ICE: could not fully normalize `&<MyType as std::ops::Index<MyType>>::Output

[ABouttefeux]

Code

repo github
Sorry I did not found a minimal code yet, I will try a bit more to find one

Meta

rustc --version --verbose:

rustc 1.56.0-nightly (ac50a5335 2021-08-27)
binary: rustc
commit-hash: ac50a53359328a5d7f2f558833e63d59d372e4f7
commit-date: 2021-08-27
host: x86_64-pc-windows-msvc
release: 1.56.0-nightly
LLVM version: 13.0.0

Error output

error: internal compiler error: compiler\rustc_traits\src\normalize_erasing_regions.rs:54:32: could not fully normalize `&<sudoku::grid::Sudoku<SQUARE_SIZE> as std::ops::Index<sudoku::grid::CellPosition<SQUARE_SIZE>>>::Output`

Backtrace

thread 'rustc' panicked at 'Box<dyn Any>', compiler\rustc_errors\src\lib.rs:1147:9
stack backtrace:
   0:     0x7ff8f7f97ebe - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h6b00b2712108694c
   1:     0x7ff8f7fc270a - core::fmt::write::h7e004fee938dc3bd
   2:     0x7ff8f7f8b388 - <std::io::IoSlice as core::fmt::Debug>::fmt::h54e140a5fa3c615c
   3:     0x7ff8f7f9b956 - std::panicking::take_hook::h58e16e4f2d86f1bc
   4:     0x7ff8f7f9b468 - std::panicking::take_hook::h58e16e4f2d86f1bc
   5:     0x7ff8f1288e35 - <tracing_subscriber::fmt::format::json::WriteAdaptor as std::io::Write>::flush::h9f2e1b987cafdd4f
   6:     0x7ff8f7f9c250 - std::panicking::rust_panic_with_hook::h9229e1b31882af1c
   7:     0x7ff8f586ae60 - <rustc_errors::styled_buffer::StyledChar as core::fmt::Debug>::fmt::h94c8a259f157b41b
   8:     0x7ff8f586ade9 - <rustc_errors::styled_buffer::StyledChar as core::fmt::Debug>::fmt::h94c8a259f157b41b
   9:     0x7ff8f5b349d1 - rustc_query_system::query::job::report_cycle::hc18b9b1edf140a65
  10:     0x7ff8f5898c10 - <rustc_errors::json::Diagnostic::from_errors_diagnostic::BufWriter as std::io::Write>::flush::hd123965c617bf938
  11:     0x7ff8f58a0cc5 - rustc_errors::HandlerInner::emit_diagnostic::h793e03cee5f71ce6
  12:     0x7ff8f589e772 - rustc_errors::Handler::bug::h4ae88d4a87e0a336
  13:     0x7ff8f5753c87 - rustc_middle::traits::select::EvaluationResult::is_stack_dependent::h0844dc638e85f719
  14:     0x7ff8f57536f0 - rustc_middle::traits::select::EvaluationResult::is_stack_dependent::h0844dc638e85f719
  15:     0x7ff8f5753698 - rustc_middle::traits::select::EvaluationResult::is_stack_dependent::h0844dc638e85f719
  16:     0x7ff8f5753bb9 - rustc_middle::traits::select::EvaluationResult::is_stack_dependent::h0844dc638e85f719
  17:     0x7ff8f5b31787 - rustc_middle::util::bug::bug_fmt::hf202c2d3ce8ef8a0
  18:     0x7ff8f44baa74 - <&chalk_ir::GenericArg<rustc_middle::traits::chalk::RustInterner> as rustc_traits::chalk::lowering::LowerInto<rustc_middle::ty::subst::GenericArg>>::lower_into::hc2ebc8226c9618cd
  19:     0x7ff8f4599c83 - <rustc_traits::chalk::db::RustIrDatabase as chalk_ir::UnificationDatabase<rustc_middle::traits::chalk::RustInterner>>::adt_variance::hf616762a148fb70e
  20:     0x7ff8f49e61df - <rustc_span::def_id::DefIndex as rustc_query_impl::profiling_support::SpecIntoSelfProfilingString>::spec_to_self_profile_string::h84310f1d53aae64b
  21:     0x7ff8f4997823 - <rustc_span::def_id::DefIndex as rustc_query_impl::profiling_support::SpecIntoSelfProfilingString>::spec_to_self_profile_string::h84310f1d53aae64b
  22:     0x7ff8f4ab194f - rustc_query_impl::on_disk_cache::__ty_decoder_impl::<impl rustc_serialize::serialize::Decoder for rustc_query_impl::on_disk_cache::CacheDecoder>::error::h23d06995eb6cfeec
  23:     0x7ff8f4678366 - <fixedbitset::FixedBitSet as core::fmt::Debug>::fmt::h467ffd2e0734ab57
  24:     0x7ff8f4a3e67b - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_mark_green::h19da6eec48ba9884
  25:     0x7ff8f5651091 - rustc_middle::ty::flags::FlagComputation::for_unevaluated_const::hc73a3b6d731bff72
  26:     0x7ff8f5612f1e - rustc_middle::ty::util::needs_drop_components::hebe752db6906a070
  27:     0x7ff8f55be684 - rustc_middle::ty::inhabitedness::<impl rustc_middle::ty::context::TyCtxt>::is_ty_uninhabited_from::h3b5342db4c7fe350
  28:     0x7ff8f56b928c - rustc_middle::ty::layout::<impl rustc_middle::ty::instance::Instance>::fn_sig_for_fn_abi::h81cb02eac6bf2c1f
  29:     0x7ff8f157ec8e - <rustc_codegen_llvm::builder::Builder as rustc_codegen_ssa::traits::builder::BuilderMethods>::unchecked_umul::h94bfdb69f0bb5214
  30:     0x7ff8f154b2cb - rustc_codegen_llvm::mono_item::<impl rustc_codegen_ssa::traits::declare::PreDefineMethods for rustc_codegen_llvm::context::CodegenCx>::predefine_fn::h18036dc992cd6855
  31:     0x7ff8f15632df - <rustc_codegen_llvm::base::ValueIter as core::iter::traits::iterator::Iterator>::next::hfabb5c09af5de8b3
  32:     0x7ff8f14d4f8e - <rustc_codegen_llvm::llvm_::archive_ro::Child as core::ops::drop::Drop>::drop::hdd17f77e5db02b01
  33:     0x7ff8f152dc66 - <rustc_codegen_llvm::back::lto::ThinLTOKeysMap as core::fmt::Debug>::fmt::h0c51d478f12fbf1b
  34:     0x7ff8f1562bd9 - <rustc_codegen_llvm::base::ValueIter as core::iter::traits::iterator::Iterator>::next::hfabb5c09af5de8b3
  35:     0x7ff8f150368e - <rustc_codegen_llvm::builder::Builder as core::ops::drop::Drop>::drop::h0ff57be597133e74
  36:     0x7ff8f154d9bb - <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate::hc453fef2a1a5be0a
  37:     0x7ff8f13d1d56 - rustc_interface::queries::Queries::ongoing_codegen::h6eaba3ff4becc117
  38:     0x7ff8f12ddac8 - <rustc_span::symbol::SymbolStr as core::fmt::Display>::fmt::hc7ceaa6abc25db7f
  39:     0x7ff8f12a8275 - rustc_driver::pretty::print_after_hir_lowering::h305824134be04e10
  40:     0x7ff8f12dfa07 - <rustc_span::symbol::SymbolStr as core::fmt::Display>::fmt::hc7ceaa6abc25db7f
  41:     0x7ff8f12b2f50 - <rustc_span::symbol::SymbolStr as core::fmt::Display>::fmt::hc7ceaa6abc25db7f
  42:     0x7ff8f12adda8 - <tracing_subscriber::util::TryInitError as core::fmt::Display>::fmt::h17e85dfc411e4143
  43:     0x7ff8f129da0d - <rustc_driver::Compilation as core::fmt::Debug>::fmt::h580e7f1b5da2df06
  44:     0x7ff8f7faa47c - std::sys::windows::thread::Thread::new::h4f56ff2d056f7249
  45:     0x7ff992cd7034 - BaseThreadInitThunk
  46:     0x7ff9948a2651 - RtlUserThreadStart

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 (ac50a5335 2021-08-27) running on x86_64-pc-windows-msvc

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 [normalize_generic_arg_after_erasing_regions] normalizing `&<sudoku::grid::Sudoku<SQUARE_SIZE> as std::ops::Index<sudoku::grid::CellPosition<SQUARE_SIZE>>>::Output`
end of query stack
error: could not compile `sudoku`

[hellow554]

Needs an external crate for it to work! In this case I use a lib.rs and main.rs in the same project. cargo build is also needed.

main.rs:

fn main() {
    ext::Sudoku::<3>::random();
}

lib.rs:

#![feature(const_generics)]
#![feature(const_evaluatable_checked)]

use std::ops::Index;

pub struct CellPossibilities;

pub enum CellState<const SQUARE_SIZE: usize> {
    Empty(Option<CellPossibilities>),
}

pub struct Sudoku<const SQUARE_SIZE: usize>;

impl<const SQUARE_SIZE: usize> Sudoku<SQUARE_SIZE>where
    [CellState<SQUARE_SIZE>; SQUARE_SIZE * SQUARE_SIZE]: Sized,
{
    pub fn random() {
        let CellState::Empty(_) = Self[()];
    }
}

impl<const SQUARE_SIZE: usize> Index<()> for Sudoku<SQUARE_SIZE>
where
    [CellState<SQUARE_SIZE>; SQUARE_SIZE * SQUARE_SIZE]: Sized,
{
    type Output = CellState<SQUARE_SIZE>;

    fn index(&self, _: ()) -> &Self::Output {
        todo!()
    }
}

Regression in nightly-2020-09-25 8b40853...e599b53

[jackh726]

Works fine in latest nightly.