Fix newly added clippy warnings

crossbeam-channel/src/flavors/at.rs

@@ -134,11 +134,7 @@ impl Channel {
     /// Returns the number of messages in the channel.
     #[inline]
     pub(crate) fn len(&self) -> usize {
-        if self.is_empty() {
-            0
-        } else {
-            1
-        }
+        usize::from(!self.is_empty())
     }
 
     /// Returns the capacity of the channel.

crossbeam-channel/src/flavors/tick.rs

@@ -105,11 +105,7 @@ impl Channel {
     /// Returns the number of messages in the channel.
     #[inline]
     pub(crate) fn len(&self) -> usize {
-        if self.is_empty() {
-            0
-        } else {
-            1
-        }
+        usize::from(!self.is_empty())
     }
 
     /// Returns the capacity of the channel.

crossbeam-skiplist/src/base.rs

@@ -1718,7 +1718,7 @@ where
         };
         match (&next_head, &self.tail) {
             // The next key is larger than the latest tail key we observed with this iterator.
-            (Some(ref next), &Some(ref t)) if next.key() >= t.key() => {
+            (Some(ref next), Some(t)) if next.key() >= t.key() => {
                 unsafe {
                     next.node.decrement(guard);
                 }
@@ -1745,7 +1745,7 @@ where
         };
         match (&self.head, &next_tail) {
             // The prev key is smaller than the latest head key we observed with this iterator.
-            (&Some(ref h), Some(next)) if h.key() >= next.key() => {
+            (Some(h), Some(next)) if h.key() >= next.key() => {
                 unsafe {
                     next.node.decrement(guard);
                 }