Fix compilation errors in collections-contrib

Author: julienrf

src/main/scala/strawman/collection/immutable/MultiMap.scala

@@ -74,7 +74,7 @@ object MultiMap extends MapFactory[MultiMap] {
 
   def newBuilder[K, V](): Builder[(K, V), MultiMap[K, V]] =
     new ImmutableBuilder[(K, V), MultiMap[K, V]](empty[K, V]) {
-      def add(elem: (K, V)): this.type = { elems = elems + elem; this }
+      def addOne(elem: (K, V)): this.type = { elems = elems + elem; this }
     }
 
 }

src/main/scala/strawman/collection/immutable/MultiSet.scala

@@ -63,7 +63,7 @@ object MultiSet extends IterableFactory[MultiSet] {
 
   def newBuilder[A](): Builder[A, MultiSet[A]] =
     new ImmutableBuilder[A, MultiSet[A]](empty[A]) {
-      def add(elem: A): this.type = { elems = elems + elem; this }
+      def addOne(elem: A): this.type = { elems = elems + elem; this }
     }
 
 }

src/main/scala/strawman/collection/immutable/SortedMultiMap.scala

@@ -78,7 +78,7 @@ object SortedMultiMap extends SortedMapFactory[SortedMultiMap] {
 
   def newBuilder[K: Ordering, V](): Builder[(K, V), SortedMultiMap[K, V]] =
     new ImmutableBuilder[(K, V), SortedMultiMap[K, V]](empty[K, V]) {
-      def add(elem: (K, V)): this.type = { elems = elems + elem; this }
+      def addOne(elem: (K, V)): this.type = { elems = elems + elem; this }
     }
 
 }

src/main/scala/strawman/collection/immutable/SortedMultiSet.scala

@@ -69,7 +69,7 @@ object SortedMultiSet extends SortedIterableFactory[SortedMultiSet] {
 
   def newBuilder[A: Ordering](): Builder[A, SortedMultiSet[A]] =
     new ImmutableBuilder[A, SortedMultiSet[A]](empty) {
-      def add(elem: A): this.type = { elems = elems + elem; this }
+      def addOne(elem: A): this.type = { elems = elems + elem; this }
     }
 
 }

src/main/scala/strawman/collection/mutable/MultiMap.scala

@@ -22,7 +22,7 @@ class MultiMap[K, V] private (elems: Map[K, Set[V]])
 
   def sets: collection.Map[K, collection.Set[V]] = elems
 
-  def add(elem: (K, V)): this.type = {
+  def addOne(elem: (K, V)): this.type = {
     val (k, v) = elem
     elems.updateWith(k) {
       case None     => Some(Set(v))
@@ -31,7 +31,7 @@ class MultiMap[K, V] private (elems: Map[K, Set[V]])
     this
   }
 
-  def subtract(elem: (K, V)): this.type = {
+  def subtractOne(elem: (K, V)): this.type = {
     val (k, v) = elem
     elems.updateWith(k) {
       case Some(vs) =>

src/main/scala/strawman/collection/mutable/MultiSet.scala

@@ -19,15 +19,15 @@ class MultiSet[A] private (val elems: Map[A, Int])
 
   def occurrences: collection.Map[A, Int] = elems
 
-  def add(elem: A): this.type = {
+  def addOne(elem: A): this.type = {
     elems.updateWith(elem) {
       case None    => Some(1)
       case Some(n) => Some(n + 1)
     }
     this
   }
 
-  def subtract(elem: A): this.type = {
+  def subtractOne(elem: A): this.type = {
     elems.updateWith(elem) {
       case Some(n) => if (n > 1) Some(n - 1) else None
     }

src/main/scala/strawman/collection/mutable/SortedMultiMap.scala

@@ -27,7 +27,7 @@ class SortedMultiMap[K, V] private (elems: SortedMap[K, Set[V]])(implicit val or
   def rangeImpl(from: Option[K], until: Option[K]): SortedMultiMap[K, V] =
     new SortedMultiMap(elems.rangeImpl(from, until))
 
-  def add(elem: (K, V)): this.type = {
+  def addOne(elem: (K, V)): this.type = {
     val (k, v) = elem
     elems.updateWith(k) {
       case None     => Some(Set(v))
@@ -36,7 +36,7 @@ class SortedMultiMap[K, V] private (elems: SortedMap[K, Set[V]])(implicit val or
     this
   }
 
-  def subtract(elem: (K, V)): this.type = {
+  def subtractOne(elem: (K, V)): this.type = {
     val (k, v) = elem
     elems.updateWith(k) {
       case Some(vs) =>

src/main/scala/strawman/collection/mutable/SortedMultiSet.scala

@@ -27,15 +27,15 @@ class SortedMultiSet[A] private (elems: SortedMap[A, Int])(implicit val ordering
   def rangeImpl(from: Option[A], until: Option[A]): SortedMultiSet[A] =
     new SortedMultiSet(elems.rangeImpl(from, until))
 
-  def add(elem: A): this.type = {
+  def addOne(elem: A): this.type = {
     elems.updateWith(elem) {
       case None    => Some(1)
       case Some(n) => Some(n + 1)
     }
     this
   }
 
-  def subtract(elem: A): this.type = {
+  def subtractOne(elem: A): this.type = {
     elems.updateWith(elem) {
       case Some(n) => if (n > 1) Some(n - 1) else None
     }