`min_const_generic` ICE w/ const-argument-non-static-lifetime

[JulianKnodt]

Code

#![feature(min_const_generics)]

fn test<const N: usize>() {}

fn wow<'a>() -> &'a () {
    test::<
        {
            let _: &'a ();
            3
        },
    >();
    &()
}

Meta

Nightly on playground

   Compiling playground v0.0.1 (/playground)
error[E0658]: const generics are unstable
 --> src/lib.rs:3:15
  |
3 | fn test<const N: usize>() {}
  |               ^
  |
  = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
  = help: add `#![feature(const_generics)]` to the crate attributes to enable

error: internal compiler error: src/librustc_mir/borrow_check/universal_regions.rs:768:36: cannot convert `ReEarlyBound(0, 'a)` to a region vid

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:915:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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 1.47.0-nightly (09f4c9f50 2020-08-07) 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

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.
error: could not compile `playground`.

To learn more, run the command again with --verbose.

Backtrace

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:915:9
stack backtrace:
   0: std::backtrace_rs::backtrace::libunwind::trace
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/../../backtrace/src/backtrace/libunwind.rs:96
   1: std::backtrace_rs::backtrace::trace_unsynchronized
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/../../backtrace/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/sys_common/backtrace.rs:77
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/sys_common/backtrace.rs:58
   4: core::fmt::write
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/core/src/fmt/mod.rs:1117
   5: std::io::Write::write_fmt
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/io/mod.rs:1510
   6: std::sys_common::backtrace::_print
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/sys_common/backtrace.rs:61
   7: std::sys_common::backtrace::print
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/sys_common/backtrace.rs:48
   8: std::panicking::default_hook::{{closure}}
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/panicking.rs:198
   9: std::panicking::default_hook
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/panicking.rs:217
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at /rustc/09f4c9f5082f78b0adcee83d3ab4337e000cd28e/library/std/src/panicking.rs:530
  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_mir::borrow_check::universal_regions::UniversalRegionIndices::to_region_vid::{{closure}}
  21: rustc_mir::borrow_check::universal_regions::UniversalRegionIndices::to_region_vid
  22: <rustc_mir::borrow_check::type_check::relate_tys::NllTypeRelatingDelegate as rustc_infer::infer::nll_relate::TypeRelatingDelegate>::push_outlives
  23: <rustc_infer::infer::nll_relate::TypeRelating<D> as rustc_middle::ty::relate::TypeRelation>::regions
  24: rustc_middle::ty::relate::super_relate_tys
  25: rustc_infer::infer::combine::<impl rustc_infer::infer::InferCtxt>::super_combine_tys
  26: rustc_middle::ty::relate::TypeRelation::relate
  27: rustc_mir::borrow_check::type_check::TypeChecker::relate_types
  28: rustc_mir::borrow_check::type_check::type_check
  29: rustc_mir::borrow_check::nll::compute_regions
  30: rustc_mir::borrow_check::do_mir_borrowck
  31: rustc_infer::infer::InferCtxtBuilder::enter
  32: rustc_mir::borrow_check::mir_borrowck
  33: core::ops::function::FnOnce::call_once
  34: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_borrowck_const_arg>::compute
  35: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  36: rustc_data_structures::stack::ensure_sufficient_stack
  37: rustc_query_system::query::plumbing::get_query_impl
  38: rustc_query_system::query::plumbing::ensure_query_impl
  39: rustc_mir::transform::mir_drops_elaborated_and_const_checked
  40: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_drops_elaborated_and_const_checked>::compute
  41: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  42: rustc_data_structures::stack::ensure_sufficient_stack
  43: rustc_query_system::query::plumbing::get_query_impl
  44: rustc_mir::transform::inner_optimized_mir
  45: rustc_mir::transform::optimized_mir_of_const_arg
  46: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::optimized_mir_of_const_arg>::compute
  47: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  48: rustc_data_structures::stack::ensure_sufficient_stack
  49: rustc_query_system::query::plumbing::get_query_impl
  50: rustc_mir::interpret::eval_context::InterpCx<M>::load_mir
  51: rustc_mir::const_eval::eval_queries::const_eval_raw_provider
  52: 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
  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_mir::const_eval::eval_queries::const_eval_validated_provider
  57: 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
  58: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  59: rustc_data_structures::stack::ensure_sufficient_stack
  60: rustc_query_system::query::plumbing::get_query_impl
  61: rustc_mir::const_eval::eval_queries::const_eval_validated_provider
  62: 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
  63: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  64: rustc_data_structures::stack::ensure_sufficient_stack
  65: rustc_query_system::query::plumbing::get_query_impl
  66: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_global_id
  67: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_resolve
  68: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_const
  69: rustc_middle::ty::fold::TypeFoldable::fold_with
  70: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::TyS>::super_fold_with
  71: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  72: rustc_data_structures::stack::ensure_sufficient_stack
  73: rustc_trait_selection::traits::project::normalize
  74: <rustc_infer::infer::InferCtxt as rustc_trait_selection::infer::InferCtxtExt>::partially_normalize_associated_types_in
  75: rustc_typeck::check::FnCtxt::instantiate_value_path
  76: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_kind
  77: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation
  78: rustc_typeck::check::callee::<impl rustc_typeck::check::FnCtxt>::check_call
  79: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_kind
  80: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation
  81: rustc_typeck::check::FnCtxt::check_stmt
  82: rustc_typeck::check::FnCtxt::check_block_with_expected
  83: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_kind
  84: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_expr_with_expectation
  85: rustc_typeck::check::expr::<impl rustc_typeck::check::FnCtxt>::check_return_expr
  86: rustc_typeck::check::check_fn
  87: rustc_infer::infer::InferCtxtBuilder::enter
  88: rustc_typeck::check::typeck
  89: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck>::compute
  90: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  91: rustc_data_structures::stack::ensure_sufficient_stack
  92: rustc_query_system::query::plumbing::get_query_impl
  93: rustc_query_system::query::plumbing::ensure_query_impl
  94: rustc_typeck::check::typeck_item_bodies
  95: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck_item_bodies>::compute
  96: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  97: rustc_data_structures::stack::ensure_sufficient_stack
  98: rustc_query_system::query::plumbing::get_query_impl
  99: rustc_typeck::check_crate
 100: rustc_interface::passes::analysis
 101: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
 102: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
 103: rustc_data_structures::stack::ensure_sufficient_stack
 104: rustc_query_system::query::plumbing::get_query_impl
 105: rustc_interface::passes::QueryContext::enter
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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.47.0-nightly (09f4c9f50 2020-08-07) running on x86_64-unknown-linux-gnu

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

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

query stack during panic:
#0 [mir_borrowck_const_arg] borrow-checking the const argument`wow::{{constant}}#0`
#1 [mir_drops_elaborated_and_const_checked] elaborating drops for `wow::{{constant}}#0`
#2 [optimized_mir_of_const_arg] optimizing MIR for the const argument `wow::{{constant}}#0`
#3 [const_eval_raw] const-evaluating `wow::{{constant}}#0`
#4 [const_eval_validated] const-evaluating + checking `wow::{{constant}}#0`
#5 [const_eval_validated] const-evaluating + checking `wow::{{constant}}#0`
#6 [typeck] type-checking `wow`
#7 [typeck_item_bodies] type-checking all item bodies
#8 [analysis] running analysis passes on this crate
end of query stack

[varkor]

@lcnr pointed out we should forbid lifetimes in anonymous constants to avoid this issue.