Incorrect handling of rustc_on_unimplemented for duplicated_attributes

[Noratrieb]

Summary

I ran clippy on the standard library and it complained about duplicated attributes that were not duplicated.
This does not affect the new diagnostic::on_unimplemented attribute, as it does not support on syntax.

Lint Name

duplicated_attributes

Reproducer

I tried this code:

#![feature(rustc_attrs)]

#[rustc_on_unimplemented(
    on(
        _Self = "&str",
        label = "`{Self}` is not an iterator; try calling `.chars()` or `.bytes()`"
    ),
    on(
        _Self = "alloc::string::String",
        label = "`{Self}` is not an iterator; try calling `.chars()` or `.bytes()`"
    ),
)]
trait X {}

fn main() {}

I saw this happen:

warning: duplicated attribute
  --> uwuclip.rs:10:9
   |
10 |         label = "`{Self}` is not an iterator; try calling `.chars()` or `.bytes()`"
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: first defined here
  --> uwuclip.rs:6:9
   |
6  |         label = "`{Self}` is not an iterator; try calling `.chars()` or `.bytes()`"
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: remove this attribute
  --> uwuclip.rs:10:9
   |
10 |         label = "`{Self}` is not an iterator; try calling `.chars()` or `.bytes()`"
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#duplicated_attributes
   = note: `#[warn(clippy::duplicated_attributes)]` on by default

I expected to see this happen:
No lints, this is some excellent code straight from the standard library

Version

rustc 1.79.0-nightly (8df7e723e 2024-03-30)
binary: rustc
commit-hash: 8df7e723ea729a7f917501cc2d91d640b7021373
commit-date: 2024-03-30
host: x86_64-unknown-linux-gnu
release: 1.79.0-nightly
LLVM version: 18.1.2

Additional Labels

No response