warning: empty trait list in derive should not emit if created by a macro

[Havvy]

The following code should not emit a warning at the call site of the macro:

#![crate_type="lib"]

macro_rules! ds {
    () => (#[derive()] struct StructDs;)
}

ds!{}

Currently, it does:

warning: empty trait list in `derive`
  --> src/lib.rs:8:12
   |
8  |     () => (#[derive()] struct StructDs;)
   |            ^^^^^^^^^^^
...
11 | ds!{}
   | ----- in this macro invocation

[fmease]

Since #79078, #[derive()] no longer triggers a lint anywhere / at all. Closing as (coincidentally) fixed.