Consts + nevertype ICE #61744
Description
Probably one should never write this, and I wonder if it will be disallowed in the future.
Happens on stable, beta and nightly, in all const-forms existing (includes const generics)
pub const unsafe fn fake_type<T>() -> T { hint_unreachable() } #[allow(unconditional_recursion)] pub const unsafe fn hint_unreachable() -> ! { hint_unreachable() } trait Const { const CONSTANT: i32 = unsafe { fake_type() }; } impl <T> Const for T {} pub fn main() -> () { dbg!(i32::CONSTANT); }Backtrace:
Compiling playground v0.0.1 (/playground) thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 0', /rustc/3c235d5600393dfe6c36eeed34042efad8d4f26e/src/libcore/slice/mod.rs:2686:10 note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace. stack backtrace: 0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39 1: std::sys_common::backtrace::_print at src/libstd/sys_common/backtrace.rs:71 2: std::panicking::default_hook::{{closure}} at src/libstd/sys_common/backtrace.rs:59 at src/libstd/panicking.rs:197 3: std::panicking::default_hook at src/libstd/panicking.rs:211 4: rustc::util::common::panic_hook 5: std::panicking::rust_panic_with_hook at src/libstd/panicking.rs:478 6: std::panicking::continue_panic_fmt at src/libstd/panicking.rs:381 7: rust_begin_unwind at src/libstd/panicking.rs:308 8: core::panicking::panic_fmt at src/libcore/panicking.rs:85 9: core::panicking::panic_bounds_check at src/libcore/panicking.rs:61 10: rustc_mir::interpret::eval_context::InterpretCx<M>::layout_of_local 11: rustc_mir::interpret::terminator::<impl rustc_mir::interpret::eval_context::InterpretCx<M>>::eval_fn_call::{{closure}} 12: rustc_mir::interpret::terminator::<impl rustc_mir::interpret::eval_context::InterpretCx<M>>::eval_fn_call 13: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpretCx<M>>::run 14: rustc_mir::const_eval::eval_body_using_ecx 15: rustc_mir::const_eval::const_eval_raw_provider 16: rustc::ty::query::__query_compute::const_eval_raw 17: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::const_eval_raw>::compute 18: rustc::dep_graph::graph::DepGraph::with_task_impl 19: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query 20: rustc_mir::interpret::eval_context::InterpretCx<M>::const_eval_raw 21: rustc_mir::interpret::operand::<impl rustc_mir::interpret::eval_context::InterpretCx<M>>::eval_const_to_op 22: rustc_mir::transform::const_prop::ConstPropagator::eval_constant 23: rustc_mir::transform::const_prop::ConstPropagator::const_prop 24: <rustc_mir::transform::const_prop::ConstPropagator as rustc::mir::visit::Visitor>::visit_statement 25: <rustc_mir::transform::const_prop::ConstProp as rustc_mir::transform::MirPass>::run_pass 26: rustc_mir::transform::run_passes::{{closure}} 27: rustc_mir::transform::run_passes 28: rustc_mir::transform::optimized_mir 29: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::optimized_mir>::compute 30: rustc::dep_graph::graph::DepGraph::with_task_impl 31: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query 32: rustc_mir::monomorphize::collector::collect_items_rec 33: rustc_mir::monomorphize::collector::collect_crate_mono_items::{{closure}} 34: rustc::util::common::time 35: rustc_mir::monomorphize::collector::collect_crate_mono_items 36: rustc::util::common::time 37: rustc_mir::monomorphize::partitioning::collect_and_partition_mono_items 38: rustc::ty::query::__query_compute::collect_and_partition_mono_items 39: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::collect_and_partition_mono_items>::compute 40: rustc::dep_graph::graph::DepGraph::with_task_impl 41: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query 42: rustc_codegen_ssa::base::codegen_crate 43: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_utils::codegen_backend::CodegenBackend>::codegen_crate 44: rustc::util::common::time 45: rustc_interface::passes::start_codegen 46: rustc::ty::context::tls::enter_global 47: rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}} 48: rustc_interface::passes::create_global_ctxt::{{closure}} 49: rustc_interface::passes::BoxedGlobalCtxt::enter 50: rustc_interface::queries::Query<T>::compute 51: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::ongoing_codegen 52: rustc_interface::interface::run_compiler_in_existing_thread_pool 53: std::thread::local::LocalKey<T>::with 54: scoped_tls::ScopedKey<T>::set 55: syntax::with_globals query stack during panic: #0 [const_eval_raw] const-evaluating `Const::CONSTANT` --> src/main.rs:18:10 | 18 | dbg!(i32::CONSTANT); | ^^^^^^^^^^^^^ #1 [optimized_mir] processing `main` #2 [collect_and_partition_mono_items] collect_and_partition_mono_items end of query stack 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 1.35.0 (3c235d560 2019-05-20) running on x86_64-unknown-linux-gnu note: compiler flags: -C opt-level=3 -C codegen-units=1 --crate-type bin note: some of the compiler flags provided by cargo are hidden error: Could not compile `playground`. To learn more, run the command again with --verbose.