Add -> alias for Tuple2 to Predef

Allow users to pattern match on instances of `Tuple2` with the alternative syntax `key -> value`, in line with the existing alternative syntax for constructing a `Tuple2`.

Author: Jasper-M

library/src/scala/Predef.scala

@@ -167,6 +167,20 @@ object Predef extends LowPriorityImplicits {
  /** @group aliases */
  val Set = immutable.Set
 
+ /**
+ * Allows destructuring tuples with the same syntax as constructing them.
+ *
+ * @example {{{
+ * val tup = "foobar" -> 3
+ *
+ * val c = tup match {
+ * case str -> i => str.charAt(i)
+ * }
+ * }}}
+ * @group aliases
+ */
+ val -> = Tuple2
+
  // Manifest types, companions, and incantations for summoning
  @annotation.implicitNotFound(msg = "No ClassManifest available for ${T}.")
  @deprecated("use `scala.reflect.ClassTag` instead", "2.10.0")