Merge pull request scala/scala#10862 from wangyum/AnyRefMap

Deprecate mutable.AnyRefMap

Author: SethTisue

library/src/scala/collection/generic/IsMap.scala

@@ -75,6 +75,7 @@ object IsMap {
     }
 
   // AnyRefMap has stricter bounds than the ones used by the mapOpsIsMap definition
+  @deprecated("AnyRefMap is deprecated", "2.13.16")
   implicit def anyRefMapIsMap[K0 <: AnyRef, V0]: IsMap[mutable.AnyRefMap[K0, V0]] { type K = K0; type V = V0; type C = mutable.AnyRefMap[K0, V0] } =
     new IsMap[mutable.AnyRefMap[K0, V0]] {
       type K = K0

library/src/scala/collection/mutable/AnyRefMap.scala

@@ -14,6 +14,7 @@ package scala
 package collection
 package mutable
 
+import scala.annotation.meta.companionClass
 import scala.annotation.nowarn
 import scala.collection.generic.DefaultSerializationProxy
 import scala.language.implicitConversions
@@ -41,6 +42,7 @@ import scala.language.implicitConversions
  *  rapidly as 2^30^ is approached.
  *
  */
+@(deprecated @companionClass)("Use `scala.collection.mutable.HashMap` instead for better performance.", since = "2.13.16")
 class AnyRefMap[K <: AnyRef, V] private[collection] (defaultEntry: K => V, initialBufferSize: Int, initBlank: Boolean)
   extends AbstractMap[K, V]
     with MapOps[K, V, Map, AnyRefMap[K, V]]
@@ -521,6 +523,7 @@ class AnyRefMap[K <: AnyRef, V] private[collection] (defaultEntry: K => V, initi
   override protected[this] def stringPrefix = "AnyRefMap"
 }
 
+@deprecated("Use `scala.collection.mutable.HashMap` instead for better performance.", since = "2.13.16")
 object AnyRefMap {
   private final val IndexMask  = 0x3FFFFFFF
   private final val MissingBit = 0x80000000