ICE with const generics canonicalisation: "assertion failed: !out_value.has_type_flags(TypeFlags::KEEP_IN_LOCAL_TCX)"

[LukasKalbertodt]

I started to further investigate the bug blocking #62959. The following is a minimised test case:

#![feature(const_generics)]

pub struct Foo<T, const N: usize>([T; N]);

impl<T, const N: usize> Foo<T, {N}> {
    pub fn new() -> Self {
        unimplemented!()
    }
}

fn main() {
    let _: Foo<u32, 0> = Foo::new();
}

Results in (with debug assertions enabled):

warning: the feature `const_generics` is incomplete and may cause the compiler to crash
 --> const-bug.rs:1:12
  |
1 | #![feature(const_generics)]
  |            ^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default

thread 'rustc' panicked at 'assertion failed: !out_value.has_type_flags(TypeFlags::KEEP_IN_LOCAL_TCX)', src/librustc/infer/canonical/canonicalizer.rs:548:9
note: run with `RUST_BACKTRACE=1` environment variable to display a 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 1.40.0-dev running on x86_64-unknown-linux-gnu

Here with the backtrace:

warning: the feature `const_generics` is incomplete and may cause the compiler to crash
 --> const-bug.rs:1:12
  |
1 | #![feature(const_generics)]
  |            ^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default

thread 'rustc' panicked at 'assertion failed: !out_value.has_type_flags(TypeFlags::KEEP_IN_LOCAL_TCX)', src/librustc/infer/canonical/canonicalizer.rs:548:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /home/lukas/.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:77
   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:1028
   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: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:189
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:206
  10: <alloc::boxed::Box<F> as core::ops::function::Fn<A>>::call
             at /home/lukas/dev/rust/src/liballoc/boxed.rs:956
  11: rustc_driver::report_ice
             at src/librustc_driver/lib.rs:1188
  12: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:473
  13: std::panicking::begin_panic
             at /home/lukas/dev/rust/src/libstd/panicking.rs:403
  14: rustc::infer::canonical::canonicalizer::Canonicalizer::canonicalize
             at /home/lukas/dev/rust/<::std::macros::panic macros>:3
  15: rustc::infer::canonical::canonicalizer::<impl rustc::infer::InferCtxt>::canonicalize_response
             at /home/lukas/dev/rust/src/librustc/infer/canonical/canonicalizer.rs:93
  16: rustc::infer::canonical::query_response::<impl rustc::infer::InferCtxt>::make_query_response_ignoring_pending_obligations
             at /home/lukas/dev/rust/src/librustc/infer/canonical/query_response.rs:133
  17: rustc_typeck::check::method::probe::<impl rustc_typeck::check::FnCtxt>::probe_op::{{closure}}
             at src/librustc_typeck/check/method/probe.rs:305
  18: rustc::infer::InferCtxt::probe
             at /home/lukas/dev/rust/src/librustc/infer/mod.rs:853
  19: rustc_typeck::check::method::probe::<impl rustc_typeck::check::FnCtxt>::probe_op
             at src/librustc_typeck/check/method/probe.rs:288
  20: rustc_typeck::check::method::probe::<impl rustc_typeck::check::FnCtxt>::probe_for_name
             at src/librustc_typeck/check/method/probe.rs:251
  21: rustc_typeck::check::method::<impl rustc_typeck::check::FnCtxt>::resolve_ufcs
             at src/librustc_typeck/check/method/mod.rs:450
  22: rustc_typeck::check::FnCtxt::resolve_ty_and_res_ufcs
             at src/librustc_typeck/check/mod.rs:3845
  23: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_path
             at src/librustc_typeck/check/expr.rs:472
  24: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_kind
             at src/librustc_typeck/check/expr.rs:243
  25: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation_and_needs
             at src/librustc_typeck/check/expr.rs:173
  26: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation
             at src/librustc_typeck/check/expr.rs:122
  27: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr
             at src/librustc_typeck/check/expr.rs:126
  28: rustc_typeck::check::callee::<impl rustc_typeck::check::FnCtxt>::check_call
             at src/librustc_typeck/check/callee.rs:45
  29: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_kind
             at src/librustc_typeck/check/expr.rs:281
  30: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation_and_needs
             at src/librustc_typeck/check/expr.rs:173
  31: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation
             at src/librustc_typeck/check/expr.rs:122
  32: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_hint
             at src/librustc_typeck/check/expr.rs:114
  33: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_coercable_to_type
             at src/librustc_typeck/check/expr.rs:104
  34: rustc_typeck::check::FnCtxt::check_decl_initializer
             at src/librustc_typeck/check/mod.rs:3897
  35: rustc_typeck::check::FnCtxt::check_decl_local
             at src/librustc_typeck/check/mod.rs:3906
  36: rustc_typeck::check::FnCtxt::check_stmt
             at src/librustc_typeck/check/mod.rs:3955
  37: rustc_typeck::check::FnCtxt::check_block_with_expected::{{closure}}
             at src/librustc_typeck/check/mod.rs:4068
  38: rustc_typeck::check::FnCtxt::with_breakable_ctxt
             at src/librustc_typeck/check/mod.rs:5023
  39: rustc_typeck::check::FnCtxt::check_block_with_expected
             at src/librustc_typeck/check/mod.rs:4066
  40: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_kind
             at src/librustc_typeck/check/expr.rs:278
  41: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation_and_needs
             at src/librustc_typeck/check/expr.rs:173
  42: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation
             at src/librustc_typeck/check/expr.rs:122
  43: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_hint
             at src/librustc_typeck/check/expr.rs:114
  44: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_return_expr
             at src/librustc_typeck/check/expr.rs:688
  45: rustc_typeck::check::check_fn
             at src/librustc_typeck/check/mod.rs:1187
  46: rustc_typeck::check::typeck_tables_of::{{closure}}
             at src/librustc_typeck/check/mod.rs:898
  47: rustc_typeck::check::InheritedBuilder::enter::{{closure}}
             at src/librustc_typeck/check/mod.rs:662
  48: rustc::infer::InferCtxtBuilder::enter::{{closure}}
             at /home/lukas/dev/rust/src/librustc/infer/mod.rs:542
  49: rustc::ty::context::GlobalCtxt::enter_local::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1632
  50: rustc::ty::context::tls::enter_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1854
  51: rustc::ty::context::tls::set_tlv
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1787
  52: rustc::ty::context::tls::enter_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1853
  53: rustc::ty::context::GlobalCtxt::enter_local::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1631
  54: rustc::ty::context::tls::with_related_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1960
  55: rustc::ty::context::tls::with_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1943
  56: rustc::ty::context::tls::with_context_opt
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1932
  57: rustc::ty::context::tls::with_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1943
  58: rustc::ty::context::tls::with_related_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1956
  59: rustc::ty::context::GlobalCtxt::enter_local
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1623
  60: rustc::infer::InferCtxtBuilder::enter
             at /home/lukas/dev/rust/src/librustc/infer/mod.rs:541
  61: rustc_typeck::check::InheritedBuilder::enter
             at src/librustc_typeck/check/mod.rs:662
  62: rustc_typeck::check::typeck_tables_of
             at src/librustc_typeck/check/mod.rs:877
  63: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::typeck_tables_of>::compute::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:942
  64: rustc::ty::query::__query_compute::typeck_tables_of
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:893
  65: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::typeck_tables_of>::compute
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:934
  66: rustc::dep_graph::graph::DepGraph::with_task_impl
             at /home/lukas/dev/rust/src/librustc/dep_graph/graph.rs:322
  67: rustc::dep_graph::graph::DepGraph::with_task
             at /home/lukas/dev/rust/src/librustc/dep_graph/graph.rs:198
  68: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:516
  69: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:248
  70: rustc::ty::context::tls::enter_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1854
  71: rustc::ty::context::tls::set_tlv
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1787
  72: rustc::ty::context::tls::enter_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1853
  73: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:247
  74: rustc::ty::context::tls::with_related_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1960
  75: rustc::ty::context::tls::with_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1943
  76: rustc::ty::context::tls::with_context_opt
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1932
  77: rustc::ty::context::tls::with_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1943
  78: rustc::ty::context::tls::with_related_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1956
  79: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:236
  80: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:508
  81: rustc::ty::query::plumbing::with_diagnostics
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:181
  82: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:507
  83: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:344
  84: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::ensure_query
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:565
  85: rustc::ty::query::TyCtxtEnsure::typeck_tables_of
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:970
  86: rustc_typeck::check::typeck_item_bodies::{{closure}}
             at src/librustc_typeck/check/mod.rs:756
  87: rustc::ty::<impl rustc::ty::context::TyCtxt>::par_body_owners::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/mod.rs:2792
  88: core::iter::traits::iterator::Iterator::for_each::call::{{closure}}
             at /home/lukas/dev/rust/src/libcore/iter/traits/iterator.rs:613
  89: core::iter::traits::iterator::Iterator::fold::ok::{{closure}}
             at /home/lukas/dev/rust/src/libcore/iter/traits/iterator.rs:1813
  90: core::iter::traits::iterator::Iterator::try_fold
             at /home/lukas/dev/rust/src/libcore/iter/traits/iterator.rs:1694
  91: core::iter::traits::iterator::Iterator::fold
             at /home/lukas/dev/rust/src/libcore/iter/traits/iterator.rs:1816
  92: core::iter::traits::iterator::Iterator::for_each
             at /home/lukas/dev/rust/src/libcore/iter/traits/iterator.rs:616
  93: rustc::ty::<impl rustc::ty::context::TyCtxt>::par_body_owners
             at /home/lukas/dev/rust/src/librustc/ty/mod.rs:2791
  94: rustc_typeck::check::typeck_item_bodies
             at src/librustc_typeck/check/mod.rs:755
  95: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::typeck_item_bodies>::compute::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:942
  96: rustc::ty::query::__query_compute::typeck_item_bodies
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:893
  97: rustc::dep_graph::graph::DepGraph::with_task_impl
             at /home/lukas/dev/rust/src/librustc/dep_graph/graph.rs:322
  98: rustc::dep_graph::graph::DepGraph::with_task
             at /home/lukas/dev/rust/src/librustc/dep_graph/graph.rs:198
  99: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:516
 100: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:248
 101: rustc::ty::context::tls::enter_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1854
 102: rustc::ty::context::tls::set_tlv
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1787
 103: rustc::ty::context::tls::enter_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1853
 104: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:247
 105: rustc::ty::context::tls::with_related_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1960
 106: rustc::ty::context::tls::with_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1943
 107: rustc::ty::context::tls::with_context_opt
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1932
 108: rustc::ty::context::tls::with_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1943
 109: rustc::ty::context::tls::with_related_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1956
 110: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:236
 111: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:508
 112: rustc::ty::query::plumbing::with_diagnostics
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:181
 113: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:507
 114: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:344
 115: rustc::ty::query::TyCtxtAt::typeck_item_bodies
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:1019
 116: rustc::ty::query::<impl rustc::ty::context::TyCtxt>::typeck_item_bodies
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:1011
 117: rustc_typeck::check_crate::{{closure}}
             at src/librustc_typeck/lib.rs:343
 118: rustc::util::common::time_ext
             at /home/lukas/dev/rust/src/librustc/util/common.rs:55
 119: rustc::util::common::time
             at /home/lukas/dev/rust/src/librustc/util/common.rs:49
 120: rustc_typeck::check_crate
             at src/librustc_typeck/lib.rs:343
 121: rustc_interface::passes::analysis
             at src/librustc_interface/passes.rs:920
 122: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::analysis>::compute::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:942
 123: rustc::ty::query::__query_compute::analysis
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:893
 124: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::analysis>::compute
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:934
 125: rustc::dep_graph::graph::DepGraph::with_task_impl
             at /home/lukas/dev/rust/src/librustc/dep_graph/graph.rs:322
 126: rustc::dep_graph::graph::DepGraph::with_eval_always_task
             at /home/lukas/dev/rust/src/librustc/dep_graph/graph.rs:374
 127: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:510
 128: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:248
 129: rustc::ty::context::tls::enter_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1854
 130: rustc::ty::context::tls::set_tlv
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1787
 131: rustc::ty::context::tls::enter_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1853
 132: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:247
 133: rustc::ty::context::tls::with_related_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1960
 134: rustc::ty::context::tls::with_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1943
 135: rustc::ty::context::tls::with_context_opt
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1932
 136: rustc::ty::context::tls::with_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1943
 137: rustc::ty::context::tls::with_related_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1956
 138: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:236
 139: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:508
 140: rustc::ty::query::plumbing::with_diagnostics
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:181
 141: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:507
 142: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:344
 143: rustc::ty::query::TyCtxtAt::analysis
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:1019
 144: rustc::ty::query::<impl rustc::ty::context::TyCtxt>::analysis
             at /home/lukas/dev/rust/src/librustc/ty/query/plumbing.rs:1011
 145: rustc_driver::run_compiler::{{closure}}::{{closure}}
             at src/librustc_driver/lib.rs:378
 146: rustc_interface::passes::BoxedGlobalCtxt::enter::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc_interface/passes.rs:814
 147: rustc::ty::context::tls::enter_global::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1886
 148: rustc::ty::context::tls::enter_context::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1854
 149: rustc::ty::context::tls::set_tlv
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1787
 150: rustc::ty::context::tls::enter_context
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1853
 151: rustc::ty::context::tls::enter_global
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1885
 152: rustc_interface::passes::BoxedGlobalCtxt::enter::{{closure}}
             at /home/lukas/dev/rust/src/librustc_interface/passes.rs:814
 153: rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}}
             at /home/lukas/dev/rust/<::rustc_data_structures::box_region::declare_box_region_type macros>:21
 154: rustc_interface::passes::create_global_ctxt::{{closure}}
             at src/librustc_interface/passes.rs:878
 155: alloc::boxed::<impl core::ops::generator::Generator for core::pin::Pin<alloc::boxed::Box<G>>>::resume
             at /home/lukas/dev/rust/src/liballoc/boxed.rs:1093
 156: rustc_data_structures::box_region::PinnedGenerator<I,A,R>::access
             at /home/lukas/dev/rust/src/librustc_data_structures/box_region.rs:52
 157: rustc_interface::passes::BoxedGlobalCtxt::access
             at /home/lukas/dev/rust/<::rustc_data_structures::box_region::declare_box_region_type macros>:24
 158: rustc_interface::passes::BoxedGlobalCtxt::enter
             at /home/lukas/dev/rust/src/librustc_interface/passes.rs:814
 159: rustc_driver::run_compiler::{{closure}}
             at src/librustc_driver/lib.rs:378
 160: rustc_interface::interface::run_compiler_in_existing_thread_pool
             at /home/lukas/dev/rust/src/librustc_interface/interface.rs:117
 161: rustc_interface::interface::run_compiler::{{closure}}
             at /home/lukas/dev/rust/src/librustc_interface/interface.rs:130
 162: rustc_interface::util::spawn_thread_pool::{{closure}}::{{closure}}::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc_interface/util.rs:192
 163: rustc::ty::context::tls::with_thread_locals::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1842
 164: std::thread::local::LocalKey<T>::try_with
             at /home/lukas/dev/rust/src/libstd/thread/local.rs:262
 165: std::thread::local::LocalKey<T>::with
             at /home/lukas/dev/rust/src/libstd/thread/local.rs:239
 166: rustc::ty::context::tls::with_thread_locals::{{closure}}
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1834
 167: std::thread::local::LocalKey<T>::try_with
             at /home/lukas/dev/rust/src/libstd/thread/local.rs:262
 168: std::thread::local::LocalKey<T>::with
             at /home/lukas/dev/rust/src/libstd/thread/local.rs:239
 169: rustc::ty::context::tls::with_thread_locals
             at /home/lukas/dev/rust/src/librustc/ty/context.rs:1826
 170: rustc_interface::util::spawn_thread_pool::{{closure}}::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc_interface/util.rs:192
 171: scoped_tls::ScopedKey<T>::set
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-1.0.0/src/lib.rs:137
 172: rustc_interface::util::spawn_thread_pool::{{closure}}::{{closure}}
             at /home/lukas/dev/rust/src/librustc_interface/util.rs:188
 173: scoped_tls::ScopedKey<T>::set
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-1.0.0/src/lib.rs:137
 174: syntax::with_globals::{{closure}}
             at /home/lukas/dev/rust/src/libsyntax/lib.rs:84
 175: scoped_tls::ScopedKey<T>::set
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-1.0.0/src/lib.rs:137
 176: syntax::with_globals
             at /home/lukas/dev/rust/src/libsyntax/lib.rs:83
 177: rustc_interface::util::spawn_thread_pool::{{closure}}
             at /home/lukas/dev/rust/src/librustc_interface/util.rs:187
 178: rustc_interface::util::scoped_thread::{{closure}}
             at /home/lukas/dev/rust/src/librustc_interface/util.rs:164
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 1.40.0-dev running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck_tables_of] processing `main`
#1 [typeck_item_bodies] type-checking all item bodies
#2 [analysis] running analysis passes on this crate
end of query stack

---

I would love to investigate further, but I am too confused and the panic message doesn't tell me anything useful either. But please tell me if I can do anything else to help you solve the bug. I'd love to have it fixed so that I can continue working on #62959.

CC @varkor @eddyb

[jonas-schievink]

It's this debug assertion that's failing:

rust/src/librustc/infer/canonical/canonicalizer.rs

Lines 545 to 548 in 7bf377f

	// Once we have canonicalized `out_value`, it should not
	// contain anything that ties it to this inference context
	// anymore, so it should live in the global arena.
	debug_assert!(!out_value.has_type_flags(TypeFlags::KEEP_IN_LOCAL_TCX));

Debug assertions are not turned on on released artifacts, but your local config.toml probably has them enabled.

[LukasKalbertodt]

Debug assertions are not turned on on released artifacts, but your local config.toml probably has them enabled.

Ohhh, that explains the weirdness. Should have thought of that myself. Thanks!

But anyway, it's still a bug I assume. And I couldn't find another const generic bug with this error message.

[varkor]

The test case is sufficient with debug assertions (I can reproduce locally). Sorry, I've been meaning to look into this for ages. Having a minimal test case is helpful.