[ICE]: `shouldn't have created a ValTree for pattern_type!(u32 is 0..=999999999)`

[matthiaskrgr]

auto-reduced (treereduce-rust):

//@compile-flags: --edition=2024
#![feature(generic_const_args)]
use core::time::Duration;
const TOO_LARGE_FACTOR: f64 = Duration::MAX.as_nanos() as f64;

original:

#![feature(generic_const_args, min_generic_const_args)]
use core::time::Duration;
const TOO_LARGE_FACTOR: f64 = Duration::MAX.as_nanos() as f64;
fn main() {}

Version information

rustc 1.100.0-nightly (0f819a160 2026-09-05)
binary: rustc
commit-hash: 0f819a1602c3814642aa63799b43772b7bb456e8
commit-date: 2026-09-05
host: x86_64-unknown-linux-gnu
release: 1.100.0-nightly
LLVM version: 23.1.1

Possibly related line of code:

rust/compiler/rustc_const_eval/src/const_eval/valtrees.rs

Lines 473 to 485 in 0f819a1

	ecx.write_discriminant(variant_idx, place).unwrap();
	}
	debug!("dump of place after writing discriminant:");
	dump_place(ecx, place);
	}
	_ => bug!("shouldn't have created a ValTree for {:?}", ty),
	}
	}
	fn dump_place<'tcx>(ecx: &CompileTimeInterpCx<'tcx>, place: &MPlaceTy<'tcx>) {
	trace!("{:?}", ecx.dump_place(&PlaceTy::from(place.clone())));
	}

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --edition=2024

Program output

error: `generic_const_args` requires `min_generic_const_args` to be enabled
 --> /tmp/icemaker_global_tempdir.qlZXSZnOsYFO/rustc_testrunner_tmpdir_reporting.7Ot4pTl3LGuS/mvce.rs:1:12
  |
1 | #![feature(generic_const_args)]
  |            ^^^^^^^^^^^^^^^^^^
  |
  = help: enable all of these features

warning: the feature `generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.qlZXSZnOsYFO/rustc_testrunner_tmpdir_reporting.7Ot4pTl3LGuS/mvce.rs:1:12
  |
1 | #![feature(generic_const_args)]
  |            ^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #151972 <https://github.com/rust-lang/rust/issues/151972> for more information
  = note: `#[warn(incomplete_features)]` on by default

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.qlZXSZnOsYFO/rustc_testrunner_tmpdir_reporting.7Ot4pTl3LGuS/mvce.rs:3:63
  |
3 | const TOO_LARGE_FACTOR: f64 = Duration::MAX.as_nanos() as f64;
  |                                                               ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.qlZXSZnOsYFO/rustc_testrunner_tmpdir_reporting.7Ot4pTl3LGuS/mvce.rs`

error: internal compiler error: /rustc-dev/0f819a1602c3814642aa63799b43772b7bb456e8/compiler/rustc_const_eval/src/const_eval/valtrees.rs:479:14: shouldn't have created a ValTree for pattern_type!(u32 is 0..=999999999)


thread 'rustc' (820812) panicked at /rustc-dev/0f819a1602c3814642aa63799b43772b7bb456e8/compiler/rustc_const_eval/src/const_eval/valtrees.rs:479:14:
Box<dyn Any>
stack backtrace:
   0:     0x7f0c06cc54e6 - <<std[739b682464b2cb4f]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[d997ca8b291862e0]::fmt::Display>::fmt
   1:     0x7f0c0740ba4f - core[d997ca8b291862e0]::fmt::write
   2:     0x7f0c06cda5cc - <std[739b682464b2cb4f]::sys::stdio::unix::Stderr as core[d997ca8b291862e0]::io::write::Write>::write_fmt
   3:     0x7f0c06c97d8a - std[739b682464b2cb4f]::panicking::default_hook::{closure#0}
   4:     0x7f0c06cb97e3 - std[739b682464b2cb4f]::panicking::default_hook
   5:     0x7f0c05c0943f - std[739b682464b2cb4f]::panicking::update_hook::<alloc[cfd194cf86e92e23]::boxed::Box<rustc_driver_impl[4b133f65db23c9ab]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f0c06cb9c82 - std[739b682464b2cb4f]::panicking::panic_with_hook
   7:     0x7f0c05c37ca4 - std[739b682464b2cb4f]::panicking::begin_panic::<rustc_errors[d96522ad5d42be40]::ExplicitBug>::{closure#0}
   8:     0x7f0c05c3077e - std[739b682464b2cb4f]::sys::backtrace::__rust_end_short_backtrace::<std[739b682464b2cb4f]::panicking::begin_panic<rustc_errors[d96522ad5d42be40]::ExplicitBug>::{closure#0}, !>
   9:     0x7f0c05c2e81e - std[739b682464b2cb4f]::panicking::begin_panic::<rustc_errors[d96522ad5d42be40]::ExplicitBug>
  10:     0x7f0c05c43571 - <rustc_errors[d96522ad5d42be40]::diagnostic::BugAbort as rustc_errors[d96522ad5d42be40]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7f0c061e6659 - rustc_middle[d333a51e0864de4]::util::bug::opt_span_bug_fmt::<rustc_span[e9d5129d271bd047]::span_encoding::Span>::{closure#0}
  12:     0x7f0c061e6a52 - rustc_middle[d333a51e0864de4]::ty::context::tls::with_opt::<rustc_middle[d333a51e0864de4]::util::bug::opt_span_bug_fmt<rustc_span[e9d5129d271bd047]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  13:     0x7f0c061d17b0 - rustc_middle[d333a51e0864de4]::ty::context::tls::with_context_opt::<rustc_middle[d333a51e0864de4]::ty::context::tls::with_opt<rustc_middle[d333a51e0864de4]::util::bug::opt_span_bug_fmt<rustc_span[e9d5129d271bd047]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  14:     0x7f0c02ea1fa4 - rustc_middle[d333a51e0864de4]::util::bug::bug_fmt
  15:     0x7f0c07b3ecce - rustc_const_eval[e1978c296a42a7e9]::const_eval::valtrees::valtree_into_mplace
  16:     0x7f0c07b3ea8a - rustc_const_eval[e1978c296a42a7e9]::const_eval::valtrees::valtree_into_mplace
  17:     0x7f0c07b3ea8a - rustc_const_eval[e1978c296a42a7e9]::const_eval::valtrees::valtree_into_mplace
  18:     0x7f0c0466634e - rustc_const_eval[e1978c296a42a7e9]::const_eval::valtrees::valtree_to_const_value
  19:     0x7f0c08009c2b - <rustc_const_eval[e1978c296a42a7e9]::provide::{closure#1} as core[d997ca8b291862e0]::ops::function::FnOnce<(rustc_middle[d333a51e0864de4]::ty::context::TyCtxt, rustc_middle[d333a51e0864de4]::ty::consts::valtree::Value)>>::call_once
  20:     0x7f0c08009bdc - rustc_query_impl[483fff85713b0294]::query_vtables::valtree_to_const_val::invoke_provider_fn::__rust_begin_short_backtrace
  21:     0x7f0c08009454 - rustc_query_impl[483fff85713b0294]::execution::try_execute_query::<rustc_middle[d333a51e0864de4]::query::caches::DefaultCache<rustc_middle[d333a51e0864de4]::ty::consts::valtree::Value, rustc_middle[d333a51e0864de4]::query::erase::ErasedData<[u8; 24usize]>>, false>
  22:     0x7f0c0800917e - rustc_query_impl[483fff85713b0294]::query_vtables::valtree_to_const_val::execute_query_non_incr::__rust_end_short_backtrace
  23:     0x7f0c07bf9c02 - <rustc_middle[d333a51e0864de4]::mir::consts::Const>::eval
  24:     0x7f0c07bf90f1 - <rustc_const_eval[e1978c296a42a7e9]::interpret::eval_context::InterpCx<rustc_const_eval[e1978c296a42a7e9]::const_eval::machine::CompileTimeMachine>>::push_stack_frame_raw
  25:     0x7f0c04b77db0 - rustc_const_eval[e1978c296a42a7e9]::const_eval::eval_queries::eval_to_allocation_raw_provider
  26:     0x7f0c07426196 - rustc_query_impl[483fff85713b0294]::query_vtables::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
  27:     0x7f0c08374ba6 - rustc_query_impl[483fff85713b0294]::execution::try_execute_query::<rustc_middle[d333a51e0864de4]::query::caches::DefaultCache<rustc_middle[d333a51e0864de4]::ty::PseudoCanonicalInput<rustc_middle[d333a51e0864de4]::mir::interpret::GlobalId>, rustc_middle[d333a51e0864de4]::query::erase::ErasedData<[u8; 24usize]>>, false>
  28:     0x7f0c08374127 - rustc_query_impl[483fff85713b0294]::query_vtables::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
  29:     0x7f0c08370bbd - rustc_const_eval[e1978c296a42a7e9]::const_eval::eval_queries::eval_to_const_value_raw_provider
  30:     0x7f0c08370834 - rustc_query_impl[483fff85713b0294]::query_vtables::eval_to_const_value_raw::invoke_provider_fn::__rust_begin_short_backtrace
  31:     0x7f0c083745d5 - rustc_query_impl[483fff85713b0294]::execution::try_execute_query::<rustc_middle[d333a51e0864de4]::query::caches::DefaultCache<rustc_middle[d333a51e0864de4]::ty::PseudoCanonicalInput<rustc_middle[d333a51e0864de4]::mir::interpret::GlobalId>, rustc_middle[d333a51e0864de4]::query::erase::ErasedData<[u8; 24usize]>>, false>
  32:     0x7f0c0837416d - rustc_query_impl[483fff85713b0294]::query_vtables::eval_to_const_value_raw::execute_query_non_incr::__rust_end_short_backtrace
  33:     0x7f0c083716f2 - rustc_const_eval[e1978c296a42a7e9]::const_eval::eval_queries::eval_to_const_value_raw_provider
  34:     0x7f0c08370834 - rustc_query_impl[483fff85713b0294]::query_vtables::eval_to_const_value_raw::invoke_provider_fn::__rust_begin_short_backtrace
  35:     0x7f0c083745d5 - rustc_query_impl[483fff85713b0294]::execution::try_execute_query::<rustc_middle[d333a51e0864de4]::query::caches::DefaultCache<rustc_middle[d333a51e0864de4]::ty::PseudoCanonicalInput<rustc_middle[d333a51e0864de4]::mir::interpret::GlobalId>, rustc_middle[d333a51e0864de4]::query::erase::ErasedData<[u8; 24usize]>>, false>
  36:     0x7f0c0837416d - rustc_query_impl[483fff85713b0294]::query_vtables::eval_to_const_value_raw::execute_query_non_incr::__rust_end_short_backtrace
  37:     0x7f0c07bb52a5 - <rustc_middle[d333a51e0864de4]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis[b601ba688d898738]::check_crate::{closure#1}>::{closure#0}
  38:     0x7f0c07bb3f36 - rustc_hir_analysis[b601ba688d898738]::check_crate
  39:     0x7f0c07ac4a88 - rustc_interface[69481172a0b187c3]::passes::analysis
  40:     0x7f0c085dc9ca - rustc_query_impl[483fff85713b0294]::execution::try_execute_query::<rustc_middle[d333a51e0864de4]::query::caches::SingleCache<rustc_middle[d333a51e0864de4]::query::erase::ErasedData<[u8; 0usize]>>, false>
  41:     0x7f0c085dc753 - rustc_query_impl[483fff85713b0294]::query_vtables::analysis::execute_query_non_incr::__rust_end_short_backtrace
  42:     0x7f0c0879eae4 - rustc_interface[69481172a0b187c3]::interface::run_compiler::<(), rustc_driver_impl[4b133f65db23c9ab]::run_compiler::{closure#0}>::{closure#2}
  43:     0x7f0c08803164 - std[739b682464b2cb4f]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[69481172a0b187c3]::util::run_in_thread_with_globals<rustc_interface[69481172a0b187c3]::util::run_in_thread_pool_with_globals<rustc_interface[69481172a0b187c3]::interface::run_compiler<(), rustc_driver_impl[4b133f65db23c9ab]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  44:     0x7f0c08802f0b - <std[739b682464b2cb4f]::thread::lifecycle::spawn_unchecked<rustc_interface[69481172a0b187c3]::util::run_in_thread_with_globals<rustc_interface[69481172a0b187c3]::util::run_in_thread_pool_with_globals<rustc_interface[69481172a0b187c3]::interface::run_compiler<(), rustc_driver_impl[4b133f65db23c9ab]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[d997ca8b291862e0]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  45:     0x7f0c08800947 - <std[739b682464b2cb4f]::sys::thread::unix::Thread>::new::thread_start
  46:     0x7f0c018980a2 - <unknown>
  47:     0x7f0c0192080c - <unknown>
  48:                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: please make sure that you have updated to the latest nightly

note: rustc 1.100.0-nightly (0f819a160 2026-09-05) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z dump-mir-dir=dir

query stack during panic:
#0 [valtree_to_const_val] converting type-level constant value to MIR constant value
#1 [eval_to_allocation_raw] const-evaluating + checking `TOO_LARGE_FACTOR`
#2 [eval_to_const_value_raw] simplifying constant for the type system `TOO_LARGE_FACTOR`
#3 [eval_to_const_value_raw] simplifying constant for the type system `TOO_LARGE_FACTOR`
#4 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 3 previous errors; 1 warning emitted

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

@rustbot label +F-generic_const_args +F-min_generic_const_args

[matthiaskrgr]

probably similar:

#![feature(macroless_const_item_generic_const_args)]
#![feature(generic_const_args)]
const A: &'static [u8; 0x2468_ACF1_3579_BDFF_DB97_530E_CA86_420] = b"1";
static B: u8 = A[0];

fn main() {
    println!("{B}");
}

thread 'rustc' (891149) panicked at /rustc-dev/0fc141305da7a8a222f65aef1f1acc739c46282b/compiler/rustc_const_eval/src/const_eval/valtrees.rs:394:77:
called `Result::unwrap()` on an `Err` value: InvalidProgram(Layout(SizeOverflow([u8; 18282773015276577824_usize])))
stack backtrace:
   0:     0x7f4d8a637456 - <<std[71a467343b18a2c1]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[11918ecc8322c3ee]::fmt::Display>::fmt
   1:     0x7f4d8ac09ccf - core[11918ecc8322c3ee]::fmt::write

[crumblingstatue]

Another repro (added per request)

#![feature(min_generic_const_args, generic_const_args)]

use std::time::{Duration, Instant};

#[derive(Debug)]
pub struct Timer {
    init_point: Instant,
    duration: Duration,
}

impl Timer {
    pub fn set(duration: Duration) -> Self {
        Self {
            init_point: Instant::now(),
            duration,
        }
    }
}

impl Default for Timer {
    fn default() -> Self {
        Self::set(Duration::ZERO)
    }
}

[theemathas]

Minimal reproducer:

#![feature(min_generic_const_args, generic_const_args)]

fn main() {
    std::time::Duration::ZERO;
}

[khyperia]

lets see if I can do a little writeup on what this issue is... there's probably a better place for this, but, yeah:

consider the two consts:

const REGULAR: u32 = 2;
const TYPESYSTEM: u32 = direct_const_arg!(2);

there are two ways of normalizing a reference to such a const (a ty::AliasConst in rustc):

• with CTFE machinery, producing a MIR value
  • CTFE machinery knows how to evaluate regular consts. It ICEs on direct consts.
• with typesystem normalization, producing a valtree
  • typesystem normalization knows how to evaluate both regular consts as well as direct consts.

these two kinds of values are very different, see boxy's post about "Regular Values" vs. "Type-System Values" https://hackmd.io/1ZJgp6nSQj-8AgclcB2RAg (note I am kind of conflating technical implementation details with theoretical implementation details, while valtrees are currently the technical implementation of a type-system value, this is not necessarily the case)

So, typesystem normalization produces a valtree. Valtrees are significantly less expressive than MIR values: they can't represent pattern types, unions, function pointers, padding bytes, probably more stuff.

Now, consider the following:

#[feature(generic_const_args)]
trait Trait {
    const ASSOC: u32;
}
impl Trait for u8 {
    const ASSOC: u32 = 5;
}
impl Trait for u16 {
    const ASSOC: u32 = direct_const_arg!(10);
}
fn blah<T: Trait>() {
    let x = T::ASSOC;
}

When lowering the reference to T::ASSOC in blah, we need to make a choice: do we lower this as a Const::Unnormalized, which currently(*) uses CTFE machinery to produce the resulting value? Or, do we lower this as Const::Ty, which uses typesystem normalization to produce the resulting value? We don't know which impl we're using yet so we don't know which kind of const it is!

(this is only an issue under generic_const_args, this problem is avoided under min_generic_const_args because you can't impl a non-#[rustc_always_gce] trait with a direct_const_arg! impl)

Go back to our chart: CTFE machinery can evaluate regular consts, but ICEs on direct consts. Typesystem norm can handle both, but doesn't support many types. So, under generic_const_args, we have a hack to always use typesystem norm:

rust/compiler/rustc_mir_build/src/builder/expr/as_constant.rs

Lines 77 to 85 in 971903d

	// Under generic_const_args, `def_id` might be a regular const declared in a trait, but
	// is `impl`d as a directly represented const. We do not know whether it is here, so we
	// must use type system normalization for all consts under generic_const_args.
	// FIXME(generic_const_args): there's a lot to consider here! `Const::Ty` uses valtrees
	// and `Const::Unevaluated` does not, we should revisit this before stabilization.
	let def_kind = tcx.def_kind(def_id);
	if tcx.features().generic_const_args()
	|| matches!(def_kind, DefKind::Const | DefKind::AssocConst)
	&& tcx.is_direct_const(def_id)

This causes ICEs such as this issue, for when typesystem norm can't handle something that really ought to be evaluated with CTFE machinery. Ideally, we would teach Const::Unnormalized how to handle direct-rhs consts instead, and always lower T::ASSOC to that. This is the lil asterisk(*) above, but is a big change, and needs lots of discussion and research, but we're working on it~

[crumblingstatue]

As of latest nightly, this bug doesn't happen at least for my projects, and my repro code above.

[matthiaskrgr]

did you take into account that a bunch of features were renamed in #163306 and did you check all the code snippets in the tickets?

[crumblingstatue]

Yes, I am using the renamed features.
No, I haven't checked all snippets, only my personal projects, and the snippet I made above. I just wanted to notify people that the situation has changed.

[khyperia]

It probably doesn't happen for you anymore due to #162937 - from that PR:

This excludes all anon consts, and regular (not direct) free and inherent consts from being lowered as Const::Ty under full GCA. It does not fix the underlying issue that lowering a potentially regular projection const to Const::Ty is incorrect.

So this bug will now only repro for projection consts. I'm guessing you were running into this bug with an anon, free, or inherent const (e.g. std::time::Duration::ZERO is an inherent const).

But yeah, so, the situation hasn't fundamentally changed. Would be nice to keep this issue open and whatnot to still track the issue~