Introduce Any?.hashCode() extension #KT-25039

libraries/stdlib/src/kotlin/util/HashCode.kt

@@ -0,0 +1,18 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin
+
+import kotlin.internal.InlineOnly
+
+
+/**
+ * Returns a hash code value for the object or zero if the object is `null`.
+ *
+ * @see Any.hashCode
+ */
+@SinceKotlin("1.3")
+@InlineOnly
+public inline fun Any?.hashCode(): Int = this?.hashCode() ?: 0

libraries/stdlib/test/utils/HashCodeTest.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package test.utils
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class HashCodeTest {
+    @Test
+    fun hashCodeOfNull() {
+        assertEquals(0, null.hashCode())
+
+        val foo: Any? = null
+        assertEquals(0, foo.hashCode())
+    }
+
+    @Test
+    fun hashCodeOfNotNull() {
+        val value = "test"
+        val nullableValue: String? = value
+
+        assertEquals(value.hashCode(), nullableValue.hashCode())
+    }
+}