ICE when using associated constant in type

[nbdd0121]

Code

struct X<P,Q>(P,Q);
struct L<T:?Sized>(T);

impl<T:?Sized> L<T>{
    const S: usize=1; 
}

impl<T> X<T,[u8;L::<T>::S]>{
}

Meta

Tested on Playground. Affects both stable and nightly.

Error output

Compiling playground v0.0.1 (/playground)

error: internal compiler error: src/librustc_middle/ty/subst.rs:554:17: type parameter `T/#0` (T/0) out of range when substituting (root type=Some(T)) substs=[]

Backtrace

thhread 'rustc' panicked at 'Box<Any>', /rustc/3503f565e1fb7296983757d2716346f48a4a262b/src/libstd/macros.rs:13:23
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/garden.eu.org-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/garden.eu.org-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:217
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:524
  12: std::panicking::begin_panic
  13: rustc_errors::HandlerInner::span_bug
  14: rustc_errors::Handler::span_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::span_bug_fmt
  20: <rustc_middle::ty::subst::SubstFolder as rustc_middle::ty::fold::TypeFolder>::fold_ty
  21: rustc_middle::ty::fold::TypeFoldable::fold_with
  22: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::sty::Const>::super_fold_with
  23: <rustc_middle::ty::subst::SubstFolder as rustc_middle::ty::fold::TypeFolder>::fold_const
  24: rustc_middle::ty::normalize_erasing_regions::<impl rustc_middle::ty::context::TyCtxt>::subst_and_normalize_erasing_regions
  25: rustc_mir::interpret::operand::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_operand
  26: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_rvalue_into_place
  27: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::run
  28: rustc_mir::const_eval::eval_queries::const_eval_raw_provider
  29: 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
  30: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  31: rustc_query_system::query::plumbing::get_query_impl::{{closure}}
  32: rustc_query_system::query::plumbing::get_query_impl
  33: rustc_mir::const_eval::eval_queries::const_eval_validated_provider
  34: 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
  35: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  36: rustc_query_system::query::plumbing::get_query_impl::{{closure}}
  37: rustc_query_system::query::plumbing::get_query_impl
  38: rustc_mir::const_eval::eval_queries::const_eval_validated_provider
  39: 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
  40: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  41: rustc_data_structures::stack::ensure_sufficient_stack
  42: rustc_query_system::query::plumbing::get_query_impl
  43: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_global_id
  44: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_resolve
  45: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_const
  46: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  47: rustc_middle::ty::fold::TypeFoldable::fold_with
  48: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  49: rustc_trait_selection::traits::project::normalize
  50: <rustc_infer::infer::InferCtxt as rustc_trait_selection::infer::InferCtxtExt>::partially_normalize_associated_types_in
  51: rustc_infer::infer::InferCtxtBuilder::enter
  52: rustc_typeck::check::wfcheck::check_item_well_formed
  53: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::check_item_well_formed>::compute
  54: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  55: rustc_data_structures::stack::ensure_sufficient_stack
  56: rustc_query_system::query::plumbing::get_query_impl
  57: rustc_query_system::query::plumbing::ensure_query_impl
  58: <rustc_typeck::check::wfcheck::CheckTypeWellFormedVisitor as rustc_hir::itemlikevisit::ParItemLikeVisitor>::visit_item
  59: rustc_data_structures::sync::par_for_each_in
  60: rustc_hir::hir::Crate::par_visit_all_item_likes
  61: rustc_session::session::Session::track_errors
  62: rustc_typeck::check_crate
  63: rustc_interface::passes::analysis
  64: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  65: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  66: rustc_data_structures::stack::ensure_sufficient_stack
  67: rustc_query_system::query::plumbing::get_query_impl
  68: rustc_middle::ty::context::tls::enter_global
  69: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  70: rustc_span::with_source_map
  71: rustc_interface::interface::run_compiler_in_existing_thread_pool
  72: scoped_tls::ScopedKey<T>::set
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 1.46.0-nightly (3503f565e 2020-07-02) 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 [const_eval_raw] const-evaluating `X::<T, [u8; _]>::{{constant}}#0`
#1 [const_eval_validated] const-evaluating + checking `X::<T, [u8; _]>::{{constant}}#0`
#2 [const_eval_validated] const-evaluating + checking `X::<T, [u8; _]>::{{constant}}#0`
#3 [check_item_well_formed] checking that `X<T, [u8; _]>` is well-formed
#4 [analysis] running analysis passes on this crate
end of query stack

[DutchGhost]

The ice message itself is a dupe of #71202, #69239, #67375 and probably a few more

[JohnTitor]

godbolt says it regressed since 1.22.0: https://rust.godbolt.org/z/UrrpoH

[lcnr]

This is blocked on lazy normalization of constants, see #72219 for more details.

[LeSeulArtichaut]

Assigning P-medium as discussed as part of the Prioritization WG procedure.

[JohnTitor]

Triage: This now emits a normal error about const_generics and compiles fine with #![feature(const_generics)] on the latest nightly: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=98d8e97584b3e13c1af81b3240f29950

[lcnr]

we already have quite a few similar tests here, closing without adding an additional one