From 081e2fb747892a7efe12f1e9b0138b9d1726ab6b Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Tue, 20 Oct 2009 19:49:20 +0000
Subject: Fix and test case for #2260.  Hooray for the

ability to influence the priority of implicits.
---
 src/library/scala/Ordered.scala  |  6 +++++-
 src/library/scala/Ordering.scala | 17 ++++++++++++-----
 src/library/scala/Predef.scala   |  4 ----
 test/files/pos/bug2260.scala     | 10 ++++++++++
 4 files changed, 27 insertions(+), 10 deletions(-)
 create mode 100644 test/files/pos/bug2260.scala

diff --git a/src/library/scala/Ordered.scala b/src/library/scala/Ordered.scala
index 009502619c..45e10b3a25 100644
--- a/src/library/scala/Ordered.scala
+++ b/src/library/scala/Ordered.scala
@@ -48,6 +48,10 @@ trait Ordered[A] extends java.lang.Comparable[A] {
   def <= (that: A): Boolean = (this compare that) <= 0
   def >= (that: A): Boolean = (this compare that) >= 0
   def compareTo(that: A): Int = compare(that)
+}
 
-
+object Ordered {
+  /** Lens from Ordering[T] to Ordered[T] */
+  implicit def orderingToOrdered[T](x: T)(implicit ord: Ordering[T]): Ordered[T] =
+    new Ordered[T] { def compare(that: T): Int = ord.compare(x, that) }
 }
diff --git a/src/library/scala/Ordering.scala b/src/library/scala/Ordering.scala
index fed776147f..8b4db3f549 100644
--- a/src/library/scala/Ordering.scala
+++ b/src/library/scala/Ordering.scala
@@ -104,7 +104,18 @@ trait Ordering[T] extends Comparator[T] with PartialOrdering[T] {
   implicit def mkOrderingOps(lhs: T): Ops = new Ops(lhs)
 }
 
-object Ordering {
+/** This would conflict with all the nice implicit Orderings
+ *  available, but thanks to the magic of prioritized implicits
+ *  via subclassing we can make Ordered[A] => Ordering[A] only
+ *  turn up if nothing else works.
+ */
+trait LowPriorityOrderingImplicits {
+  implicit def ordered[A <: Ordered[A]]: Ordering[A] = new Ordering[A] {
+    def compare(x: A, y: A) = x.compare(y)
+  }
+}
+
+object Ordering extends LowPriorityOrderingImplicits {
 
   def apply[T](implicit ord : Ordering[T]) = ord
 
@@ -112,10 +123,6 @@ object Ordering {
     def compare(x: T, y: T) = if (cmp(x, y)) -1 else if (cmp(y, x)) 1 else 0
   }
 
-  def ordered[A <: Ordered[A]]: Ordering[A] = new Ordering[A] {
-    def compare(x: A, y: A) = x.compare(y)
-  }
-
   trait UnitOrdering extends Ordering[Unit] {
     def compare(x: Unit, y: Unit) = 0
   }
diff --git a/src/library/scala/Predef.scala b/src/library/scala/Predef.scala
index 6cb073b173..71fdd64832 100644
--- a/src/library/scala/Predef.scala
+++ b/src/library/scala/Predef.scala
@@ -247,10 +247,6 @@ object Predef extends LowPriorityImplicits {
 
   implicit def exceptionWrapper(exc: Throwable) = new runtime.RichException(exc)
 
-  /** Lens from Ordering[T] to Ordered[T] */
-  implicit def orderingToOrdered[T](x: T)(implicit ord: Ordering[T]): Ordered[T] =
-    new Ordered[T] { def compare(that: T): Int = ord.compare(x, that) }
-
   implicit def byte2short(x: Byte): Short = x.toShort
   implicit def byte2int(x: Byte): Int = x.toInt
   implicit def byte2long(x: Byte): Long = x.toLong
diff --git a/test/files/pos/bug2260.scala b/test/files/pos/bug2260.scala
new file mode 100644
index 0000000000..4e4cc5ab2c
--- /dev/null
+++ b/test/files/pos/bug2260.scala
@@ -0,0 +1,10 @@
+package top
+
+class Text(val value: String) extends Ordered[Text] {
+  def compare(that: Text) = value.compare(that.value)
+}
+
+object Index {
+  import scala.collection.immutable.TreeMap
+  val tree = TreeMap.empty[Text, String]
+}
-- 
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