Attach to lib.rs does not notice attributes in lib.rs.

[smj389]

Environment

• IntelliJ Rust plugin version: 0.3.128.3278-202
• Rust toolchain version: 1.47.0-nightly (81dc88f88 2020-08-13) x86_64-pc-windows-msvc
• IDE name and version: CLion 2020.2 (CL-202.6397.106)
• Operating system: Windows 10 10.0

Steps to reproduce

1. Imagine a lib.rs file like this:

#![allow(dead_code)]
#![feature(async_closure)]
mod one;
mod two;

2. Create a new file in the crate, e.g. three.rs
3. Plugin suggests "attach to lib.rs"
4. Get following result:

mod three;

#![allow(dead_code)]
#![feature(async_closure)]
mod one;
mod two;

5. Problem is, of course, that the attributes need to be at the top of the file.
6. 😢

[Undin]

@Kobzol I think it can be fixed together with #5903

Note, we already have similar logic in auto-import quick fix to insert use item. Probably, we can reuse it
See org.rust.ide.utils.import.ImportUtils#firstItem property

[Undin]

@smj389 Thanks for the report!