Use drop instead of the toilet closure |_| ()

src/test/ui/async-await/issues/issue-64433.rs

@@ -23,7 +23,7 @@ impl B {
 async fn can_error(some_string: &str) -> Result<(), String> {
     let a = A { inner: vec![some_string, "foo"] };
     let mut b = B {};
-    Ok(b.something_with_a(a).await.map(|_| ())?)
+    Ok(b.something_with_a(a).await.map(drop)?)
 }
 
 fn main() {

src/test/ui/nll/issue-50343.rs

@@ -3,6 +3,6 @@
 #![deny(unused_mut)]
 
 fn main() {
-    vec![42].iter().map(|_| ()).count();
+    vec![42].iter().map(drop).count();
     vec![(42, 22)].iter().map(|(_x, _y)| ()).count();
 }

src/test/ui/paths-containing-nul.rs

@@ -17,7 +17,7 @@ fn assert_invalid_input<T>(on: &str, result: io::Result<T>) {
                               "{} returned a strange {:?} on a path with NUL", on, e.kind()),
         }
     }
-    inner(on, result.map(|_| ()))
+    inner(on, result.map(drop))
 }
 
 fn main() {