Revert 'isEmpty' transformation

core/builtins/native/kotlin/Collections.kt

@@ -54,7 +54,7 @@ public interface Collection<out E> : Iterable<E> {
     /**
      * Returns `true` if the collection is empty (contains no elements), `false` otherwise.
      */
-    public val isEmpty: Boolean
+    public fun isEmpty(): Boolean
 
     /**
      * Checks if the specified element is contained in this collection.
@@ -129,7 +129,7 @@ public interface MutableCollection<E> : Collection<E>, MutableIterable<E> {
 public interface List<out E> : Collection<E> {
     // Query Operations
     override val size: Int
-    override val isEmpty: Boolean
+    override fun isEmpty(): Boolean
     override fun contains(o: @UnsafeVariance E): Boolean
     override fun iterator(): Iterator<E>
 
@@ -233,7 +233,7 @@ public interface MutableList<E> : List<E>, MutableCollection<E> {
 public interface Set<out E> : Collection<E> {
     // Query Operations
     override val size: Int
-    override val isEmpty: Boolean
+    override fun isEmpty(): Boolean
     override fun contains(o: @UnsafeVariance E): Boolean
     override fun iterator(): Iterator<E>
 
@@ -279,7 +279,7 @@ public interface Map<K, out V> {
     /**
      * Returns `true` if the map is empty (contains no elements), `false` otherwise.
      */
-    public val isEmpty: Boolean
+    public fun isEmpty(): Boolean
 
     /**
      * Returns `true` if the map contains the specified [key].