Prefer `map(drop)` to `map(|_| ())`

I previously advocated for the latter syntax on stylistic grounds.  But
it generates less efficient code, because it creates a new lambda
function for each usage.  The optimizer does not combine them.  This
change saves about 6KB of code.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/sys/aio.rs b/src/sys/aio.rs
index 3d539821..c54c2e31 100644
--- a/src/sys/aio.rs
+++ b/src/sys/aio.rs
@@ -1138,7 +1138,7 @@ impl<'a> LioCb<'a> {
         let p = self.list.as_ptr();
         Errno::result(unsafe {
             libc::lio_listio(mode as i32, p, self.list.len() as i32, sigevp)
-        }).map(|_| ())
+        }).map(drop)
     }
 
     /// Resubmits any incomplete operations with [`lio_listio`].
@@ -1229,7 +1229,7 @@ impl<'a> LioCb<'a> {
         let p = self.list.as_ptr();
         Errno::result(unsafe {
             libc::lio_listio(mode as i32, p, self.list.len() as i32, sigevp)
-        }).map(|_| ())
+        }).map(drop)
     }
 
     /// Collect final status for an individual `AioCb` submitted as part of an