optimize mutable.TreeSet#{max, min}

Author: Vadzim Marchanka

library/src/scala/collection/immutable/TreeSet.scala

@@ -150,15 +150,15 @@ final class TreeSet[A] private[immutable] (private[immutable] val tree: RB.Tree[
   override def init = new TreeSet(RB.delete(tree, lastKey))
 
   override def min[A1 >: A](implicit ord: Ordering[A1]): A = {
-    if ((ord eq ordering) && nonEmpty) {
+    if ((ord == ordering) && nonEmpty) {
       head
     } else {
       super.min(ord)
     }
   }
 
   override def max[A1 >: A](implicit ord: Ordering[A1]): A = {
-    if ((ord eq ordering) && nonEmpty) {
+    if ((ord == ordering) && nonEmpty) {
       last
     } else {
       super.max(ord)

library/src/scala/collection/mutable/TreeSet.scala

@@ -104,6 +104,13 @@ sealed class TreeSet[A] private (tree: RB.Tree[A, Null])(implicit val ordering:
   override def last = RB.maxKey(tree).get
   override def lastOption = RB.maxKey(tree)
 
+
+  override def min[B >: A](implicit cmp: Ordering[B]): A =
+    if ((cmp == ordering) && nonEmpty) head else super.min(cmp)
+
+  override def max[B >: A](implicit cmp: Ordering[B]): A =
+    if ((cmp == ordering) && nonEmpty) last else super.max(cmp)
+
   override def foreach[U](f: A => U): Unit = RB.foreachKey(tree, f)
   override def clear(): Unit = RB.clear(tree)