ICE generating debuginfo for non-primitive const generics

[goffrie]

Code

#![feature(const_generics)]
fn shuffle<const IDX: ()>() {}
pub fn foo() {
    shuffle::<{()}>();
}

Playground link

Meta

rustc --version --verbose:

rustc 1.55.0-nightly (b3d11f95c 2021-07-04)
binary: rustc
commit-hash: b3d11f95cc5dd687fdd185ce91e02ebe40e6f46b
commit-date: 2021-07-04
host: x86_64-unknown-linux-gnu
release: 1.55.0-nightly
LLVM version: 12.0.1

This ICE is a regression. Bisection implicates #85269.

Error output

warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
 --> src/lib.rs:1:12
  |
1 | #![feature(const_generics)]
  |            ^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default
  = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information

error: internal compiler error: /rustc/b3d11f95cc5dd687fdd185ce91e02ebe40e6f46b/compiler/rustc_middle/src/ty/consts.rs:195:32: expected bits of (), got Const {
    ty: (),
    val: Value(
        ByRef {
            alloc: Allocation {
                bytes: [],
                relocations: Relocations(
                    SortedMap {
                        data: [],
                    },
                ),
                init_mask: InitMask {
                    blocks: [],
                    len: Size {
                        raw: 0,
                    },
                },
                align: Align {
                    pow2: 0,
                },
                mutability: Not,
                extra: (),
            },
            offset: Size {
                raw: 0,
            },
        },
    ),
}

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1006:9

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 1.55.0-nightly (b3d11f95c 2021-07-04) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 --crate-type lib

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

query stack during panic:
end of query stack
error: aborting due to previous error; 1 warning emitted

error: could not compile `asdf`

Backtrace

stack backtrace:
   0: std::panicking::begin_panic
   1: std::panic::panic_any
   2: rustc_errors::HandlerInner::bug
   3: rustc_errors::Handler::bug
   4: rustc_middle::ty::context::tls::with_opt
   5: rustc_middle::util::bug::opt_span_bug_fmt
   6: rustc_middle::util::bug::bug_fmt
   7: rustc_codegen_ssa::debuginfo::type_names::push_generic_params_internal
   8: rustc_codegen_ssa::debuginfo::type_names::push_generic_params
   9: rustc_codegen_llvm::debuginfo::<impl rustc_codegen_ssa::traits::debuginfo::DebugInfoMethods for rustc_codegen_llvm::context::CodegenCx>::dbg_scope_fn::get_template_parameters
  10: rustc_codegen_llvm::debuginfo::<impl rustc_codegen_ssa::traits::debuginfo::DebugInfoMethods for rustc_codegen_llvm::context::CodegenCx>::dbg_scope_fn
  11: rustc_codegen_ssa::mir::codegen_mir
  12: rustc_codegen_ssa::base::codegen_instance
  13: <rustc_middle::mir::mono::MonoItem as rustc_codegen_ssa::mono_item::MonoItemExt>::define
  14: rustc_codegen_llvm::base::compile_codegen_unit::module_codegen
  15: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  16: rustc_codegen_llvm::base::compile_codegen_unit
  17: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  18: rustc_interface::passes::QueryContext::enter
  19: rustc_interface::queries::Queries::ongoing_codegen
  20: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  21: rustc_span::with_source_map
  22: rustc_interface::interface::create_compiler_and_run
  23: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[goffrie]

This also occurs with types like [u32; 2], causing e.g. packed_simd to break.

[michaelwoerister]

I'll take a look.