Clean up branching in skip

Author: JulianKnodt

library/core/src/iter/adapters/skip.rs

@@ -1,3 +1,4 @@
+use crate::intrinsics::unlikely;
 use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable};
 use crate::ops::{ControlFlow, Try};
 
@@ -31,13 +32,10 @@ where
 
     #[inline]
     fn next(&mut self) -> Option<I::Item> {
-        if self.n == 0 {
-            self.iter.next()
-        } else {
-            let old_n = self.n;
-            self.n = 0;
-            self.iter.nth(old_n)
+        if unlikely(self.n > 0) {
+            self.iter.nth(crate::mem::take(&mut self.n) - 1);
         }
+        self.iter.next()
     }
 
     #[inline]