Merge pull request scala#6915 from MasseGuillaume/bug/10857

Restore collection.Map --, Fixes scala/bug#10957

Author: julienrf

src/library/scala/collection/Map.scala

@@ -288,11 +288,19 @@ trait MapOps[K, +V, +CC[_, _] <: IterableOps[_, AnyConstr, _], +C]
   override def mkString(sep: String): String = super.mkString(sep)
   override def mkString: String = super.mkString
 
-  @deprecated("Consider requiring an immutable Map or fall back to Map.concat", "2.13.0")
-  def + [V1 >: V](kv: (K, V1)): CC[K, V1] = mapFactory.from(new View.Appended(toIterable, kv))
+  @deprecated("Consider requiring an immutable Map or fall back to Map.concat.", "2.13.0")
+  def + [V1 >: V](kv: (K, V1)): CC[K, V1] =
+    mapFactory.from(new View.Appended(toIterable, kv))
 
   @deprecated("Use ++ with an explicit collection argument instead of + with varargs", "2.13.0")
-  def + [V1 >: V](elem1: (K, V1), elem2: (K, V1), elems: (K, V1)*): CC[K, V1] = mapFactory.from(new View.Concat(new View.Appended(new View.Appended(toIterable, elem1), elem2), elems))
+  def + [V1 >: V](elem1: (K, V1), elem2: (K, V1), elems: (K, V1)*): CC[K, V1] =
+    mapFactory.from(new View.Concat(new View.Appended(new View.Appended(toIterable, elem1), elem2), elems))
+
+  @deprecated("Consider requiring an immutable Map.", "2.13.0")
+  @`inline` def -- (keys: IterableOnce[K]): C = {
+    lazy val keysSet = keys.toSet
+    fromSpecificIterable(this.filterKeys(k => !keysSet.contains(k)))
+  }
 }
 
 object MapOps {

src/library/scala/collection/immutable/Map.scala

@@ -76,7 +76,8 @@ trait MapOps[K, +V, +CC[X, +Y] <: MapOps[X, Y, CC, _], +C <: MapOps[K, V, CC, C]
   def removeAll(keys: IterableOnce[K]): C = keys.iterator.foldLeft[C](coll)(_ - _)
 
   /** Alias for `removeAll` */
-  @`inline` final def -- (keys: IterableOnce[K]): C = removeAll(keys)
+  @deprecatedOverriding("This method should be final, but is not due to scala/bug#10853", "2.13.0")
+  /* @`inline` final */ override def -- (keys: IterableOnce[K]): C = removeAll(keys)
 
   /** Creates a new map obtained by updating this map with a given key/value pair.
     *  @param    key the key

test/junit/scala/collection/MapTest.scala

@@ -0,0 +1,27 @@
+package scala.collection
+
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import org.junit.Assert._
+import org.junit.Test
+
+@RunWith(classOf[JUnit4])
+class MapTest {
+  @Test def test: Unit = {
+    val map = collection.Map(
+      1 -> 1,
+      2 -> 2,
+      4 -> 4,
+      5 -> 5
+    )
+
+    val actual = map -- List(1, 2, 3)
+
+    val expected = collection.Map(
+      4 -> 4,
+      5 -> 5
+    )
+
+    assertEquals(expected, actual)
+  }
+}