Check for index-out-of-bound in elementAt function (KT-30051)

libraries/stdlib/common/src/generated/_Arrays.kt

@@ -443,90 +443,63 @@ public operator fun CharArray.contains(element: Char): Boolean {
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun <T> Array<out T>.elementAt(index: Int): T {
-    return get(index)
-}
+public expect fun <T> Array<out T>.elementAt(index: Int): T
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun ByteArray.elementAt(index: Int): Byte {
-    return get(index)
-}
+public expect fun ByteArray.elementAt(index: Int): Byte
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun ShortArray.elementAt(index: Int): Short {
-    return get(index)
-}
+public expect fun ShortArray.elementAt(index: Int): Short
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun IntArray.elementAt(index: Int): Int {
-    return get(index)
-}
+public expect fun IntArray.elementAt(index: Int): Int
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun LongArray.elementAt(index: Int): Long {
-    return get(index)
-}
+public expect fun LongArray.elementAt(index: Int): Long
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun FloatArray.elementAt(index: Int): Float {
-    return get(index)
-}
+public expect fun FloatArray.elementAt(index: Int): Float
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun DoubleArray.elementAt(index: Int): Double {
-    return get(index)
-}
+public expect fun DoubleArray.elementAt(index: Int): Double
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun BooleanArray.elementAt(index: Int): Boolean {
-    return get(index)
-}
+public expect fun BooleanArray.elementAt(index: Int): Boolean
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun CharArray.elementAt(index: Int): Char {
-    return get(index)
-}
+public expect fun CharArray.elementAt(index: Int): Char
 
 /**
  * Returns an element at the given [index] or the result of calling the [defaultValue] function if the [index] is out of bounds of this array.

libraries/stdlib/common/src/generated/_Strings.kt

@@ -20,10 +20,7 @@ import kotlin.random.*
  * 
  * @sample samples.collections.Collections.Elements.elementAt
  */
-@kotlin.internal.InlineOnly
-public inline fun CharSequence.elementAt(index: Int): Char {
-    return get(index)
-}
+public expect fun CharSequence.elementAt(index: Int): Char
 
 /**
  * Returns a character at the given [index] or the result of calling the [defaultValue] function if the [index] is out of bounds of this char sequence.

libraries/stdlib/common/src/generated/_UArrays.kt

@@ -223,10 +223,7 @@ public inline operator fun UShortArray.component5(): UShort {
  */
 @SinceKotlin("1.3")
 @ExperimentalUnsignedTypes
-@kotlin.internal.InlineOnly
-public inline fun UIntArray.elementAt(index: Int): UInt {
-    return get(index)
-}
+public expect fun UIntArray.elementAt(index: Int): UInt
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
@@ -235,10 +232,7 @@ public inline fun UIntArray.elementAt(index: Int): UInt {
  */
 @SinceKotlin("1.3")
 @ExperimentalUnsignedTypes
-@kotlin.internal.InlineOnly
-public inline fun ULongArray.elementAt(index: Int): ULong {
-    return get(index)
-}
+public expect fun ULongArray.elementAt(index: Int): ULong
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
@@ -247,10 +241,7 @@ public inline fun ULongArray.elementAt(index: Int): ULong {
  */
 @SinceKotlin("1.3")
 @ExperimentalUnsignedTypes
-@kotlin.internal.InlineOnly
-public inline fun UByteArray.elementAt(index: Int): UByte {
-    return get(index)
-}
+public expect fun UByteArray.elementAt(index: Int): UByte
 
 /**
  * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
@@ -259,10 +250,7 @@ public inline fun UByteArray.elementAt(index: Int): UByte {
  */
 @SinceKotlin("1.3")
 @ExperimentalUnsignedTypes
-@kotlin.internal.InlineOnly
-public inline fun UShortArray.elementAt(index: Int): UShort {
-    return get(index)
-}
+public expect fun UShortArray.elementAt(index: Int): UShort
 
 /**
  * Returns an element at the given [index] or the result of calling the [defaultValue] function if the [index] is out of bounds of this array.

libraries/stdlib/js/irRuntime/generated/_ArraysJs.kt

@@ -14,6 +14,87 @@ import kotlin.js.*
 import primitiveArrayConcat
 import withType
 
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun <T> Array<out T>.elementAt(index: Int): T {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun ByteArray.elementAt(index: Int): Byte {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun ShortArray.elementAt(index: Int): Short {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun IntArray.elementAt(index: Int): Int {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun LongArray.elementAt(index: Int): Long {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun FloatArray.elementAt(index: Int): Float {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun DoubleArray.elementAt(index: Int): Double {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun BooleanArray.elementAt(index: Int): Boolean {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun CharArray.elementAt(index: Int): Char {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
 /**
  * Returns a [List] that wraps the original array.
  */

libraries/stdlib/js/irRuntime/generated/_StringsJs.kt

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2010-2019 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.text
+
+//
+// NOTE: THIS FILE IS AUTO-GENERATED by the GenerateStandardLib.kt
+// See: https://github.com/JetBrains/kotlin/tree/master/libraries/stdlib
+//
+
+import kotlin.js.*
+
+/**
+ * Returns a character at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this char sequence.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun CharSequence.elementAt(index: Int): Char {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, length: $length}") }
+}
+

libraries/stdlib/js/irRuntime/generated/_UArraysJs.kt

@@ -12,6 +12,50 @@ package kotlin.collections
 
 import kotlin.js.*
 
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+public actual fun UIntArray.elementAt(index: Int): UInt {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+public actual fun ULongArray.elementAt(index: Int): ULong {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+public actual fun UByteArray.elementAt(index: Int): UByte {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+public actual fun UShortArray.elementAt(index: Int): UShort {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
 /**
  * Returns a [List] that wraps the original array.
  */

libraries/stdlib/js/src/generated/_ArraysJs.kt

@@ -14,6 +14,87 @@ import kotlin.js.*
 import primitiveArrayConcat
 import withType
 
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun <T> Array<out T>.elementAt(index: Int): T {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun ByteArray.elementAt(index: Int): Byte {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun ShortArray.elementAt(index: Int): Short {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun IntArray.elementAt(index: Int): Int {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun LongArray.elementAt(index: Int): Long {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun FloatArray.elementAt(index: Int): Float {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun DoubleArray.elementAt(index: Int): Double {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun BooleanArray.elementAt(index: Int): Boolean {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun CharArray.elementAt(index: Int): Char {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
 /**
  * Returns a [List] that wraps the original array.
  */

libraries/stdlib/js/src/generated/_StringsJs.kt

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2010-2019 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.text
+
+//
+// NOTE: THIS FILE IS AUTO-GENERATED by the GenerateStandardLib.kt
+// See: https://github.com/JetBrains/kotlin/tree/master/libraries/stdlib
+//
+
+import kotlin.js.*
+
+/**
+ * Returns a character at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this char sequence.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+public actual fun CharSequence.elementAt(index: Int): Char {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, length: $length}") }
+}
+

libraries/stdlib/js/src/generated/_UArraysJs.kt

@@ -12,6 +12,50 @@ package kotlin.collections
 
 import kotlin.js.*
 
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+public actual fun UIntArray.elementAt(index: Int): UInt {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+public actual fun ULongArray.elementAt(index: Int): ULong {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+public actual fun UByteArray.elementAt(index: Int): UByte {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+public actual fun UShortArray.elementAt(index: Int): UShort {
+    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, size: $size}") }
+}
+
 /**
  * Returns a [List] that wraps the original array.
  */

libraries/stdlib/jvm/src/generated/_ArraysJvm.kt

@@ -14,6 +14,96 @@ package kotlin.collections
 //
 
 
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun <T> Array<out T>.elementAt(index: Int): T {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun ByteArray.elementAt(index: Int): Byte {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun ShortArray.elementAt(index: Int): Short {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun IntArray.elementAt(index: Int): Int {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun LongArray.elementAt(index: Int): Long {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun FloatArray.elementAt(index: Int): Float {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun DoubleArray.elementAt(index: Int): Double {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun BooleanArray.elementAt(index: Int): Boolean {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun CharArray.elementAt(index: Int): Char {
+    return get(index)
+}
+
 /**
  * Returns a list containing all elements that are instances of specified class.
  */

libraries/stdlib/jvm/src/generated/_StringsJvm.kt

@@ -14,6 +14,16 @@ package kotlin.text
 //
 
 
+/**
+ * Returns a character at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this char sequence.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@kotlin.internal.InlineOnly
+public actual inline fun CharSequence.elementAt(index: Int): Char {
+    return get(index)
+}
+
 /**
  * Returns a [SortedSet][java.util.SortedSet] of all characters.
  */

libraries/stdlib/jvm/src/generated/_UArraysJvm.kt

@@ -15,6 +15,54 @@ package kotlin.collections
 //
 
 
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+@kotlin.internal.InlineOnly
+public actual inline fun UIntArray.elementAt(index: Int): UInt {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+@kotlin.internal.InlineOnly
+public actual inline fun ULongArray.elementAt(index: Int): ULong {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+@kotlin.internal.InlineOnly
+public actual inline fun UByteArray.elementAt(index: Int): UByte {
+    return get(index)
+}
+
+/**
+ * Returns an element at the given [index] or throws an [IndexOutOfBoundsException] if the [index] is out of bounds of this array.
+ * 
+ * @sample samples.collections.Collections.Elements.elementAt
+ */
+@SinceKotlin("1.3")
+@ExperimentalUnsignedTypes
+@kotlin.internal.InlineOnly
+public actual inline fun UShortArray.elementAt(index: Int): UShort {
+    return get(index)
+}
+
 /**
  * Returns a [List] that wraps the original array.
  */

libraries/stdlib/test/collections/ArraysTest.kt

@@ -1490,6 +1490,16 @@ class ArraysTest {
         array.sortWith(comparator)
         array.iterator().assertSorted { a, b -> comparator.compare(a, b) <= 0 }
     }
+
+    @Test
+    fun elementAt() {
+        expect(0) { byteArrayOf(0, 1, 2).elementAt(0) }
+        expect(1) { shortArrayOf(0, 1, 2).elementAt(1) }
+        expect(2) { intArrayOf(0, 1, 2).elementAt(2) }
+
+        assertFailsWith<IndexOutOfBoundsException> { arrayOf<String>().elementAt(0) }
+        assertFailsWith<IndexOutOfBoundsException> { longArrayOf(0, 1, 2).elementAt(-1) }
+    }
 }
 
 

libraries/stdlib/test/collections/UnsignedArraysTest.kt

@@ -625,10 +625,8 @@ class UnsignedArraysTest {
         expect(1u) { ushortArrayOf(0, 1, 2).elementAt(1) }
         expect(2u) { uintArrayOf(0, 1, 2).elementAt(2) }
 
-        // TODO: Uncomment these tests after KT-30051 gets fixed.
-        // Currently JS does not throw exception on incorrect index.
-//        assertFailsWith<IndexOutOfBoundsException> { uintArrayOf().elementAt(0) }
-//        assertFailsWith<IndexOutOfBoundsException> { ulongArrayOf(0, 1, 2).elementAt(-1) }
+        assertFailsWith<IndexOutOfBoundsException> { uintArrayOf().elementAt(0) }
+        assertFailsWith<IndexOutOfBoundsException> { ulongArrayOf(0, 1, 2).elementAt(-1) }
     }
 
     @Test

libraries/stdlib/test/text/StringTest.kt

@@ -1460,4 +1460,14 @@ ${"    "}
         assertEquals("  ABC\n   \n  123", "ABC\n   \n123".prependIndent("  "))
         assertEquals("  ", "".prependIndent("  "))
     }
+
+    @Test
+    fun elementAt() {
+        expect('a') { "a c".elementAt(0) }
+        expect(' ') { "a c".elementAt(1) }
+        expect('c') { "a c".elementAt(2) }
+
+        assertFailsWith<IndexOutOfBoundsException> { "".elementAt(0) }
+        assertFailsWith<IndexOutOfBoundsException> { "a c".elementAt(-1) }
+    }
 }

libraries/tools/kotlin-stdlib-gen/src/templates/Elements.kt

@@ -284,6 +284,22 @@ object Elements : TemplateGroupBase() {
             inlineOnly()
             body { "return get(index)" }
         }
+
+        specialFor(CharSequences, ArraysOfObjects, ArraysOfPrimitives, ArraysOfUnsigned) {
+            on(Platform.Common) {
+                inline(Inline.No)
+            }
+            on(Platform.JS) {
+                inline(Inline.No)
+
+                val size = if (f == CharSequences) "length" else "size"
+                body {
+                    """
+                    return elementAtOrElse(index) { throw IndexOutOfBoundsException("index: $index, $size: $$size}") }
+                    """
+                }
+            }
+        }
     }
 
     val f_elementAtOrElse = fn("elementAtOrElse(index: Int, defaultValue: (Int) -> T)") {