JVM IR: allow custom toArray to have any array type

To avoid breaking Java source compatibility. This problem can be fixed
later once JVM IR is stabilized.

 #KT-43111 Fixed

compiler/testData/codegen/box/toArray/toArrayFromJava.kt

@@ -1,6 +1,4 @@
 // TARGET_BACKEND: JVM
-// The old backend thinks `toArray(): Array<Int?>` is the same as `toArray(): Array<Any?>`
-// IGNORE_BACKEND: JVM
 // WITH_RUNTIME
 // FILE: MyListWithCustomToArray.java
 
@@ -29,7 +27,7 @@ class MyListSubclass<T>(val list: List<T>): MyListWithCustomToArray<T>() {
         get() = list.size
 }
 
-class MyCollection<T>(val list: List<T>) : Collection<T> by list {
+class MyCollectionWithCustomIntToArray<T>(val list: List<T>) : Collection<T> by list {
     fun toArray(): Array<Int?> =
         arrayOfNulls<Int>(0)
 }
@@ -43,8 +41,13 @@ fun box(): String {
     list2.toArray().contentToString().let { if (it != "[null]") return "fail 3: $it" }
     list2.toArray(arrayOfNulls<Int>(1)).contentToString().let { if (it != "[null]") return "fail 4: $it" }
 
-    val list3 = MyCollection(listOf(2, 3, 9)) as java.util.Collection<*>
+    val list3 = MyCollectionWithCustomIntToArray(listOf(2, 3, 9)) as java.util.Collection<*>
+    /*
+    // This fails with AbstractMethodError at the moment because of a bug where the backend doesn't check the array element type
+    // of the return type when looking for an implementation of the non-generic parameterless `toArray`.
+    // See `FunctionDescriptor.isNonGenericToArray`, `IrSimpleFunction.isNonGenericToArray` and KT-43111.
     list3.toArray().contentToString().let { if (it != "[2, 3, 9]") return "fail 5: $it" }
     list3.toArray(arrayOfNulls<Int>(0)).contentToString().let { if (it != "[2, 3, 9]") return "fail 6: $it" }
+     */
     return "OK"
 }

compiler/testData/codegen/bytecodeListing/collectionStubs/toArray/customNonGenericToArray.kt

@@ -0,0 +1,11 @@
+class InternalToArray(d: Collection<Any>): Collection<Any> by d {
+    internal fun toArray(): Array<Int> = null!!
+}
+
+class PrivateToArray(d: Collection<Any>): Collection<Any> by d {
+    private fun toArray(): Array<Int> = null!!
+}
+
+class PublicToArray(d: Collection<Any>): Collection<Any> by d {
+    public fun toArray(): Array<Int> = null!!
+}

compiler/testData/codegen/bytecodeListing/collectionStubs/toArray/customNonGenericToArray.txt

@@ -0,0 +1,62 @@
+@kotlin.Metadata
+public final class InternalToArray {
+    // source: 'customNonGenericToArray.kt'
+    private synthetic final field $$delegate_0: java.util.Collection
+    public method <init>(@org.jetbrains.annotations.NotNull p0: java.util.Collection): void
+    public method add(p0: java.lang.Object): boolean
+    public method addAll(p0: java.util.Collection): boolean
+    public method clear(): void
+    public method contains(@org.jetbrains.annotations.NotNull p0: java.lang.Object): boolean
+    public method containsAll(@org.jetbrains.annotations.NotNull p0: java.util.Collection): boolean
+    public method getSize(): int
+    public method isEmpty(): boolean
+    public @org.jetbrains.annotations.NotNull method iterator(): java.util.Iterator
+    public method remove(p0: java.lang.Object): boolean
+    public method removeAll(p0: java.util.Collection): boolean
+    public method retainAll(p0: java.util.Collection): boolean
+    public bridge final method size(): int
+    public final @org.jetbrains.annotations.NotNull method toArray$test_module(): java.lang.Integer[]
+    public method toArray(p0: java.lang.Object[]): java.lang.Object[]
+}
+
+@kotlin.Metadata
+public final class PrivateToArray {
+    // source: 'customNonGenericToArray.kt'
+    private synthetic final field $$delegate_0: java.util.Collection
+    public method <init>(@org.jetbrains.annotations.NotNull p0: java.util.Collection): void
+    public method add(p0: java.lang.Object): boolean
+    public method addAll(p0: java.util.Collection): boolean
+    public method clear(): void
+    public method contains(@org.jetbrains.annotations.NotNull p0: java.lang.Object): boolean
+    public method containsAll(@org.jetbrains.annotations.NotNull p0: java.util.Collection): boolean
+    public method getSize(): int
+    public method isEmpty(): boolean
+    public @org.jetbrains.annotations.NotNull method iterator(): java.util.Iterator
+    public method remove(p0: java.lang.Object): boolean
+    public method removeAll(p0: java.util.Collection): boolean
+    public method retainAll(p0: java.util.Collection): boolean
+    public bridge final method size(): int
+    public final @org.jetbrains.annotations.NotNull method toArray(): java.lang.Integer[]
+    public method toArray(p0: java.lang.Object[]): java.lang.Object[]
+}
+
+@kotlin.Metadata
+public final class PublicToArray {
+    // source: 'customNonGenericToArray.kt'
+    private synthetic final field $$delegate_0: java.util.Collection
+    public method <init>(@org.jetbrains.annotations.NotNull p0: java.util.Collection): void
+    public method add(p0: java.lang.Object): boolean
+    public method addAll(p0: java.util.Collection): boolean
+    public method clear(): void
+    public method contains(@org.jetbrains.annotations.NotNull p0: java.lang.Object): boolean
+    public method containsAll(@org.jetbrains.annotations.NotNull p0: java.util.Collection): boolean
+    public method getSize(): int
+    public method isEmpty(): boolean
+    public @org.jetbrains.annotations.NotNull method iterator(): java.util.Iterator
+    public method remove(p0: java.lang.Object): boolean
+    public method removeAll(p0: java.util.Collection): boolean
+    public method retainAll(p0: java.util.Collection): boolean
+    public bridge final method size(): int
+    public final @org.jetbrains.annotations.NotNull method toArray(): java.lang.Integer[]
+    public method toArray(p0: java.lang.Object[]): java.lang.Object[]
+}

compiler/testData/codegen/bytecodeListing/collectionStubs/toArray/customNonGenericToArray_ir.txt

@@ -0,0 +1,62 @@
+@kotlin.Metadata
+public final class InternalToArray {
+    // source: 'customNonGenericToArray.kt'
+    private synthetic final field $$delegate_0: java.util.Collection
+    public method <init>(@org.jetbrains.annotations.NotNull p0: java.util.Collection): void
+    public method add(p0: java.lang.Object): boolean
+    public method addAll(p0: java.util.Collection): boolean
+    public method clear(): void
+    public method contains(@org.jetbrains.annotations.Nullable p0: java.lang.Object): boolean
+    public method containsAll(@org.jetbrains.annotations.NotNull p0: java.util.Collection): boolean
+    public method getSize(): int
+    public method isEmpty(): boolean
+    public @org.jetbrains.annotations.NotNull method iterator(): java.util.Iterator
+    public method remove(p0: java.lang.Object): boolean
+    public method removeAll(p0: java.util.Collection): boolean
+    public method retainAll(p0: java.util.Collection): boolean
+    public bridge final method size(): int
+    public final @org.jetbrains.annotations.NotNull method toArray(): java.lang.Integer[]
+    public method toArray(p0: java.lang.Object[]): java.lang.Object[]
+}
+
+@kotlin.Metadata
+public final class PrivateToArray {
+    // source: 'customNonGenericToArray.kt'
+    private synthetic final field $$delegate_0: java.util.Collection
+    public method <init>(@org.jetbrains.annotations.NotNull p0: java.util.Collection): void
+    public method add(p0: java.lang.Object): boolean
+    public method addAll(p0: java.util.Collection): boolean
+    public method clear(): void
+    public method contains(@org.jetbrains.annotations.Nullable p0: java.lang.Object): boolean
+    public method containsAll(@org.jetbrains.annotations.NotNull p0: java.util.Collection): boolean
+    public method getSize(): int
+    public method isEmpty(): boolean
+    public @org.jetbrains.annotations.NotNull method iterator(): java.util.Iterator
+    public method remove(p0: java.lang.Object): boolean
+    public method removeAll(p0: java.util.Collection): boolean
+    public method retainAll(p0: java.util.Collection): boolean
+    public bridge final method size(): int
+    public final @org.jetbrains.annotations.NotNull method toArray(): java.lang.Integer[]
+    public method toArray(p0: java.lang.Object[]): java.lang.Object[]
+}
+
+@kotlin.Metadata
+public final class PublicToArray {
+    // source: 'customNonGenericToArray.kt'
+    private synthetic final field $$delegate_0: java.util.Collection
+    public method <init>(@org.jetbrains.annotations.NotNull p0: java.util.Collection): void
+    public method add(p0: java.lang.Object): boolean
+    public method addAll(p0: java.util.Collection): boolean
+    public method clear(): void
+    public method contains(@org.jetbrains.annotations.Nullable p0: java.lang.Object): boolean
+    public method containsAll(@org.jetbrains.annotations.NotNull p0: java.util.Collection): boolean
+    public method getSize(): int
+    public method isEmpty(): boolean
+    public @org.jetbrains.annotations.NotNull method iterator(): java.util.Iterator
+    public method remove(p0: java.lang.Object): boolean
+    public method removeAll(p0: java.util.Collection): boolean
+    public method retainAll(p0: java.util.Collection): boolean
+    public bridge final method size(): int
+    public final @org.jetbrains.annotations.NotNull method toArray(): java.lang.Integer[]
+    public method toArray(p0: java.lang.Object[]): java.lang.Object[]
+}