Custom attr on module causes macro import to be unresolved

[TheDan64]

#![feature(custom_attribute)]

#[my_header = "foo.c"]
pub mod foo {
    use c2rust_bitfields::BitfieldStruct;

    #[derive(BitfieldStruct)]
    struct Foo {
    }
}

will fail to compile with

error: cannot determine resolution for the derive macro `BitfieldStruct`
 --> src/main.rs:7:14
  |
7 |     #[derive(BitfieldStruct)]
  |              ^^^^^^^^^^^^^^
  |
  = note: import resolution is stuck, try simplifying macro imports

error: aborting due to previous error

However, removing the my_header attr will let it compile again.

[Mark-Simulacrum]

cc @petrochenkov

Hm, the custom attribute feature might be at fault here, I suspect you want to make the custom attribute a normal macro (perhaps one that expands to a constant or something, not sure what the use case here is exactly). But this is total guesswork.

[petrochenkov]

#![feature(custom_attribute)] is not supported and slated for removal (with #57921 (comment) being the expected replacement), so I'd close this as wontfix.

[Mark-Simulacrum]

That sounds reasonable. Closing.