useless_attribute: allow dead_code

Closes rust-lang/rust-clippy#4467

Author: 9999years

clippy_lints/src/attrs/useless_attribute.rs

@@ -26,6 +26,7 @@ pub(super) fn check(cx: &LateContext<'_>, item: &Item<'_>, attrs: &[Attribute])
                                 || is_word(lint, sym!(unused))
                                 || is_word(lint, sym!(unused_import_braces))
                                 || is_word(lint, sym!(unused_braces))
+                                || is_word(lint, sym!(dead_code))
                                 || extract_clippy_lint(lint).map_or(false, |s| {
                                     matches!(
                                         s.as_str(),

tests/ui/useless_attribute.fixed

@@ -92,3 +92,7 @@ use module::{Struct};
 fn main() {
     test_indented_attr();
 }
+
+// Regression test for https://github.com/rust-lang/rust-clippy/issues/4467
+#[allow(dead_code)]
+use std::collections as puppy_doggy;

tests/ui/useless_attribute.rs

@@ -92,3 +92,7 @@ use module::{Struct};
 fn main() {
     test_indented_attr();
 }
+
+// Regression test for https://github.com/rust-lang/rust-clippy/issues/4467
+#[allow(dead_code)]
+use std::collections as puppy_doggy;