include! macro fails if included file has top-level inner attributes

[steveklabnik]

Issue by dwrensha
Sunday Nov 09, 2014 at 14:25 GMT

For earlier discussion, see rust-lang/rust#18810

This issue was labelled with: in the Rust repository

---

// test.rs

pub mod included {
    include!("test_included.rs")
}

fn main() {}

// test_included.rs

#![allow(dead_code)]

pub fn foo() {}

$ rustc test.rs
test_included.rs:3:3: 3:4 error: an inner attribute is not permitted in this context
test_included.rs:3 #![allow(dead_code)]
                     ^
error: aborting due to previous error

I at first thought that the problem was due to the implicit insert of the prelude in the included module. However, adding a #[no_implicit_prelude] attribute does not help.

[SimonSapin]

Is this fixed by https://github.com/rust-lang/meeting-minutes/blob/master/weekly-meetings/2015-01-20.md#goodbye-view-items ?

[dwrensha]

On the latest nightly, I still get the same error (after inserting a semicolon to account for the new macro syntax).

[SirVer]

Future searchers: I stumbled on this issue as I created a generated module in build.rs and rust-lang/rust#18810 contained a work around that helped me.

[peterhuene]

After running into this issue still, I implemented a hacky workaround for this issue with the upcoming procedural macros feature: https://github.com/peterhuene/azure-functions-rs/blob/master/azure-functions-shared-codegen/src/lib.rs

[nixomose]

Future searchers: I stumbled on this issue as I created a generated module in build.rs and rust-lang/rust#18810 contained a work around that helped me.

Future searchers who happen to be rust newbies might be interested to know what you mean by "a work around"
I read the ticket, nothing jumped out at me, and everything I tried failed to yield any result.

I am following this guide for bindgen:
https://rust-lang.github.io/rust-bindgen/tutorial-4.html
and getting this:

error: an inner attribute is not permitted in this context
|
6 | #![allow(non_snake_case)];
| ^^^^^^^^^^^^^^^^^^^^^^^^^

It is hard to google for the difference between #![allow... and #[allow... and although the error explains what the difference between an inner and outer attribute is, it doesn't explain help me understand why the tutorial doesn't work as explained.

[ghost]

It happens yet, are there news about if there will be a solution?

[dwrensha]

I haven't tried it myself, but I think that, starting in rustc 1.54, something like this now works:

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

See https://blog.rust-lang.org/2021/07/29/Rust-1.54.0.html#attributes-can-invoke-function-like-macros

[MingweiSamuel]

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

Unfortunately this doesn't work

Notably, the attributes path, crate_type, and recursion_limit do not support this because they need their values before or during expansion. It is also not supported with proc-macros.

rust-lang/rust#83366 (comment)

[glandium]

It's also worth noting that this also happens if you include!() as the first thing in the crate source itself (e.g. lib.rs or main.rs), and the #[path = concat!(env!("OUT_DIR"), "/foo.rs"] mod foo workaround, even if macros in #[path] worked, couldn't be used.

[DimanNe]

It looks like the issue is still here... I cannot include protobuf generated code, getting a bunch of errors:

error: an inner attribute is not permitted in this context
 --> /home/dimanne/devel/scripts/observability/target/debug/build/input-20af024046742d76/out/generated_with_native/capabilities.rs:6:1
  |
6 | #![allow(unknown_lints)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files
  = note: outer attributes, like `#[test]`, annotate the item following them

[mheese]

@DimanNe as I just came across the same problem, and I saw your comment in the rust-protobuf repo as well, the way out of this is: generate with .gen_mod_rs(true) (should be default since version 3). And then instead of including the module, simply include the generated mod.rs file:

include!(concat!(env!("OUT_DIR"), "/mod.rs"));

I guess the suggested workarounds above are a similar suggestions in nature? unfortunately, this was the only way for me out of this.