#[path] does not accept macro-generated paths

[Nemo157]

I tried this code:

#[path = concat!(env!("OUT_DIR"), "/zbus_xmlgen_output.rs")]
mod generated;

I expected to see this happen: the module is loaded from the expanded path

Instead, this happened:

error: malformed `path` attribute input
 --> src/main.rs:1:1
  |
1 | #[path = concat!(env!("OUT_DIR"), "/zbus_xmlgen_output.rs")]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[path = "file"]`

(Attempted as a workaround for #117464 as zbus-xmlgen generates inner doc attributes).

Meta

rustc --version --verbose:

rustc 1.76.0 (a1a37735c 2023-11-23)
binary: rustc
commit-hash: a1a37735cbc3db359d0b24ba9085c9fcbe1bc274
commit-date: 2023-11-23
host: x86_64-unknown-linux-gnu
release: 1.76.0
LLVM version: 17.0.5

[ehuss]

Thanks for the report! I'm going to close as a duplicate of #87681. I'm not sure how feasible it would be to implement eager expansion in that position due to the way #[path] works during expansion.

[Nemo157]

Ah thanks, I was sure this would have been reported before and spent a while searching but failed to find that issue.