const_if_match ICE

[DutchGhost]

The following code ICE's on beta and nightly, (notice how I DIDN'T use the ``#![feature(const_if_match)]` feature)

struct Bug {
    inner: [(); match || {1} {
        n => n(),
    }],
}

Backtrace:

 Compiling playground v0.0.1 (/playground)
error[E0658]: `match` is not allowed in a `const`
 --> src/lib.rs:2:17
  |
2 |       inner: [(); match || {1} {
  |  _________________^
3 | |         n => n(),
4 | |     }],
  | |_____^
  |
  = note: for more information, see https://github.com/rust-lang/rust/issues/49146
  = help: add `#![feature(const_if_match)]` to the crate attributes to enable

error[E0015]: calls in constants are limited to constant functions, tuple structs and tuple variants
 --> src/lib.rs:3:14
  |
3 |         n => n(),
  |              ^^^

error: internal compiler error: src/librustc_typeck/collect.rs:1869: to get the signature of a closure, use `closure_sig()` not `fn_sig()`

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:892:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:84
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:61
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1025
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1426
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:65
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:50
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:193
   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:475
  12: std::panicking::begin_panic
  13: rustc_errors::HandlerInner::bug
  14: rustc_errors::Handler::bug
  15: rustc::util::bug::opt_span_bug_fmt::{{closure}}
  16: rustc::ty::context::tls::with_opt::{{closure}}
  17: rustc::ty::context::tls::with_opt
  18: rustc::util::bug::opt_span_bug_fmt
  19: rustc::util::bug::bug_fmt
  20: rustc_typeck::collect::fn_sig
  21: rustc::ty::query::__query_compute::fn_sig
  22: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::fn_sig>::compute
  23: rustc::dep_graph::graph::DepGraph::with_task_impl
  24: rustc_rayon_core::tlv::with
  25: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  26: rustc::ty::constness::provide::is_const_fn_raw
  27: rustc::ty::query::__query_compute::is_const_fn_raw
  28: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::is_const_fn_raw>::compute
  29: rustc::dep_graph::graph::DepGraph::with_task_impl
  30: rustc_rayon_core::tlv::with
  31: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  32: <rustc_mir::const_eval::CompileTimeInterpreter as rustc_mir::interpret::machine::Machine>::find_mir_or_eval_fn
  33: rustc_mir::interpret::terminator::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_fn_call
  34: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::step
  35: rustc_mir::const_eval::const_eval_raw_provider
  36: rustc::ty::query::__query_compute::const_eval_raw
  37: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::const_eval_raw>::compute
  38: rustc::dep_graph::graph::DepGraph::with_task_impl
  39: rustc_rayon_core::tlv::with
  40: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  41: rustc_mir::const_eval::const_eval_provider
  42: rustc::ty::query::__query_compute::const_eval
  43: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::const_eval>::compute
  44: rustc::dep_graph::graph::DepGraph::with_task_impl
  45: rustc_rayon_core::tlv::with
  46: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  47: rustc_mir::const_eval::const_eval_provider
  48: rustc::ty::query::__query_compute::const_eval
  49: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::const_eval>::compute
  50: rustc::dep_graph::graph::DepGraph::with_task_impl
  51: rustc_rayon_core::tlv::with
  52: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  53: rustc::ty::sty::Const::eval::{{closure}}
  54: <rustc::traits::project::AssocTypeNormalizer as rustc::ty::fold::TypeFolder>::fold_const
  55: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::TyS>::super_fold_with
  56: <rustc::traits::project::AssocTypeNormalizer as rustc::ty::fold::TypeFolder>::fold_ty
  57: rustc::traits::project::normalize
  58: rustc_typeck::check::FnCtxt::normalize_associated_types_in
  59: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  60: rustc_rayon_core::tlv::with
  61: rustc::ty::context::GlobalCtxt::enter_local
  62: rustc_typeck::check::wfcheck::check_item_well_formed
  63: rustc::ty::query::__query_compute::check_item_well_formed
  64: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::check_item_well_formed>::compute
  65: rustc::dep_graph::graph::DepGraph::with_task_impl
  66: rustc_rayon_core::tlv::with
  67: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  68: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::ensure_query
  69: rustc_rayon::iter::plumbing::Producer::fold_with
  70: rustc_rayon::iter::plumbing::bridge_producer_consumer::helper
  71: rustc_rayon_core::job::StackJob<L,F,R>::run_inline
  72: rustc_rayon_core::registry::in_worker
  73: rustc_rayon::iter::plumbing::bridge_producer_consumer::helper
  74: std::panicking::try::do_call
  75: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:78
  76: <rustc_rayon_core::job::StackJob<L,F,R> as rustc_rayon_core::job::Job>::execute
  77: rustc_rayon_core::registry::WorkerThread::wait_until_cold
  78: rustc_rayon_core::registry::ThreadBuilder::run
  79: scoped_tls::ScopedKey<T>::set
  80: std::thread::local::LocalKey<T>::with
  81: scoped_tls::ScopedKey<T>::set
  82: crossbeam_utils::thread::ScopedThreadBuilder::spawn::{{closure}}
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 1.41.0-nightly (3ed3b8bb7 2019-12-17) 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 [fn_sig] processing `Bug::inner::{{constant}}#0::{{closure}}#0`
#1 [is_const_fn_raw] checking if item is const fn: `Bug::inner::{{constant}}#0::{{closure}}#0`
#2 [const_eval_raw] const-evaluating `Bug::inner::{{constant}}#0`
#3 [const_eval] const-evaluating + checking `Bug::inner::{{constant}}#0`
#4 [const_eval] const-evaluating + checking `Bug::inner::{{constant}}#0`
#5 [check_item_well_formed] processing `Bug`
#6 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0015, E0658.
For more information about an error, try `rustc --explain E0015`.
error: could not compile `playground`.

[estebank]

I believe it might have been introduced by #66866

CC @oli-obk

[hellow554]

This is a regression from stable to beta as well.

[oli-obk]

Ugh, typeck failing does not mean const eval won't run. I guess we need more tainted_by_errors (https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty/struct.TypeckTables.html#structfield.tainted_by_errors) checks everywhere.

[pnkfelix]

triage: P-high. Leaving nominated.

[pnkfelix]

discussed in T-compiler meeting. Downgrading to P-medium

[Alexendoo]

Fixed by #68563