ICE with anonymous field and a derive in 1.80.1 but also checked on Godbolt's nightly compiler

[tialaramex]

Code

#[derive(Debug)]
pub struct Type
{
    _: u8,
}

Meta

rustc --version --verbose:

rustc 1.80.1 (3f5fd8dd4 2024-08-06) (Fedora 1.80.1-1.fc40)
binary: rustc
commit-hash: 3f5fd8dd41153bc5fdca9427e9e05be2c767ba23
commit-date: 2024-08-06
host: x86_64-unknown-linux-gnu
release: 1.80.1
LLVM version: 18.1.6

Error output

   Compiling ice20240929 v0.1.0 (/home/njl/src/ice20240929)
error[E0658]: unnamed fields are not yet fully implemented
 --> src/main.rs:4:5
  |
4 |     _: u8,
  |     ^
  |
  = note: see issue #49804 <https://github.com/rust-lang/rust/issues/49804> for more information

error[E0601]: `main` function not found in crate `ice20240929`
 --> src/main.rs:5:2
  |
5 | }
  |  ^ consider adding a `main` function to `src/main.rs`

error: struct with unnamed fields must have `#[repr(C)]` representation
 --> src/main.rs:2:1
  |
2 | pub struct Type
  | ^^^^^^^^^^^^^^^ struct `Type` defined here
  |
note: unnamed field defined here
 --> src/main.rs:4:5
  |
4 |     _: u8,
  |     ^^^^^
help: add `#[repr(C)]` to this struct
  |
2 + #[repr(C)]
3 | pub struct Type
  |

error: unnamed fields can only have struct or union types
 --> src/main.rs:4:5
  |
4 |     _: u8,
  |     ^^^^^

thread 'rustc' panicked at compiler/rustc_hir_analysis/src/collect.rs:892:49:
expect Adt for unnamed field
stack backtrace:
   0:     0x7f8f73f4f135 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h2a0cac5be5a8d820
   1:     0x7f8f73f9dafb - core::fmt::write::h17332d03f2f4f35b
   2:     0x7f8f73f4421f - <unknown>
   3:     0x7f8f73f4ef0e - <unknown>
   4:     0x7f8f73f51949 - <unknown>
   5:     0x7f8f73f516ea - std::panicking::default_hook::ha48f87b295834c46
   6:     0x7f8f74a5ec30 - <unknown>
   7:     0x7f8f73f5200b - std::panicking::rust_panic_with_hook::h4eeb081fd329f3e2
   8:     0x7f8f73f51d84 - <unknown>
   9:     0x7f8f73f4f5f9 - <unknown>
  10:     0x7f8f73f51ab7 - rust_begin_unwind
  11:     0x7f8f73f15a73 - core::panicking::panic_fmt::h755ac17b0b090cd9
  12:     0x7f8f73f15a3b - core::option::expect_failed::h27ffe2fb3bb55e8c
  13:     0x7f8f75f9d6c0 - rustc_hir_analysis[9a5fae5dc28e0e53]::collect::find_field
  14:     0x7f8f7710649f - <unknown>
  15:     0x7f8f771058b1 - <unknown>
  16:     0x7f8f754fc093 - <unknown>
  17:     0x7f8f7546323e - <unknown>
  18:     0x7f8f7544390f - <unknown>
  19:     0x7f8f7559f041 - <unknown>
  20:     0x7f8f760a1e57 - <unknown>
  21:     0x7f8f760603dc - <unknown>
  22:     0x7f8f7605d32d - <unknown>
  23:     0x7f8f7605fbc3 - <unknown>
  24:     0x7f8f7605d32d - <unknown>
  25:     0x7f8f7605fbc3 - <unknown>
  26:     0x7f8f760460fa - <unknown>
  27:     0x7f8f7605f589 - <unknown>
  28:     0x7f8f7605d32d - <unknown>
  29:     0x7f8f760d7b02 - <unknown>
  30:     0x7f8f7605d32d - <unknown>
  31:     0x7f8f7612c352 - <unknown>
  32:     0x7f8f76124081 - rustc_hir_typeck[30ee169b06768cb7]::typeck
  33:     0x7f8f768b6ad7 - <unknown>
  34:     0x7f8f75462850 - <unknown>
  35:     0x7f8f75450f11 - <unknown>
  36:     0x7f8f7556d828 - <unknown>
  37:     0x7f8f75fa8e3a - rustc_hir_analysis[9a5fae5dc28e0e53]::check_crate
  38:     0x7f8f76231b9e - rustc_interface[881e2d08a402e036]::passes::analysis
  39:     0x7f8f771081e7 - <unknown>
  40:     0x7f8f75461a4f - <unknown>
  41:     0x7f8f75417c08 - <unknown>
  42:     0x7f8f7555d394 - <unknown>
  43:     0x7f8f76e65fdc - <unknown>
  44:     0x7f8f76e63de7 - <unknown>
  45:     0x7f8f76e68a7a - <unknown>
  46:     0x7f8f73f5bfeb - <unknown>
  47:     0x7f8f73d796d7 - start_thread
  48:     0x7f8f73dfd60c - __clone3
  49:                0x0 - <unknown>

error: 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 1.80.1 (3f5fd8dd4 2024-08-06) (Fedora 1.80.1-1.fc40) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

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

query stack during panic:
#0 [find_field] find the index of maybe nested field `_` in `Type`
#1 [typeck] type-checking `<impl at src/main.rs:1:10: 1:15>::fmt`
end of query stack
Some errors have detailed explanations: E0601, E0658.
For more information about an error, try `rustc --explain E0601`.
error: could not compile `ice20240929` (bin "ice20240929") due to 4 previous errors

thread 'rustc' panicked at compiler/rustc_hir_analysis/src/collect.rs:892:49:
expect Adt for unnamed field

Backtrace

``` 0: 0x7f8f73f4f135 - ::fmt::h2a0cac5be5a8d820 1: 0x7f8f73f9dafb - core::fmt::write::h17332d03f2f4f35b 2: 0x7f8f73f4421f - 3: 0x7f8f73f4ef0e - 4: 0x7f8f73f51949 - 5: 0x7f8f73f516ea - std::panicking::default_hook::ha48f87b295834c46 6: 0x7f8f74a5ec30 - 7: 0x7f8f73f5200b - std::panicking::rust_panic_with_hook::h4eeb081fd329f3e2 8: 0x7f8f73f51d84 - 9: 0x7f8f73f4f5f9 - 10: 0x7f8f73f51ab7 - rust_begin_unwind 11: 0x7f8f73f15a73 - core::panicking::panic_fmt::h755ac17b0b090cd9 12: 0x7f8f73f15a3b - core::option::expect_failed::h27ffe2fb3bb55e8c 13: 0x7f8f75f9d6c0 - rustc_hir_analysis[9a5fae5dc28e0e53]::collect::find_field 14: 0x7f8f7710649f - 15: 0x7f8f771058b1 - 16: 0x7f8f754fc093 - 17: 0x7f8f7546323e - 18: 0x7f8f7544390f - 19: 0x7f8f7559f041 - 20: 0x7f8f760a1e57 - 21: 0x7f8f760603dc - 22: 0x7f8f7605d32d - 23: 0x7f8f7605fbc3 - 24: 0x7f8f7605d32d - 25: 0x7f8f7605fbc3 - 26: 0x7f8f760460fa - 27: 0x7f8f7605f589 - 28: 0x7f8f7605d32d - 29: 0x7f8f760d7b02 - 30: 0x7f8f7605d32d - 31: 0x7f8f7612c352 - 32: 0x7f8f76124081 - rustc_hir_typeck[30ee169b06768cb7]::typeck 33: 0x7f8f768b6ad7 - 34: 0x7f8f75462850 - 35: 0x7f8f75450f11 - 36: 0x7f8f7556d828 - 37: 0x7f8f75fa8e3a - rustc_hir_analysis[9a5fae5dc28e0e53]::check_crate 38: 0x7f8f76231b9e - rustc_interface[881e2d08a402e036]::passes::analysis 39: 0x7f8f771081e7 - 40: 0x7f8f75461a4f - 41: 0x7f8f75417c08 - 42: 0x7f8f7555d394 - 43: 0x7f8f76e65fdc - 44: 0x7f8f76e63de7 - 45: 0x7f8f76e68a7a - 46: 0x7f8f73f5bfeb - 47: 0x7f8f73d796d7 - start_thread 48: 0x7f8f73dfd60c - __clone3 49: 0x0 - ```

[tialaramex]

The ICE does not happen if we don't use a derive, or if we give the field a real name

[clubby789]

Closing since this is a duplicate of #121263 (and related to #121299 and #121161) - the feature is currently up for discussion.