[stdlib] Gardening: ringBuffer position index

Author: palimondo

stdlib/public/core/Sequence.swift

@@ -901,8 +901,7 @@ extension Sequence {
         ringBuffer.append(element)
       } else {
         ringBuffer[i] = element
-        i += 1
-        i %= maxLength
+        i = (i + 1) % maxLength
       }
     }
 
@@ -978,8 +977,7 @@ extension Sequence {
       } else {
         result.append(ringBuffer[i])
         ringBuffer[i] = element
-        i += 1
-        i %= k
+        i = (i + 1) % k
       }
     }
     return Array(result)