From bfe9faa637bce1fc499a33beb979ce9dcd35e983 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Fri, 6 May 2016 19:06:57 +0200
Subject: Make Eq contravariant

(and add it to commit set).
---
 src/scala/Eq.scala | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 src/scala/Eq.scala

(limited to 'src/scala')

diff --git a/src/scala/Eq.scala b/src/scala/Eq.scala
new file mode 100644
index 000000000..697ec4318
--- /dev/null
+++ b/src/scala/Eq.scala
@@ -0,0 +1,17 @@
+package scala
+
+/** A marker class indicating that values of kind `T` can be compared. */
+class Eq[-L, -R]
+
+/** Besides being a companion object, this object
+ *  can also be used as a value that's compatible with
+ *  any instance of `Eq`.
+ */
+object Eq extends Eq[Any, Any] {
+
+  /** An implicit that provides an `Eq` instance for all types `T`
+   *  such that `T <: EqClass[T]`.
+   */
+  implicit def eqAny[L, R]: Eq[L, R] = Eq
+}
+
-- 
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