KT-53154 enumEntries experimental intrinsic stub

Provide an inefficient default implementation and make it "@PublishedApi internal" so it can be safely merged as is.

Intrinsics will be added later in follow-up PRs, and then the implementation will be adjusted accordingly

Merge-request: KT-MR-10843
Merged-by: Vsevolod Tolstopyatov <qwwdfsad@gmail.com>

libraries/stdlib/src/kotlin/enums/EnumEntries.kt

@@ -13,7 +13,7 @@ package kotlin.enums
  * [EnumEntries] contains all enum entries in the order they are declared in the source code,
  * consistently with the corresponding [Enum.ordinal] values.
  *
- * An instance of this interface can only be obtained from `EnumClass.entries` property.
+ * An instance of this interface can be obtained from `EnumClass.entries` property or with [enumEntries] function.
  *
  * #### Implementation note
  * All basic operations, such as `contains` and `indexOf`, are executed in constant time and are likely to be
@@ -23,6 +23,21 @@ package kotlin.enums
 @WasExperimental(ExperimentalStdlibApi::class)
 public sealed interface EnumEntries<E : Enum<E>> : List<E>
 
+/**
+ * Returns [EnumEntries] list containing all enum entries for the given enum type [T].
+ */
+@PublishedApi
+@ExperimentalStdlibApi
+@SinceKotlin("1.9")
+internal inline fun <reified T : Enum<T>> enumEntries(): EnumEntries<T> {
+    /*
+     * Implementation note: this body will be replaced with `throw NotImplementedException()` the moment
+     * all backends starts intrinsifying this call.
+     * Then this method will also be promoted to public.
+     */
+    return enumEntries(enumValues<T>())
+}
+
 @PublishedApi
 @SinceKotlin("1.8") // Used by pre-1.9.0 JVM compiler for the feature in preview mode. Can be safely removed around 2.1
 internal fun <E : Enum<E>> enumEntries(entriesProvider: () -> Array<E>): EnumEntries<E> = EnumEntriesList(entriesProvider())

libraries/stdlib/test/enums/EnumEntriesFactoryTest.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.enums
+
+import kotlin.enums.enumEntries
+import kotlin.test.*
+import test.collections.behaviors.listBehavior
+import test.collections.compare
+import kotlin.enums.EnumEntries
+
+class EnumEntriesFactoryTest {
+
+    enum class EmptyEnum
+
+    enum class NonEmptyEnum {
+        A, B, C
+    }
+
+    @Test
+    fun testEquality() {
+        assertEquals(EmptyEnum.entries, enumEntries())
+        assertEquals(NonEmptyEnum.entries, enumEntries())
+    }
+
+    @Test
+    fun testByCallableReference() {
+        val empty: () -> EnumEntries<EmptyEnum> = ::enumEntries
+        assertEquals(EmptyEnum.entries, empty())
+        val nonEmpty: () -> EnumEntries<NonEmptyEnum> = ::enumEntries
+        assertEquals(NonEmptyEnum.entries, nonEmpty())
+    }
+
+    @Test
+    @Suppress("EnumValuesSoftDeprecate") // For test to avoid comparing entries with entries
+    fun testSanity() {
+        compare(EnumEntriesListTest.EmptyEnum.values().toList(), enumEntries()) { listBehavior() }
+        compare(EnumEntriesListTest.NonEmptyEnum.values().toList(), enumEntries()) { listBehavior() }
+    }
+}