ICE: No entry found for key

[DutchGhost]

The following ICE's on stable only:

struct Bug {
    inner: [(); match Vec::new {
        n => n().len(),
        f @  || @ f => 1
    }],
}

Backtrace:

  Compiling playground v0.0.1 (/playground)
error: expected binding pattern, found `||`
 --> src/lib.rs:6:14
  |
6 |         f @  || @ f => 1
  |              ^^ expected binding pattern

thread 'rustc' panicked at 'no entry found for key', src/libcore/option.rs:1190:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:76
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:60
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1030
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1412
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:64
   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:196
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:210
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:477
  12: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:380
  13: rust_begin_unwind
             at src/libstd/panicking.rs:307
  14: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  15: core::option::expect_failed
             at src/libcore/option.rs:1190
  16: rustc_mir::build::expr::as_place::<impl rustc_mir::build::Builder>::expr_as_place
  17: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  18: rustc_mir::build::expr::as_temp::<impl rustc_mir::build::Builder>::expr_as_temp
  19: rustc_mir::build::expr::as_operand::<impl rustc_mir::build::Builder>::expr_as_operand
  20: rustc_mir::build::expr::as_operand::<impl rustc_mir::build::Builder>::expr_as_operand
  21: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  22: rustc_mir::build::expr::as_temp::<impl rustc_mir::build::Builder>::expr_as_temp
  23: rustc_mir::build::expr::as_place::<impl rustc_mir::build::Builder>::expr_as_place
  24: rustc_mir::build::expr::as_rvalue::<impl rustc_mir::build::Builder>::expr_as_rvalue
  25: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  26: rustc_mir::build::expr::as_temp::<impl rustc_mir::build::Builder>::expr_as_temp
  27: rustc_mir::build::expr::as_operand::<impl rustc_mir::build::Builder>::expr_as_operand
  28: rustc_mir::build::expr::as_operand::<impl rustc_mir::build::Builder>::expr_as_operand
  29: rustc_mir::build::expr::as_operand::<impl rustc_mir::build::Builder>::as_local_operand
  30: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  31: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
  32: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  33: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  34: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  35: rustc_mir::build::scope::<impl rustc_mir::build::Builder>::in_scope
  36: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  37: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  38: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  39: rustc_mir::build::expr::into::<impl rustc_mir::build::Builder>::into_expr
  40: rustc_mir::build::construct_const
  41: rustc::ty::context::tls::with_context::{{closure}}
  42: rustc_mir::build::mir_build
  43: rustc_mir::transform::mir_built
  44: rustc::ty::query::__query_compute::mir_built
  45: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_built>::compute
  46: rustc::dep_graph::graph::DepGraph::with_task_impl
  47: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  48: rustc_mir::transform::check_unsafety::unsafety_check_result
  49: rustc::ty::query::__query_compute::unsafety_check_result
  50: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::unsafety_check_result>::compute
  51: rustc::dep_graph::graph::DepGraph::with_task_impl
  52: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  53: rustc_mir::transform::mir_const
  54: rustc::ty::query::__query_compute::mir_const
  55: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_const>::compute
  56: rustc::dep_graph::graph::DepGraph::with_task_impl
  57: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  58: rustc_mir::transform::qualify_consts::mir_const_qualif
  59: rustc::ty::query::__query_compute::mir_const_qualif
  60: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_const_qualif>::compute
  61: rustc::dep_graph::graph::DepGraph::with_task_impl
  62: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  63: rustc_mir::transform::mir_validated
  64: rustc::ty::query::__query_compute::mir_validated
  65: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_validated>::compute
  66: rustc::dep_graph::graph::DepGraph::with_task_impl
  67: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  68: rustc_mir::borrow_check::mir_borrowck
  69: rustc::ty::query::__query_compute::mir_borrowck
  70: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_borrowck>::compute
  71: rustc::dep_graph::graph::DepGraph::with_task_impl
  72: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  73: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::ensure_query
  74: rustc_mir::transform::optimized_mir
  75: rustc::ty::query::__query_compute::optimized_mir
  76: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::optimized_mir>::compute
  77: rustc::dep_graph::graph::DepGraph::with_task_impl
  78: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  79: rustc_mir::interpret::eval_context::InterpCx<M>::load_mir
  80: rustc_mir::const_eval::const_eval_raw_provider
  81: rustc::ty::query::__query_compute::const_eval_raw
  82: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::const_eval_raw>::compute
  83: rustc::dep_graph::graph::DepGraph::with_task_impl
  84: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  85: rustc_mir::const_eval::const_eval_provider
  86: rustc::ty::query::__query_compute::const_eval
  87: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::const_eval>::compute
  88: rustc::dep_graph::graph::DepGraph::with_task_impl
  89: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  90: rustc_mir::const_eval::const_eval_provider
  91: rustc::ty::query::__query_compute::const_eval
  92: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::const_eval>::compute
  93: rustc::dep_graph::graph::DepGraph::with_task_impl
  94: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  95: rustc::ty::sty::Const::eval
  96: <rustc::traits::project::AssocTypeNormalizer as rustc::ty::fold::TypeFolder>::fold_ty
  97: rustc::traits::project::normalize
  98: rustc_typeck::check::FnCtxt::normalize_associated_types_in
  99: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
 100: rustc::ty::context::GlobalCtxt::enter_local
 101: rustc_typeck::check::wfcheck::check_item_well_formed
 102: rustc::ty::query::__query_compute::check_item_well_formed
 103: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::check_item_well_formed>::compute
 104: rustc::dep_graph::graph::DepGraph::with_task_impl
 105: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.39.0 (4560ea788 2019-11-04) running on x86_64-unknown-linux-gnu

note: compiler flags: -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 [mir_built] processing `Bug::inner::{{constant}}#0`
#1 [unsafety_check_result] processing `Bug::inner::{{constant}}#0`
#2 [mir_const] processing `Bug::inner::{{constant}}#0`
#3 [mir_const_qualif] processing `Bug::inner::{{constant}}#0`
#4 [mir_validated] processing `Bug::inner::{{constant}}#0`
#5 [mir_borrowck] processing `Bug::inner::{{constant}}#0`
#6 [optimized_mir] processing `Bug::inner::{{constant}}#0`
 --> src/lib.rs:4:17
  |
4 |     inner: [(); match Vec::new {
  |                 ^^^^^^^^^^^^^^
#7 [const_eval_raw] const-evaluating `Bug::inner::{{constant}}#0`
#8 [const_eval] const-evaluating + checking `Bug::inner::{{constant}}#0`
#9 [const_eval] const-evaluating + checking `Bug::inner::{{constant}}#0`
#10 [check_item_well_formed] processing `Bug`
#11 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

error: could not compile `playground`.

Might be related to #66742.

[jonas-schievink]

Closing since this does not happen on nightly.