ICE while computing layout with uninhabited type

[joshlf]

Code

use core::marker::PhantomData;

pub struct Foo<T: ?Sized, A>(
    PhantomData<(A, T)>,
);

enum Never {}

impl<T: ?Sized> Foo<T, Never> {
    fn new_foo() -> Foo<T, Never> {
        Foo(PhantomData)
    }
}

fn main() {
    let _ = Foo::<(), Never>::new_foo();
    let _ = Foo::<[()], Never>::new_foo(); // <-- This line causes the ICE
}

(playground link)

Meta

Running on the Rust Playground using 1.54.0 stable. Verified that the bug exists in the current beta and stable releases as well.

Error output

Compiling playground v0.0.1 (/playground)
thread 'rustc' panicked at 'assertion failed: layout.abi.is_uninhabited()', compiler/rustc_middle/src/ty/layout.rs:228:21
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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.56.0-nightly (30a0a9b69 2021-08-17) 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 [layout_raw] computing layout of `(Never, [()])`
end of query stack
error: could not compile `playground`

Backtrace

Compiling playground v0.0.1 (/playground)
thread 'rustc' panicked at 'assertion failed: layout.abi.is_uninhabited()', compiler/rustc_middle/src/ty/layout.rs:237:21
stack backtrace:
   0: rust_begin_unwind
             at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:515:5
   1: core::panicking::panic_fmt
             at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/panicking.rs:50:5
   3: rustc_middle::ty::layout::layout_raw
   4: rustc_query_impl::<impl rustc_query_system::query::config::QueryAccessors<rustc_query_impl::plumbing::QueryCtxt> for rustc_query_impl::queries::layout_raw>::compute
   5: rustc_query_system::query::plumbing::get_query_impl
   6: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::layout_raw
   7: <rustc_middle::ty::layout::LayoutCx<rustc_middle::ty::context::TyCtxt> as rustc_target::abi::LayoutOf>::layout_of
   8: <rustc_codegen_llvm::context::CodegenCx as rustc_target::abi::LayoutOf>::spanned_layout_of
   9: rustc_codegen_llvm::debuginfo::metadata::create_struct_stub
  10: rustc_codegen_llvm::debuginfo::metadata::prepare_tuple_metadata
  11: rustc_codegen_llvm::debuginfo::metadata::type_metadata
  12: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
  13: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
  14: rustc_codegen_llvm::debuginfo::metadata::set_members_of_composite_type
  15: rustc_codegen_llvm::debuginfo::metadata::RecursiveTypeDescription::finalize
  16: rustc_codegen_llvm::debuginfo::metadata::type_metadata
  17: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  18: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
  19: rustc_codegen_llvm::debuginfo::metadata::MemberDescriptionFactory::create_member_descriptions
  20: rustc_codegen_llvm::debuginfo::metadata::RecursiveTypeDescription::finalize
  21: rustc_codegen_llvm::debuginfo::metadata::type_metadata
  22: rustc_codegen_llvm::debuginfo::<impl rustc_codegen_ssa::traits::debuginfo::DebugInfoMethods for rustc_codegen_llvm::context::CodegenCx>::dbg_scope_fn::get_containing_scope
  23: rustc_codegen_llvm::debuginfo::<impl rustc_codegen_ssa::traits::debuginfo::DebugInfoMethods for rustc_codegen_llvm::context::CodegenCx>::dbg_scope_fn
  24: rustc_codegen_ssa::mir::codegen_mir
  25: rustc_codegen_ssa::base::codegen_instance
  26: <rustc_middle::mir::mono::MonoItem as rustc_codegen_ssa::mono_item::MonoItemExt>::define
  27: rustc_codegen_llvm::base::compile_codegen_unit::module_codegen
  28: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  29: rustc_codegen_llvm::base::compile_codegen_unit
  30: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  31: rustc_interface::passes::QueryContext::enter
  32: rustc_interface::queries::Queries::ongoing_codegen
  33: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  34: rustc_span::with_source_map
  35: rustc_interface::interface::create_compiler_and_run
  36: scoped_tls::ScopedKey<T>::set
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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.54.0 (a178d0322 2021-07-26) 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 [layout_raw] computing layout of `(Never, [()])`
end of query stack
error: could not compile `playground`

[hkratz]

This bug seems related to debug info generation, it reproduces with rustc --edition=2018 src/main.rs -C debuginfo=2 but not with rustc --edition=2018 src/main.rs -C debuginfo=0 or rustc --edition=2018 src/main.rs -C debuginfo=1.

[hkratz]

$ RUST_BACKTRACE=1 rustc +nightly --edition=2018 src/main.rs --crate-type bin -C debuginfo=2
thread 'rustc' panicked at 'assertion failed: layout.abi.is_uninhabited()', compiler/rustc_middle/src/ty/layout.rs:228:21
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: rustc_middle::ty::layout::layout_raw
   4: rustc_query_system::query::plumbing::get_query_impl
   5: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::layout_raw
   6: <rustc_middle::ty::layout::LayoutCx<rustc_middle::ty::context::TyCtxt> as rustc_target::abi::LayoutOf>::layout_of
   7: rustc_codegen_llvm::debuginfo::metadata::create_struct_stub
   8: rustc_codegen_llvm::debuginfo::metadata::prepare_tuple_metadata
   9: rustc_codegen_llvm::debuginfo::metadata::type_metadata
  10: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
  11: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
  12: rustc_codegen_llvm::debuginfo::metadata::set_members_of_composite_type
  13: rustc_codegen_llvm::debuginfo::metadata::RecursiveTypeDescription::finalize
  14: rustc_codegen_llvm::debuginfo::metadata::type_metadata
  15: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  16: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
  17: rustc_codegen_llvm::debuginfo::metadata::MemberDescriptionFactory::create_member_descriptions
  18: rustc_codegen_llvm::debuginfo::metadata::RecursiveTypeDescription::finalize
  19: rustc_codegen_llvm::debuginfo::metadata::type_metadata
  20: rustc_codegen_llvm::debuginfo::<impl rustc_codegen_ssa::traits::debuginfo::DebugInfoMethods for rustc_codegen_llvm::context::CodegenCx>::dbg_scope_fn::get_containing_scope
  21: rustc_codegen_llvm::debuginfo::<impl rustc_codegen_ssa::traits::debuginfo::DebugInfoMethods for rustc_codegen_llvm::context::CodegenCx>::dbg_scope_fn
  22: rustc_codegen_llvm::debuginfo::<impl rustc_codegen_ssa::traits::debuginfo::DebugInfoMethods for rustc_codegen_llvm::context::CodegenCx>::create_function_debug_context
  23: rustc_codegen_ssa::mir::codegen_mir
  24: rustc_codegen_ssa::base::codegen_instance
  25: <rustc_middle::mir::mono::MonoItem as rustc_codegen_ssa::mono_item::MonoItemExt>::define
  26: rustc_codegen_llvm::base::compile_codegen_unit::module_codegen
  27: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  28: rustc_codegen_llvm::base::compile_codegen_unit
  29: rustc_codegen_ssa::base::codegen_crate
  30: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  31: rustc_interface::queries::Queries::ongoing_codegen
  32: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  33: rustc_span::with_source_map
  34: scoped_tls::ScopedKey<T>::set

[hkratz]

@rustbot label +A-debuginfo