Clippy error "useless lint attribute" when using FromPrimitive

[dignifiedquire]

Getting this error when running latest clippy on my code, after adding FromPrimitive

error: useless lint attribute
  --> src/packet/tags/sig.rs:15:1
   |
15 | #[derive(FromPrimitive)]
   | ^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#useless_attribute

code is just a simple enum like this

#[derive(FromPrimitive)]
pub enum KeyFlag {
   First = 1,
   Second = 2,
}

• rust version: rustc 1.32.0-nightly (25a42b2ce 2018-11-07)
• clippy version: clippy 0.0.212 (d8b42690 2018-11-04)
• num-derive: 0.2.3

[cuviper]

What it does

Checks for extern crate and use items annotated with lint attributes

I think it's warning about this code in the expansion:

    #[allow(unused_qualifications)]
    extern crate num_traits as _num_traits;

That allow was added for #9, but at the time it was placed on the "dummy" const. It was moved onto this extern crate in #17. I need to make sure of what it was meant to protect exactly -- as-is, the issue-9 test fails on Rust 1.16 through 1.28, but 1.15 and 1.29+ are fine with it.

[athei]

What is necessary to fix this? The "useless lint attribute" is in the correctness category of clips and defaults to deny.

[cuviper]

@athei probably just needs to move the lint back onto the dummy_const.

[cuviper]

Should be fixed by num-derive 0.2.5. Let me know if there's still an issue.

[athei]

Indeed that fixed the warning.