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

[dwrensha]

// 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]

I’ve written a syntax extension (below) to work around this.

mod_path! foo (concat!(env!("OUT_DIR"), "/hello.rs"))

Expands to:

#[path = "path/to/OUT_DIR/hello.rs"]
mod foo;

@alexcrichton I suggest adding this to libsyntax and making it the recommended way to use generated code in Cargo. (#824) Should it go through the RFC process?

#![crate_type="dylib"]
#![feature(plugin_registrar, quote)]

extern crate syntax;
extern crate rustc;

use syntax::codemap::Span;
use syntax::parse::token;
use syntax::ast::{TokenTree, Ident};
use syntax::ext::base::{ExtCtxt, MacResult, DummyResult, MacItems, IdentTT, get_single_str_from_tts};
use rustc::plugin::Registry;

fn expand_mod_path<'a>(cx: &'a mut ExtCtxt, sp: Span, ident: Ident, tts: Vec<TokenTree>)
            -> Box<MacResult + 'a> {
    let path = match get_single_str_from_tts(cx, sp, tts.as_slice(), "mod_path!") {
        Some(string) => string,
        None => return DummyResult::expr(sp),
    };

    MacItems::new(vec![quote_item!(cx,

        #[path = $path]
        mod $ident;

    ).unwrap()].into_iter())
}

#[plugin_registrar]
pub fn plugin_registrar(reg: &mut Registry) {
    reg.register_syntax_extension(token::intern("mod_path"), IdentTT(box expand_mod_path, None));
}

[alexcrichton]

Something like that would definitely need to go through the RFC process, but that seems great to me!

[SimonSapin]

#18849 might be a better solution.

[steveklabnik]

I'm pulling a massive triage effort to get us ready for 1.0. As part of this, I'm moving stuff that's wishlist-like to the RFCs repo, as that's where major new things should get discussed/prioritized.

This issue has been moved to the RFCs repo: rust-lang/rfcs#752

[SimonSapin]

I’ve published the plugin above as a mod_path crate on crates.io