Merge pull request scala/scala#7231 from retronym/merge/2.12.x-to-2.13.x-20180919

Merge 2.12.x to 2.13.x [ci: last-only]

Author: adriaanm

library/src/scala/UninitializedError.scala

@@ -15,4 +15,6 @@ package scala
  *  @author  Martin Odersky
  *  @since   2.5
  */
+// TODO: remove in 2.14
+@deprecated("will be removed in a future release", since = "2.12.7")
 final class UninitializedError extends RuntimeException("uninitialized value")

library/src/scala/collection/mutable/PriorityQueue.scala

@@ -16,6 +16,12 @@ import scala.math.Ordering
   *  To prioritize elements of type A there must be an implicit
   *  Ordering[A] available at creation.
   *
+  *  If multiple elements have the same priority in the ordering of this
+  *  PriorityQueue, no guarantees are made regarding the order in which elements
+  *  are returned by `dequeue` or `dequeueAll`. In particular, that means this
+  *  class does not guarantee first in first out behaviour that may be
+  *  incorrectly inferred from the Queue part of the name of this class.
+  *
   *  Only the `dequeue` and `dequeueAll` methods will return elements in priority
   *  order (while removing elements from the heap).  Standard collection methods
   *  including `drop`, `iterator`, and `toString` will remove or traverse the heap