ICE: gce: `unable to construct a constant value for the unevaluated constant UnevaluatedConst {..}`

[matthiaskrgr]

auto-reduced (treereduce-rust):

struct Checked<const F: fn(usize) -> bool>;

fn not_one(val: usize) -> bool {
    val != 1
}
const _: Checked<not_one> = Checked::<not_one>;

#![feature(generic_const_exprs)]

original:

struct Checked<const F: fn(usize) -> bool>;
//~^ ERROR function pointers as const generic parameters is forbidden
fn not_one(val: usize) -> bool { val != 1 }
const _: Checked<not_one> = Checked::<not_one>;
fn main() {}

Version information

rustc 1.76.0-nightly (4e3dc976e 2023-12-02)
binary: rustc
commit-hash: 4e3dc976e7876f59373ddc8ac176fe130636bcd1
commit-date: 2023-12-02
host: x86_64-unknown-linux-gnu
release: 1.76.0-nightly
LLVM version: 17.0.5

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zcrate-attr=feature(generic_const_exprs)

Program output

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:9
  |
1 | feature(generic_const_exprs)
  |         ^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
  = note: `#[warn(incomplete_features)]` on by default

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.gHur7OqFWv0M/rustc_testrunner_tmpdir_reporting.xiUdgEkFncd9/mvce.rs:6:48
  |
6 | const _: Checked<not_one> = Checked::<not_one>;
  |                                                ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.gHur7OqFWv0M/rustc_testrunner_tmpdir_reporting.xiUdgEkFncd9/mvce.rs`

error: using function pointers as const generic parameters is forbidden
 --> /tmp/icemaker_global_tempdir.gHur7OqFWv0M/rustc_testrunner_tmpdir_reporting.xiUdgEkFncd9/mvce.rs:1:25
  |
1 | struct Checked<const F: fn(usize) -> bool>;
  |                         ^^^^^^^^^^^^^^^^^
  |
  = note: the only supported types are integers, `bool` and `char`

error: internal compiler error: compiler/rustc_infer/src/infer/mod.rs:1579:17: unable to construct a constant value for the unevaluated constant UnevaluatedConst { def: DefId(0:8 ~ mvce[7b0d]::_::{constant#0}), args: [] }
 --> /tmp/icemaker_global_tempdir.gHur7OqFWv0M/rustc_testrunner_tmpdir_reporting.xiUdgEkFncd9/mvce.rs:6:18
  |
6 | const _: Checked<not_one> = Checked::<not_one>;
  |                  ^^^^^^^

thread 'rustc' panicked at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/compiler/rustc_errors/src/lib.rs:995:33:
Box<dyn Any>
stack backtrace:
   0:     0x7fda6dbd528c - std::backtrace_rs::backtrace::libunwind::trace::h6817338c94b27a3e
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7fda6dbd528c - std::backtrace_rs::backtrace::trace_unsynchronized::h0c6d9d3798c92386
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fda6dbd528c - std::sys_common::backtrace::_print_fmt::h834bcd6a65d45603
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7fda6dbd528c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h632d407336012a57
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7fda6dc282c0 - core::fmt::rt::Argument::fmt::h01e7093f49b63767
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/core/src/fmt/rt.rs:142:9
   5:     0x7fda6dc282c0 - core::fmt::write::h38701b4f0b2dfcb8
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/core/src/fmt/mod.rs:1120:17
   6:     0x7fda6dbc917f - std::io::Write::write_fmt::hb5f3f03cb3ca04d4
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/io/mod.rs:1810:15
   7:     0x7fda6dbd5074 - std::sys_common::backtrace::_print::hd3e5ed5a0b531af5
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7fda6dbd5074 - std::sys_common::backtrace::print::hb9af834fe41953f4
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7fda6dbd7d07 - std::panicking::default_hook::{{closure}}::h72d658988ab66f01
  10:     0x7fda6dbd7a6f - std::panicking::default_hook::h58213f9fd1d3009c
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/panicking.rs:292:9
  11:     0x7fda6a8f5cd0 - std[df2d6593d7194e63]::panicking::update_hook::<alloc[8a854d67183381ee]::boxed::Box<rustc_driver_impl[6cfe35843c87edd3]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7fda6dbd8448 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h7fd395d777c5491c
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/alloc/src/boxed.rs:2021:9
  13:     0x7fda6dbd8448 - std::panicking::rust_panic_with_hook::h98c8112ef43197a0
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/panicking.rs:783:13
  14:     0x7fda6ab7e564 - std[df2d6593d7194e63]::panicking::begin_panic::<rustc_errors[1ca61f24e5e0d229]::ExplicitBug>::{closure#0}
  15:     0x7fda6ab68386 - std[df2d6593d7194e63]::sys_common::backtrace::__rust_end_short_backtrace::<std[df2d6593d7194e63]::panicking::begin_panic<rustc_errors[1ca61f24e5e0d229]::ExplicitBug>::{closure#0}, !>
  16:     0x7fda6ab61426 - std[df2d6593d7194e63]::panicking::begin_panic::<rustc_errors[1ca61f24e5e0d229]::ExplicitBug>
  17:     0x7fda6ab51dae - <rustc_errors[1ca61f24e5e0d229]::HandlerInner>::span_bug::<rustc_span[9dcec85a30c01535]::span_encoding::Span, alloc[8a854d67183381ee]::string::String>
  18:     0x7fda6ab51708 - <rustc_errors[1ca61f24e5e0d229]::Handler>::span_bug::<rustc_span[9dcec85a30c01535]::span_encoding::Span, alloc[8a854d67183381ee]::string::String>
  19:     0x7fda6ab7ea9b - rustc_middle[decbaea72911547]::util::bug::opt_span_bug_fmt::<rustc_span[9dcec85a30c01535]::span_encoding::Span>::{closure#0}
  20:     0x7fda6ab7eaca - rustc_middle[decbaea72911547]::ty::context::tls::with_opt::<rustc_middle[decbaea72911547]::util::bug::opt_span_bug_fmt<rustc_span[9dcec85a30c01535]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7fda6ab683c8 - rustc_middle[decbaea72911547]::ty::context::tls::with_context_opt::<rustc_middle[decbaea72911547]::ty::context::tls::with_opt<rustc_middle[decbaea72911547]::util::bug::opt_span_bug_fmt<rustc_span[9dcec85a30c01535]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7fda6ab65284 - rustc_middle[decbaea72911547]::util::bug::span_bug_fmt::<rustc_span[9dcec85a30c01535]::span_encoding::Span>
  23:     0x7fda6abdb209 - <rustc_infer[d655d61eba052e30]::infer::InferCtxt>::try_const_eval_resolve
  24:     0x7fda6b455819 - <rustc_trait_selection[34dffbdf25348a0a]::traits::fulfill::FulfillProcessor as rustc_data_structures[47340807f7653890]::obligation_forest::ObligationProcessor>::process_obligation::{closure#1}
  25:     0x7fda68d08123 - <rustc_trait_selection[34dffbdf25348a0a]::traits::fulfill::FulfillProcessor as rustc_data_structures[47340807f7653890]::obligation_forest::ObligationProcessor>::process_obligation
  26:     0x7fda6bc11b84 - <rustc_data_structures[47340807f7653890]::obligation_forest::ObligationForest<rustc_trait_selection[34dffbdf25348a0a]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[34dffbdf25348a0a]::traits::fulfill::FulfillProcessor>
  27:     0x7fda6c5a9184 - <rustc_hir_typeck[9593c8bda2de2b24]::fn_ctxt::FnCtxt>::type_inference_fallback
  28:     0x7fda6bf138ad - rustc_hir_typeck[9593c8bda2de2b24]::typeck
  29:     0x7fda6bf12c7d - rustc_query_impl[ff29417da00622fc]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ff29417da00622fc]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[decbaea72911547]::query::erase::Erased<[u8; 8usize]>>
  30:     0x7fda6be50143 - rustc_query_system[9cd2f7f31604691c]::query::plumbing::try_execute_query::<rustc_query_impl[ff29417da00622fc]::DynamicConfig<rustc_query_system[9cd2f7f31604691c]::query::caches::VecCache<rustc_span[9dcec85a30c01535]::def_id::LocalDefId, rustc_middle[decbaea72911547]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[ff29417da00622fc]::plumbing::QueryCtxt, false>
  31:     0x7fda6be4fdd0 - rustc_query_impl[ff29417da00622fc]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  32:     0x7fda6c8d5570 - rustc_hir_analysis[da2a6e1063fa42ac]::check::check::check_mod_item_types
  33:     0x7fda6c8d4fb9 - rustc_query_impl[ff29417da00622fc]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ff29417da00622fc]::query_impl::check_mod_item_types::dynamic_query::{closure#2}::{closure#0}, rustc_middle[decbaea72911547]::query::erase::Erased<[u8; 0usize]>>
  34:     0x7fda6c5f65bb - rustc_query_system[9cd2f7f31604691c]::query::plumbing::try_execute_query::<rustc_query_impl[ff29417da00622fc]::DynamicConfig<rustc_query_system[9cd2f7f31604691c]::query::caches::DefaultCache<rustc_span[9dcec85a30c01535]::def_id::LocalModDefId, rustc_middle[decbaea72911547]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[ff29417da00622fc]::plumbing::QueryCtxt, false>
  35:     0x7fda6c5f5f97 - rustc_query_impl[ff29417da00622fc]::query_impl::check_mod_item_types::get_query_non_incr::__rust_end_short_backtrace
  36:     0x7fda6c624b23 - rustc_hir_analysis[da2a6e1063fa42ac]::check_crate
  37:     0x7fda6c782722 - rustc_interface[6c8aab51a4e81018]::passes::analysis
  38:     0x7fda6c78235d - rustc_query_impl[ff29417da00622fc]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ff29417da00622fc]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[decbaea72911547]::query::erase::Erased<[u8; 1usize]>>
  39:     0x7fda6cb65e80 - rustc_query_system[9cd2f7f31604691c]::query::plumbing::try_execute_query::<rustc_query_impl[ff29417da00622fc]::DynamicConfig<rustc_query_system[9cd2f7f31604691c]::query::caches::SingleCache<rustc_middle[decbaea72911547]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[ff29417da00622fc]::plumbing::QueryCtxt, false>
  40:     0x7fda6cb65c87 - rustc_query_impl[ff29417da00622fc]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  41:     0x7fda6cb74552 - rustc_interface[6c8aab51a4e81018]::interface::run_compiler::<core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>, rustc_driver_impl[6cfe35843c87edd3]::run_compiler::{closure#0}>::{closure#0}
  42:     0x7fda6cb67949 - std[df2d6593d7194e63]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[6c8aab51a4e81018]::util::run_in_thread_with_globals<rustc_interface[6c8aab51a4e81018]::util::run_in_thread_pool_with_globals<rustc_interface[6c8aab51a4e81018]::interface::run_compiler<core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>, rustc_driver_impl[6cfe35843c87edd3]::run_compiler::{closure#0}>::{closure#0}, core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>>::{closure#0}, core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>>
  43:     0x7fda6cb67773 - <<std[df2d6593d7194e63]::thread::Builder>::spawn_unchecked_<rustc_interface[6c8aab51a4e81018]::util::run_in_thread_with_globals<rustc_interface[6c8aab51a4e81018]::util::run_in_thread_pool_with_globals<rustc_interface[6c8aab51a4e81018]::interface::run_compiler<core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>, rustc_driver_impl[6cfe35843c87edd3]::run_compiler::{closure#0}>::{closure#0}, core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>>::{closure#0}, core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[50500588ec9d0052]::result::Result<(), rustc_span[9dcec85a30c01535]::ErrorGuaranteed>>::{closure#1} as core[50500588ec9d0052]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  44:     0x7fda6dbe22d5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h6bfd5ba6e023a698
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/alloc/src/boxed.rs:2007:9
  45:     0x7fda6dbe22d5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7da8003a07f4cffa
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/alloc/src/boxed.rs:2007:9
  46:     0x7fda6dbe22d5 - std::sys::unix::thread::Thread::new::thread_start::h64cf2021e889e721
                               at /rustc/4e3dc976e7876f59373ddc8ac176fe130636bcd1/library/std/src/sys/unix/thread.rs:108:17
  47:     0x7fda67aaa9eb - <unknown>
  48:     0x7fda67b2e7cc - <unknown>
  49:                0x0 - <unknown>

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 1.76.0-nightly (4e3dc976e 2023-12-02) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z crate-attr=feature(generic_const_exprs) -Z dump-mir-dir=dir

query stack during panic:
#0 [typeck] type-checking `_`
#1 [check_mod_item_types] checking item types in top-level module
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors; 1 warning emitted

For more information about this error, try `rustc --explain E0601`.

[sjwang05]

Reduced further:

#![feature(generic_const_exprs)]

struct Checked<const F: fn()>;

fn foo() {}
const _: Checked<foo> = Checked::<foo>;

searched nightlies: from nightly-2023-10-19 to nightly-2023-12-01
regressed nightly: nightly-2023-10-26
searched commit range: df871fb...ab5c841
regressed commit: ab5c841

bisected with cargo-bisect-rustc v0.6.7

Host triple: x86_64-pc-windows-msvc
Reproduce with:

cargo bisect-rustc

[matthiaskrgr]

caused by #117159