Computing and checking generics of type which uses const generics

[ViliamVadocz]

Code

I tried simplifying my code, but the code is quite complex and I wasn't able to recreate the ICE. Here is the repo which you can try building to see it for yourself: https://github.com/ViliamVadocz/Onitama-Alpha-Zero

The main source of the issue is my Tensor structs which look similar to the below code. I have had issues with this in the past. The ICE started happening after I added convolution with fft. I use a const fn to simplify writing the types. Maybe it's related? Sorry for the code mess; I didn't plan to show this code to other people.

#![feature(const_generics, const_evaluatable_checked)]
#![allow(incomplete_features)]

trait Tensor<T, const X: usize>: Sized {
    fn new(data: [T; X]) -> Self;
    fn get_data(self) -> [T; X];
    fn reshape<G: Tensor<T, X>>(self) -> G {
        G::new(self.get_data())
    }
}

struct Tensor1<T, const L: usize>([T; L]);
impl<T, const L: usize> Tensor<T, L> for Tensor1<T, L> {
    fn new(data: [T; L]) -> Self {
        Tensor1(data)
    }
    fn get_data(self) -> [T; L] {
        self.0
    }
}

struct Tensor2<T, const R: usize, const C: usize>([T; R * C])
where
    [(); R * C]: ;
impl<T, const R: usize, const C: usize> Tensor<T, { R * C }> for Tensor2<T, R, C>
where
    [(); R * C]: ,
{
    fn new(data: [T; R * C]) -> Self {
        Tensor2(data)
    }
    fn get_data(self) -> [T; R * C] {
        self.0
    }
}

struct Tensor3<T, const R: usize, const C: usize, const D: usize>([T; R * C * D])
where
    [(); R * C * D]: ;
impl<T, const R: usize, const C: usize, const D: usize> Tensor<T, { R * C * D }> for Tensor3<T, R, C, D>
where
    [(); R * C * D]: ,
{
    fn new(data: [T; R * C * D]) -> Self {
        Tensor3(data)
    }
    fn get_data(self) -> [T; R * C * D] {
        self.0
    }
}

Meta

rustc --version --verbose:

rustc 1.56.0-nightly (1f0a591b3 2021-07-30)
binary: rustc
commit-hash: 1f0a591b3a5963a0ab11a35dc525ad9d46f612e4
commit-date: 2021-07-30
host: x86_64-pc-windows-gnu
release: 1.56.0-nightly
LLVM version: 12.0.1

Error output

> cargo build
   Compiling tensor v0.1.0 (D:\Code\Onitama-Alpha-Zero\tensor)
   Compiling onitama-alpha-zero v0.1.0 (D:\Code\Onitama-Alpha-Zero)
thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', compiler\rustc_metadata\src\rmeta\decoder.rs:914:54

Backtrace

stack backtrace:
   0: rust_begin_unwind
             at /rustc/1f0a591b3a5963a0ab11a35dc525ad9d46f612e4\/library\std\src/panicking.rs:516:5
   1: core::panicking::panic_fmt
             at /rustc/1f0a591b3a5963a0ab11a35dc525ad9d46f612e4\/library\core\src/panicking.rs:93:14
   2: core::panicking::panic
             at /rustc/1f0a591b3a5963a0ab11a35dc525ad9d46f612e4\/library\core\src/panicking.rs:50:5
   3: rustc_metadata::rmeta::decoder::<impl rustc_metadata::creader::CrateMetadataRef>::get_generics
   4: rustc_metadata::rmeta::decoder::cstore_impl::provide_extern::generics_of
   5: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
   6: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
   7: rustc_data_structures::stack::ensure_sufficient_stack
   8: rustc_query_system::query::plumbing::force_query_with_job
   9: rustc_query_system::query::plumbing::get_query_impl
  10: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::generics_of
  11: <rustc_middle::ty::print::pretty::FmtPrinter<F> as rustc_middle::ty::print::Printer>::print_def_path
  12: <rustc_middle::ty::print::pretty::FmtPrinter<F> as rustc_middle::ty::print::Printer>::print_def_path
  13: <rustc_middle::ty::instance::Instance as core::fmt::Display>::fmt
  14: std::thread::local::LocalKey<T>::with
  15: rustc_mir::const_eval::eval_queries::eval_to_allocation_raw_provider
  16: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  17: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  18: rustc_data_structures::stack::ensure_sufficient_stack
  19: rustc_query_system::query::plumbing::get_query_impl
  20: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::eval_to_allocation_raw
  21: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  22: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  23: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  24: rustc_data_structures::stack::ensure_sufficient_stack
  25: rustc_query_system::query::plumbing::get_query_impl
  26: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::eval_to_const_value_raw
  27: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  28: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  29: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  30: rustc_data_structures::stack::ensure_sufficient_stack
  31: rustc_query_system::query::plumbing::get_query_impl
  32: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::eval_to_const_value_raw
  33: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_global_id
  34: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_resolve
  35: rustc_middle::ty::consts::kind::ConstKind::try_eval
  36: rustc_middle::ty::inhabitedness::type_uninhabited_from
  37: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  38: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  39: rustc_data_structures::stack::ensure_sufficient_stack
  40: rustc_query_system::query::plumbing::get_query_impl
  41: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::type_uninhabited_from
  42: rustc_middle::ty::inhabitedness::<impl rustc_middle::ty::TyS>::uninhabited_from
  43: rustc_middle::ty::inhabitedness::<impl rustc_middle::ty::FieldDef>::uninhabited_from
  44: rustc_middle::ty::inhabitedness::def_id_forest::DefIdForest::union
  45: rustc_middle::ty::inhabitedness::def_id_forest::DefIdForest::intersection
  46: rustc_middle::ty::inhabitedness::type_uninhabited_from
  47: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  48: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  49: rustc_data_structures::stack::ensure_sufficient_stack
  50: rustc_query_system::query::plumbing::get_query_impl
  51: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::type_uninhabited_from
  52: rustc_middle::ty::inhabitedness::<impl rustc_middle::ty::TyS>::uninhabited_from
  53: rustc_middle::ty::inhabitedness::<impl rustc_middle::ty::context::TyCtxt>::is_ty_uninhabited_from
  54: rustc_passes::liveness::Liveness::propagate_through_expr
  55: rustc_passes::liveness::Liveness::propagate_through_expr
  56: <rustc_passes::liveness::IrMaps as rustc_hir::intravisit::Visitor>::visit_body
  57: rustc_hir::intravisit::walk_fn
  58: rustc_hir::intravisit::Visitor::visit_fn
  59: rustc_hir::intravisit::walk_expr
  60: <rustc_passes::liveness::IrMaps as rustc_hir::intravisit::Visitor>::visit_expr
  61: rustc_hir::intravisit::walk_expr
  62: rustc_hir::intravisit::walk_block
  63: <rustc_passes::liveness::IrMaps as rustc_hir::intravisit::Visitor>::visit_body
  64: rustc_hir::intravisit::walk_item
  65: rustc_middle::hir::map::Map::visit_item_likes_in_module
  66: rustc_passes::liveness::check_mod_liveness
  67: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  68: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  69: rustc_data_structures::stack::ensure_sufficient_stack
  70: rustc_query_system::query::plumbing::force_query_with_job
  71: rustc_query_system::query::plumbing::get_query_impl
  72: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::check_mod_liveness
  73: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  74: rustc_session::utils::<impl rustc_session::session::Session>::time
  75: rustc_interface::passes::analysis
  76: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  77: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  78: rustc_data_structures::stack::ensure_sufficient_stack
  79: rustc_query_system::query::plumbing::force_query_with_job
  80: rustc_query_system::query::plumbing::get_query_impl
  81: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
  82: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  83: rustc_span::with_source_map
  84: rustc_interface::interface::create_compiler_and_run
  85: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

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 1.56.0-nightly (1f0a591b3 2021-07-30) running on x86_64-pc-windows-gnu

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

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

query stack during panic:
#0 [generics_of] computing generics of `tensor::Tensor3::0`
#1 [eval_to_allocation_raw] const-evaluating + checking `tensor::Tensor3::0::{constant#0}`
#2 [eval_to_const_value_raw] simplifying constant for the type system `tensor::Tensor3::0::{constant#0}`
#3 [eval_to_const_value_raw] simplifying constant for the type system `tensor::Tensor3::0::{constant#0}`
#4 [type_uninhabited_from] computing the inhabitedness of `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [Binder(ConstEvaluatable(WithOptConstParam { 
did: DefId(0:170 ~ onitama_alpha_zero[d450]::network::bp_convolution::{constant#2}), const_param_did: None }, [Const { ty: usize, val: Param(A/#0) }, Const { ty: usize, val: Param(B/#1) }]), []), Binder(ConstEvaluatable(WithOptConstParam { did: DefId(0:169 ~ onitama_alpha_zero[d450]::network::bp_convolution::{constant#1}), const_param_did: None }, [Const { ty: usize, val: Param(A/#0) }, Const { ty: usize, val: Param(B/#1) }]), []), Binder(ConstEvaluatable(WithOptConstParam { did: DefId(0:168 ~ onitama_alpha_zero[d450]::network::bp_convolution::{constant#0}), const_param_did: None }, [Const { ty: usize, val: Param(A/#0) }, Const { ty: usize, val: Param(B/#1) }]), []), Binder(OutlivesPredicate([(); _], ReEmpty(U0)), []), Binder(OutlivesPredicate([(); _], ReEmpty(U0)), []), Binder(OutlivesPredicate([(); _], ReEmpty(U0)), [])], reveal: UserFacing }, value: [f64; _] }`
#5 [type_uninhabited_from] computing the inhabitedness of `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [Binder(ConstEvaluatable(WithOptConstParam { 
did: DefId(0:170 ~ onitama_alpha_zero[d450]::network::bp_convolution::{constant#2}), const_param_did: None }, [Const { ty: usize, val: Param(A/#0) }, Const { ty: usize, val: Param(B/#1) }]), []), Binder(ConstEvaluatable(WithOptConstParam { did: DefId(0:169 ~ onitama_alpha_zero[d450]::network::bp_convolution::{constant#1}), const_param_did: None }, [Const { ty: usize, val: Param(A/#0) }, Const { ty: usize, val: Param(B/#1) }]), []), Binder(ConstEvaluatable(WithOptConstParam { did: DefId(0:168 ~ onitama_alpha_zero[d450]::network::bp_convolution::{constant#0}), const_param_did: None }, [Const { ty: usize, val: Param(A/#0) }, Const { ty: usize, val: Param(B/#1) }]), []), Binder(OutlivesPredicate([(); _], ReEmpty(U0)), []), Binder(OutlivesPredicate([(); _], ReEmpty(U0)), []), Binder(OutlivesPredicate([(); _], ReEmpty(U0)), [])], reveal: UserFacing }, value: tensor::Tensor3<f64, 3_usize, 3_usize, A> }`
#6 [check_mod_liveness] checking liveness of variables in module `network`
#7 [analysis] running analysis passes on this crate
end of query stack

[ViliamVadocz]

Please add A-const-generics, F-const_evaluatable_checked, and F-const_generics labels

[ViliamVadocz]

Maybe related to #87603, but I had this ICE already all the way back in 04/06/2021.
Back then the error was

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', compiler\rustc_metadata\src\rmeta\decoder.rs:906:54

[BoxyUwU]

Smaller repro of ICE:

// lib.rs
#![feature(const_generics, const_evaluatable_checked)]
#![allow(incomplete_features)]

pub struct Foo<const N: usize>([(); N + 1])
where
    [(); N + 1]: ;

// main.rs
#![feature(const_generics, const_evaluatable_checked)]
#![allow(incomplete_features)]

use ice::Foo;

fn new<U>(a: U) -> U {
    a
}

fn foo<const N: usize>(bar: &mut Foo<N>)
where
    [(); N + 1]: ,
{
    *bar = new(loop {});
}

fn main() {}

[0ble]

Maybe related to #87603

confirming #87603 potentially predates 1.56 nightly