error: Validation error: #[document_signature] can only be used once per item. Remove the duplicate attribute
 --> tests/ui/duplicate_document_signature_fn.rs:8:1
  |
8 | #[document_signature]
  | ^^^^^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in the attribute macro `document_signature` (in Nightly builds, run with -Z macro-backtrace for more info)
