[ICE] Const generics + Const normalization + Specialization

Found while toying around #20400.

Code

#![feature(const_generics)]
#![feature(specialization)]
#![allow(incomplete_features)]

//--------------------------------------------------

trait Depth {
    const C: usize;
}

trait Type {
    type AT: Depth;
}

//--------------------------------------------------

enum Predicate<const B: bool> {}

trait Satisfied {}

impl Satisfied for Predicate<true> {}

//--------------------------------------------------

trait Spec1 {}

impl<T: Type> Spec1 for T where Predicate<{T::AT::C > 0}>: Satisfied {}

trait Spec2: Spec1 {}

impl<T: Type + Spec1> Spec2 for T where Predicate<{T::AT::C > 1}>: Satisfied {}

//--------------------------------------------------

trait Foo {
    fn Bar();
}

impl<T: Spec1> Foo for T {
    default fn Bar() {}
}

impl<T: Spec2> Foo for T {
    fn Bar() {}
}

Error output

error: internal compiler error: src/librustc_traits/normalize_erasing_regions.rs:37: could not fully normalize `Const { ty: usize, val: Unevaluated(DefId(0:4 ~ playground[3575]::Depth[0]::C[0]), [<T as Type>::AT], None) }`

Backtrace

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:907:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1076
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1537
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:490
  12: std::panicking::begin_panic
  13: rustc_errors::HandlerInner::bug
  14: rustc_errors::Handler::bug
  15: rustc_middle::util::bug::opt_span_bug_fmt::{{closure}}
  16: rustc_middle::ty::context::tls::with_opt::{{closure}}
  17: rustc_middle::ty::context::tls::with_opt
  18: rustc_middle::util::bug::opt_span_bug_fmt
  19: rustc_middle::util::bug::bug_fmt
  20: rustc_middle::ty::context::GlobalCtxt::enter_local
  21: rustc_traits::normalize_erasing_regions::normalize_generic_arg_after_erasing_regions
  22: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::normalize_generic_arg_after_erasing_regions>::compute
  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_middle::ty::normalize_erasing_regions::NormalizeAfterErasingRegionsFolder as rustc_middle::ty::fold::TypeFolder>::fold_const
  27: rustc_middle::ty::normalize_erasing_regions::<impl rustc_middle::ty::context::TyCtxt>::subst_and_normalize_erasing_regions
  28: rustc_mir::interpret::operand::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_operand
  29: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_rvalue_into_place
  30: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::run
  31: rustc_mir::const_eval::eval_queries::const_eval_raw_provider
  32: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::const_eval_raw>::compute
  33: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  34: rustc_query_system::query::plumbing::get_query_impl::{{closure}}
  35: rustc_query_system::query::plumbing::get_query_impl
  36: rustc_mir::const_eval::eval_queries::const_eval_validated_provider
  37: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::const_eval_validated>::compute
  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_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_global_id
  42: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_resolve
  43: rustc_infer::infer::InferCtxt::const_eval_resolve
  44: <rustc_trait_selection::traits::fulfill::FulfillProcessor as rustc_data_structures::obligation_forest::ObligationProcessor>::process_obligation::{{closure}}
  45: rustc_data_structures::obligation_forest::ObligationForest<O>::process_obligations
  46: <rustc_trait_selection::traits::fulfill::FulfillmentContext as rustc_infer::traits::engine::TraitEngine>::select_where_possible
  47: <rustc_trait_selection::traits::fulfill::FulfillmentContext as rustc_infer::traits::engine::TraitEngine>::select_all_or_error
  48: rustc_infer::infer::InferCtxt::save_and_restore_in_snapshot_flag
  49: rustc_trait_selection::traits::specialize::fulfill_implication
  50: rustc_middle::ty::context::GlobalCtxt::enter_local
  51: rustc_trait_selection::traits::specialize::specializes
  52: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::specializes>::compute
  53: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  54: rustc_data_structures::stack::ensure_sufficient_stack
  55: rustc_query_system::query::plumbing::get_query_impl
  56: rustc_middle::ty::context::GlobalCtxt::enter_local
  57: rustc_trait_selection::traits::coherence::overlapping_impls
  58: <rustc_middle::traits::specialization_graph::Children as rustc_trait_selection::traits::specialize::specialization_graph::ChildrenExt>::insert
  59: <rustc_middle::traits::specialization_graph::Graph as rustc_trait_selection::traits::specialize::specialization_graph::GraphExt>::insert
  60: rustc_trait_selection::traits::specialize::specialization_graph_provider
  61: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::specialization_graph_of>::compute
  62: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  63: rustc_data_structures::stack::ensure_sufficient_stack
  64: rustc_query_system::query::plumbing::get_query_impl
  65: rustc_query_system::query::plumbing::ensure_query_impl
  66: rustc_typeck::coherence::coherent_trait
  67: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::coherent_trait>::compute
  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::get_query_impl
  71: rustc_query_system::query::plumbing::ensure_query_impl
  72: rustc_typeck::coherence::check_coherence
  73: rustc_typeck::check_crate
  74: rustc_interface::passes::analysis
  75: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  76: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  77: rustc_query_system::query::plumbing::get_query_impl
  78: rustc_middle::ty::context::tls::enter_global
  79: rustc_interface::interface::run_compiler_in_existing_thread_pool
  80: rustc_ast::attr::with_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.45.0-nightly (74e804683 2020-05-30) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 --crate-type lib

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

query stack during panic:
#0 [normalize_generic_arg_after_erasing_regions] normalizing `<<T as Type>::AT as Depth>::C`
#1 [const_eval_raw] const-evaluating `<T as Spec2>::{{constant}}#0`
#2 [const_eval_validated] const-evaluating + checking `<T as Spec2>::{{constant}}#0`
#3 [specializes] computing whether impls specialize one another
#4 [specialization_graph_of] building specialization graph of trait `Foo`
#5 [coherent_trait] coherence checking all impls of trait `Foo`
#6 [analysis] running analysis passes on this crate
end of query stack

@rustbot

This ICEs since 1.45
@rustbot modify labels: +regression-from-stable-to-stable

Rollup merge of rust-lang#91551 - b-naber:const-eval-normalization-ic…

Well, this still crashes if I add a main function or check with --crate-type lib

warning: trait method `Bar` should have a snake case name
  --> ./72845.rs:36:8
   |
36 |     fn Bar();
   |        ^^^ help: convert the identifier to snake case: `bar`
   |
   = note: `#[warn(non_snake_case)]` on by default

warning: 1 warning emitted

error: internal compiler error: failed to normalize <<T as Type>::AT as Depth>::C
  |
  = note: delayed at compiler/rustc_const_eval/src/interpret/eval_context.rs:527:31

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:1189:13
stack backtrace:
   0:     0x7f17cb4cc35c - std::backtrace_rs::backtrace::libunwind::trace::hf7449935ead7573e
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f17cb4cc35c - std::backtrace_rs::backtrace::trace_unsynchronized::h221aa2d88d72372a
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f17cb4cc35c - std::sys_common::backtrace::_print_fmt::h1c77e8983e1df895
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f17cb4cc35c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hd4ec41a9a6b0d22c
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7f17cb52937c - core::fmt::write::h72801a82c94e6ff1
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/core/src/fmt/mod.rs:1149:17
   5:     0x7f17cb4bca65 - std::io::Write::write_fmt::haf74340a8cbeaa88
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/io/mod.rs:1660:15
   6:     0x7f17cb4cf520 - std::sys_common::backtrace::_print::h2d15cd157796a64a
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7f17cb4cf520 - std::sys_common::backtrace::print::h52d286d22e2398eb
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7f17cb4cf520 - std::panicking::default_hook::{{closure}}::h6da08fba6306daf2
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/panicking.rs:211:50
   9:     0x7f17cb4cf0cb - std::panicking::default_hook::h266f67a22e76b11a
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/panicking.rs:228:9
  10:     0x7f17cbff3291 - rustc_driver[feb513e6adc957d8]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7f17cb4cfd39 - std::panicking::rust_panic_with_hook::he55698a957f4fb6d
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/panicking.rs:610:17
  12:     0x7f17cb4cf7f0 - std::panicking::begin_panic_handler::{{closure}}::h01f453c3ac181895
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/panicking.rs:502:13
  13:     0x7f17cb4cc804 - std::sys_common::backtrace::__rust_end_short_backtrace::h675d77c6e5a3926d
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/sys_common/backtrace.rs:139:18
  14:     0x7f17cb4cf759 - rust_begin_unwind
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/panicking.rs:498:5
  15:     0x7f17cb493c21 - core::panicking::panic_fmt::h7b8580d81fcbbacd
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/core/src/panicking.rs:107:14
  16:     0x7f17cd12fe9c - core[cc79c391059f8e46]::panicking::panic_display::<&str>
  17:     0x7f17ce7c4e7a - <rustc_errors[248f3f311c690252]::HandlerInner>::flush_delayed
  18:     0x7f17ce7c35fd - <rustc_errors[248f3f311c690252]::HandlerInner as core[cc79c391059f8e46]::ops::drop::Drop>::drop
  19:     0x7f17cdea73b6 - core[cc79c391059f8e46]::ptr::drop_in_place::<rustc_session[2680299e10ec9d86]::parse::ParseSess>
  20:     0x7f17cdea9a9a - <alloc[1954047e53701c4d]::rc::Rc<rustc_session[2680299e10ec9d86]::session::Session> as core[cc79c391059f8e46]::ops::drop::Drop>::drop
  21:     0x7f17cde8496d - core[cc79c391059f8e46]::ptr::drop_in_place::<rustc_interface[4c4b5644b43577f1]::interface::Compiler>
  22:     0x7f17cde84332 - rustc_span[dda57b1885b40b9a]::with_source_map::<core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>, rustc_interface[4c4b5644b43577f1]::interface::create_compiler_and_run<core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>, rustc_driver[feb513e6adc957d8]::run_compiler::{closure#1}>::{closure#1}>
  23:     0x7f17cde887ef - <scoped_tls[3fea4c3dcac147b1]::ScopedKey<rustc_span[dda57b1885b40b9a]::SessionGlobals>>::set::<rustc_interface[4c4b5644b43577f1]::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface[4c4b5644b43577f1]::interface::run_compiler<core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>, rustc_driver[feb513e6adc957d8]::run_compiler::{closure#1}>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>>::{closure#0}::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>>
  24:     0x7f17cde86995 - std[f24903a91e569aa2]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[4c4b5644b43577f1]::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface[4c4b5644b43577f1]::interface::run_compiler<core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>, rustc_driver[feb513e6adc957d8]::run_compiler::{closure#1}>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>>
  25:     0x7f17cdea6ffa - <<std[f24903a91e569aa2]::thread::Builder>::spawn_unchecked<rustc_interface[4c4b5644b43577f1]::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface[4c4b5644b43577f1]::interface::run_compiler<core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>, rustc_driver[feb513e6adc957d8]::run_compiler::{closure#1}>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[248f3f311c690252]::ErrorReported>>::{closure#1} as core[cc79c391059f8e46]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  26:     0x7f17cb4dae23 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4beb69a85f7fb16c
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/alloc/src/boxed.rs:1811:9
  27:     0x7f17cb4dae23 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hef865a799f44aaf2
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/alloc/src/boxed.rs:1811:9
  28:     0x7f17cb4dae23 - std::sys::unix::thread::Thread::new::thread_start::hee0b2d4e2414fa96
                               at /rustc/0b42deaccc2cbe17a68067aa5fdb76104369e1fd/library/std/src/sys/unix/thread.rs:108:17
  29:     0x7f17cb3e8259 - start_thread
  30:     0x7f17cb2fd5e3 - __GI___clone
  31:                0x0 - <unknown>

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 1.59.0-nightly (0b42deacc 2021-12-09) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib

query stack during panic:
end of query stack

Good catch, the test case is slightly different to the one in glacier

--- glacier.rs 2021-12-09 22:59:25.365148200 +0000
+++ test.rs 2021-12-09 23:02:06.135999800 +0000
@@ -26,9 +26,10 @@

 impl<T: Type> Spec1 for T where Predicate<{T::AT::C > 0}>: Satisfied {}

-trait Spec2: Spec1 {}
+trait Spec2 {}

-impl<T: Type + Spec1> Spec2 for T where Predicate<{T::AT::C > 1}>: Satisfied {}
+//impl<T: Type > Spec2 for T where Predicate<{T::AT::C > 1}>: Satisfied {}
+impl<T: Type > Spec2 for T where Predicate<true>: Satisfied {}

 //--------------------------------------------------

Restore 72845 with fn main

const generics triage.

This still causes an ICE with the following code.

#![feature(generic_const_exprs)]
#![feature(specialization)]
#![allow(incomplete_features)]

//--------------------------------------------------

trait Depth {
    const C: usize;
}

trait Type {
    type At: Depth;
}

//--------------------------------------------------

enum Predicate<const B: bool> {}

trait Satisfied {}

impl Satisfied for Predicate<true> {}

//--------------------------------------------------

trait Spec1 {}

impl<T: Type> Spec1 for T where Predicate<{ T::At::C > 0 }>: Satisfied {}

trait Spec2: Spec1 {}

impl<T: Type + Spec1> Spec2 for T where Predicate<{ T::At::C > 1 }>: Satisfied {}

//--------------------------------------------------

trait Foo {
    fn Bar();
}

impl<T: Spec1> Foo for T {
    default fn Bar() {}
}

impl<T: Spec2> Foo for T {
    fn Bar() {}
}

seems interesting, probably caused by rust-lang/project-const-generics#37

No longer ICEs since #108821, I would presume due to #108803

Test was added as const-generics/issues/issue-72845.rs , closing

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[ICE] Const generics + Const normalization + Specialization #72845

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[ICE] Const generics + Const normalization + Specialization #72845

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matthiaskrgr commented on Dec 20, 2020

matthiaskrgr commented on Dec 9, 2021

Alexendoo commented on Dec 9, 2021

lcnr commented on Jun 28, 2022

Alexendoo commented on Mar 8, 2023

matthiaskrgr commented on Mar 22, 2024

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