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/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/SyntheticAccessorLowering.kt

@@ -588,7 +588,7 @@ internal class SyntheticAccessorLowering(val context: JvmBackendContext) : IrEle
         if (!withSuper && !declaration.visibility.isPrivate && !declaration.visibility.isProtected) return true
 
         // `toArray` is always accessible cause mapped to public functions
-        if (symbolOwner is IrSimpleFunction && (symbolOwner.isNonGenericToArray(context) || symbolOwner.isGenericToArray(context))) {
+        if (symbolOwner is IrSimpleFunction && (symbolOwner.isNonGenericToArray() || symbolOwner.isGenericToArray(context))) {
             if (symbolOwner.parentAsClass.isCollectionSubClass) {
                 return true
             }

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/ToArrayLowering.kt

@@ -11,8 +11,8 @@ import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
 import org.jetbrains.kotlin.backend.jvm.JvmLoweredDeclarationOrigin
 import org.jetbrains.kotlin.backend.jvm.codegen.isJvmInterface
-import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
+import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.ir.builders.declarations.addDispatchReceiver
 import org.jetbrains.kotlin.ir.builders.declarations.addFunction
 import org.jetbrains.kotlin.ir.builders.declarations.addTypeParameter
@@ -75,7 +75,7 @@ private class ToArrayLowering(private val context: JvmBackendContext) : ClassLow
             }
         }
 
-        irClass.findOrCreate(indirectCollectionSubClass, { it.isNonGenericToArray(context) }) {
+        irClass.findOrCreate(indirectCollectionSubClass, IrSimpleFunction::isNonGenericToArray) {
             irClass.addFunction {
                 name = Name.identifier("toArray")
                 origin = JvmLoweredDeclarationOrigin.TO_ARRAY
@@ -132,7 +132,12 @@ internal fun IrSimpleFunction.isGenericToArray(context: JvmBackendContext): Bool
             returnType.isArrayOrNullableArrayOf(context, typeParameters[0].symbol) &&
             valueParameters[0].type.isArrayOrNullableArrayOf(context, typeParameters[0].symbol)
 
-// Match `fun toArray(): Array<Any?>`
-internal fun IrSimpleFunction.isNonGenericToArray(context: JvmBackendContext): Boolean =
+// Match `fun toArray(): Array<...>`.
+// It would be more correct to check that the return type is erased to `Object[]`, however the old backend doesn't do that
+// (see `FunctionDescriptor.isNonGenericToArray` and KT-43111).
+internal fun IrSimpleFunction.isNonGenericToArray(): Boolean =
     name.asString() == "toArray" && typeParameters.isEmpty() && valueParameters.isEmpty() &&
-            extensionReceiverParameter == null && returnType.isArrayOrNullableArrayOf(context, context.irBuiltIns.anyClass)
+            extensionReceiverParameter == null && returnType.isArrayOrNullableArray()
+
+private fun IrType.isArrayOrNullableArray(): Boolean =
+    this is IrSimpleType && (isArray() || isNullableArray())

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[]
+}

compiler/tests-gen/org/jetbrains/kotlin/codegen/BytecodeListingTestGenerated.java

@@ -174,11 +174,6 @@ public class BytecodeListingTestGenerated extends AbstractBytecodeListingTest {
         runTest("compiler/testData/codegen/bytecodeListing/noRemoveAtInReadOnly.kt");
     }
 
-    @TestMetadata("noToArrayInJava.kt")
-    public void testNoToArrayInJava() throws Exception {
-        runTest("compiler/testData/codegen/bytecodeListing/noToArrayInJava.kt");
-    }
-
     @TestMetadata("privateCompanionFields.kt")
     public void testPrivateCompanionFields() throws Exception {
         runTest("compiler/testData/codegen/bytecodeListing/privateCompanionFields.kt");
@@ -616,6 +611,29 @@ public class BytecodeListingTestGenerated extends AbstractBytecodeListingTest {
                 runTest("compiler/testData/codegen/bytecodeListing/collectionStubs/abstractStubSignatures/stringGenericMutableMap.kt");
             }
         }
+
+        @TestMetadata("compiler/testData/codegen/bytecodeListing/collectionStubs/toArray")
+        @TestDataPath("$PROJECT_ROOT")
+        @RunWith(JUnit3RunnerWithInners.class)
+        public static class ToArray extends AbstractBytecodeListingTest {
+            private void runTest(String testDataFilePath) throws Exception {
+                KotlinTestUtils.runTest(this::doTest, TargetBackend.JVM, testDataFilePath);
+            }
+
+            public void testAllFilesPresentInToArray() throws Exception {
+                KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/bytecodeListing/collectionStubs/toArray"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM, true);
+            }
+
+            @TestMetadata("customNonGenericToArray.kt")
+            public void testCustomNonGenericToArray() throws Exception {
+                runTest("compiler/testData/codegen/bytecodeListing/collectionStubs/toArray/customNonGenericToArray.kt");
+            }
+
+            @TestMetadata("noToArrayInJava.kt")
+            public void testNoToArrayInJava() throws Exception {
+                runTest("compiler/testData/codegen/bytecodeListing/collectionStubs/toArray/noToArrayInJava.kt");
+            }
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/bytecodeListing/coroutines")

compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/IrBytecodeListingTestGenerated.java

@@ -174,11 +174,6 @@ public class IrBytecodeListingTestGenerated extends AbstractIrBytecodeListingTes
         runTest("compiler/testData/codegen/bytecodeListing/noRemoveAtInReadOnly.kt");
     }
 
-    @TestMetadata("noToArrayInJava.kt")
-    public void testNoToArrayInJava() throws Exception {
-        runTest("compiler/testData/codegen/bytecodeListing/noToArrayInJava.kt");
-    }
-
     @TestMetadata("privateCompanionFields.kt")
     public void testPrivateCompanionFields() throws Exception {
         runTest("compiler/testData/codegen/bytecodeListing/privateCompanionFields.kt");
@@ -616,6 +611,29 @@ public class IrBytecodeListingTestGenerated extends AbstractIrBytecodeListingTes
                 runTest("compiler/testData/codegen/bytecodeListing/collectionStubs/abstractStubSignatures/stringGenericMutableMap.kt");
             }
         }
+
+        @TestMetadata("compiler/testData/codegen/bytecodeListing/collectionStubs/toArray")
+        @TestDataPath("$PROJECT_ROOT")
+        @RunWith(JUnit3RunnerWithInners.class)
+        public static class ToArray extends AbstractIrBytecodeListingTest {
+            private void runTest(String testDataFilePath) throws Exception {
+                KotlinTestUtils.runTest(this::doTest, TargetBackend.JVM_IR, testDataFilePath);
+            }
+
+            public void testAllFilesPresentInToArray() throws Exception {
+                KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/bytecodeListing/collectionStubs/toArray"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
+            }
+
+            @TestMetadata("customNonGenericToArray.kt")
+            public void testCustomNonGenericToArray() throws Exception {
+                runTest("compiler/testData/codegen/bytecodeListing/collectionStubs/toArray/customNonGenericToArray.kt");
+            }
+
+            @TestMetadata("noToArrayInJava.kt")
+            public void testNoToArrayInJava() throws Exception {
+                runTest("compiler/testData/codegen/bytecodeListing/collectionStubs/toArray/noToArrayInJava.kt");
+            }
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/bytecodeListing/coroutines")