Auto merge of #12322 - sanxiyn:expression-with-attribute, r=llogiq

Be careful with expressions with attributes

Fix #9949.

changelog: [`unused_unit`]: skip expressions with attributes

tests/ui/unused_unit.fixed

@@ -94,3 +94,10 @@ mod issue9748 {
         let _ = for<'a> |_: &'a u32| -> () {};
     }
 }
+
+mod issue9949 {
+    fn main() {
+        #[doc = "documentation"]
+        ()
+    }
+}

tests/ui/unused_unit.rs

@@ -94,3 +94,10 @@ fn main() {
         let _ = for<'a> |_: &'a u32| -> () {};
     }
 }
+
+mod issue9949 {
+    fn main() {
+        #[doc = "documentation"]
+        ()
+    }
+}