmCodegenBackend>
  13: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  14: rustc_interface::passes::start_codegen
  15: <rustc_interface::queries::Queries>::codegen_and_build_linker
  16: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}
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 `/Volumes/T7/workspace/placeholder_rustexec/rustc-ice-2024-03-28T04_33_10-57934.txt` to your bug report

note: compiler flags: -Z print-mono-items=eager -Z polymorphize=on

query stack during panic:
#0 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to 1 previous error