"internal compiler error: cannot relate constants" from const generic expression using generic associated types

[chc4]

I was writing some code that uses traits with generic associated types and hit an ICE when adding const generic bounds to a function.

Code

Playground link

I couldn't easily minimize it much more than this, unfortunately. The bound in question is Equal<{ core::mem::size_of::<T>() }, { core::mem::size_of::<U>() }>: True, and goes away if you remove the TO and FROM functions and definitions in the Tokenize trait. The ICE goes away if you change the left-hand to core::mem::size_of::<T>() as usize instead.

Meta

rustc --version --verbose:

rustc 1.69.0-nightly (2773383a3 2023-02-10)
binary: rustc
commit-hash: 2773383a314a4b8f481ce2bed12c32de794ffbe9
commit-date: 2023-02-10
host: x86_64-unknown-linux-gnu
release: 1.69.0-nightly
LLVM version: 15.0.7

Error output

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: cannot relate constants (Const { ty: fn() -> usize {std::mem::size_of::<_>}, kind: Value(Branch([])) }, Const { ty: fn() -> usize {std::mem::size_of::<_>}, kind: Value(Branch([])) }) of different types: fn() -> usize {std::mem::size_of::<_>} != fn() -> usize {std::mem::size_of::<_>}
  |
  = note: delayed at    0: <rustc_errors::HandlerInner>::emit_diagnostic

Backtrace

0: <rustc_errors::HandlerInner>::emit_diagnostic
             1: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, &alloc::string::String>
             2: rustc_middle::ty::relate::super_relate_consts::<rustc_infer::infer::equate::Equate>
             3: <rustc_infer::infer::InferCtxt>::super_combine_consts::<rustc_infer::infer::equate::Equate>
             4: rustc_middle::ty::relate::super_relate_consts::<rustc_infer::infer::equate::Equate>
             5: <rustc_infer::infer::InferCtxt>::super_combine_consts::<rustc_infer::infer::equate::Equate>
             6: <rustc_infer::infer::InferCtxt>::commit_if_ok::<rustc_infer::infer::InferOk<()>, rustc_middle::ty::error::TypeError, <rustc_infer::infer::at::Trace>::eq<rustc_middle::ty::consts::Const>::{closure#0}>
             7: <rustc_infer::infer::at::At>::eq::<rustc_middle::ty::consts::Const>
             8: <rustc_trait_selection::traits::fulfill::FulfillProcessor as rustc_data_structures::obligation_forest::ObligationProcessor>::process_obligation
             9: <rustc_data_structures::obligation_forest::ObligationForest<rustc_trait_selection::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection::traits::fulfill::FulfillProcessor>
            10: <rustc_trait_selection::traits::fulfill::FulfillmentContext as rustc_infer::traits::engine::TraitEngine>::select_where_possible
            11: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
            12: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_return_expr
            13: rustc_hir_typeck::check::check_fn
            14: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_closure
            15: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
            16: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_argument_types
            17: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
            18: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_argument_types
            19: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_call
            20: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
            21: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_block_with_expected
            22: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
            23: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_return_expr
            24: rustc_hir_typeck::check::check_fn
            25: rustc_hir_typeck::typeck
            26: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::typeck, rustc_query_impl::plumbing::QueryCtxt>
            27: rustc_data_structures::sync::par_for_each_in::<&[rustc_span::def_id::LocalDefId], <rustc_middle::hir::map::Map>::par_body_owners<rustc_hir_typeck::typeck_item_bodies::{closure#0}>::{closure#0}>
            28: rustc_hir_typeck::typeck_item_bodies
            29: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::typeck_item_bodies, rustc_query_impl::plumbing::QueryCtxt>
            30: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck_item_bodies
            31: <rustc_session::session::Session>::time::<(), rustc_hir_analysis::check_crate::{closure#7}>
            32: rustc_hir_analysis::check_crate
            33: rustc_interface::passes::analysis
            34: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt>
            35: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
            36: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_driver_impl::run_compiler::{closure#1}::{closure#2}::{closure#3}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            37: <rustc_interface::interface::Compiler>::enter::<rustc_driver_impl::run_compiler::{closure#1}::{closure#2}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_errors::ErrorGuaranteed>>
            38: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
            39: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            40: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            41: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
            42: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/2773383a314a4b8f481ce2bed12c32de794ffbe9/library/alloc/src/boxed.rs:1988:9
            43: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/2773383a314a4b8f481ce2bed12c32de794ffbe9/library/alloc/src/boxed.rs:1988:9
            44: std::sys::unix::thread::Thread::new::thread_start
                       at /rustc/2773383a314a4b8f481ce2bed12c32de794ffbe9/library/std/src/sys/unix/thread.rs:108:17
            45: start_thread
                       at ./nptl/./nptl/pthread_create.c:442:8
            46: clone3
                       at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

[clubby789]

@rustbot label +regression-from-stable-to-nightly

[clubby789]

searched nightlies: from nightly-2023-01-20 to nightly-2023-02-11
regressed nightly: nightly-2023-02-06
searched commit range: 50d3ba5...75a0be9
regressed commit: 2a6ff72

bisected with cargo-bisect-rustc v0.6.5

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc 2023-01-20 --regress=ice 

Regressed in #107434, same issue as #107898 I think

[BoxyUwU]

Almost certainly a dupe of #107898, dont see any value in having both issues open. Thanks for the issue anyway :)