Add sample for emptySet

libraries/stdlib/samples/test/samples/collections/collections.kt

@@ -257,6 +257,22 @@ class Collections {
         }
     }
 
+    class Sets {
+
+        @Sample
+        fun emptyReadOnlySet() {
+            val set = setOf<String>()
+            assertTrue(set.isEmpty())
+
+            // another way to create an empty set,
+            // type parameter is inferred from the expected type
+            val other: Set<Int> = emptySet()
+
+            assertTrue(set == other, "Empty sets are equal")
+            assertPrints(set, "[]")
+        }
+    }
+
     class Transformations {
 
         @Sample

libraries/stdlib/src/kotlin/collections/Sets.kt

@@ -22,7 +22,10 @@ internal object EmptySet : Set<Nothing>, Serializable {
 }
 
 
-/** Returns an empty read-only set.  The returned set is serializable (JVM). */
+/**
+ * Returns an empty read-only set.  The returned set is serializable (JVM).
+ * @sample samples.collections.Collections.Sets.emptyReadOnlySet
+ */
 public fun <T> emptySet(): Set<T> = EmptySet
 /**
  * Returns a new read-only set with the given elements.
@@ -31,7 +34,10 @@ public fun <T> emptySet(): Set<T> = EmptySet
  */
 public fun <T> setOf(vararg elements: T): Set<T> = if (elements.size > 0) elements.toSet() else emptySet()
 
-/** Returns an empty read-only set.  The returned set is serializable (JVM). */
+/**
+ * Returns an empty read-only set.  The returned set is serializable (JVM).
+ * @sample samples.collections.Collections.Sets.emptyReadOnlySet
+ */
 @kotlin.internal.InlineOnly
 public inline fun <T> setOf(): Set<T> = emptySet()