New J2K: don't allow open modifier on top-level/private declarations

nj2k/nj2k-services/src/org/jetbrains/kotlin/nj2k/postProcessing/J2kPostProcessor.kt

@@ -177,6 +177,7 @@ private val removeRedundantElementsProcessingGroup =
             RemoveExplicitTypeArgumentsProcessing(),
             RemoveJavaStreamsCollectCallTypeArgumentsProcessing(),
             ExplicitThisInspectionBasedProcessing(),
+            RemoveOpenModifierOnTopLevelDeclarationsProcessing(),
             intentionBasedProcessing(RemoveEmptyClassBodyIntention())
         )
     )

nj2k/nj2k-services/src/org/jetbrains/kotlin/nj2k/postProcessing/processings/inspeсtionLikeProcessings.kt

@@ -504,3 +504,15 @@ class MoveLambdaOutsideParenthesesProcessing :
         element.moveFunctionLiteralOutsideParentheses()
     }
 }
+
+class RemoveOpenModifierOnTopLevelDeclarationsProcessing :
+    InspectionLikeProcessingForElement<KtDeclaration>(KtDeclaration::class.java) {
+    override fun isApplicableTo(element: KtDeclaration, settings: ConverterSettings?): Boolean =
+        element.hasModifier(KtTokens.OPEN_KEYWORD)
+                && (element is KtFunction || element is KtProperty)
+                && element.parent is KtFile
+
+    override fun apply(element: KtDeclaration) {
+        element.removeModifier(KtTokens.OPEN_KEYWORD)
+    }
+}

nj2k/src/org/jetbrains/kotlin/nj2k/conversions/ModalityConversion.kt

@@ -41,6 +41,9 @@ class ModalityConversion(context: NewJ2kConverterContext) : RecursiveApplicableC
         val psi = method.psi<PsiMethod>() ?: return
         val containingClass = method.parentOfType<JKClass>() ?: return
         when {
+            method.visibility == Visibility.PRIVATE -> {
+                method.modality = Modality.FINAL
+            }
             method.modality != Modality.ABSTRACT
                     && psi.findSuperMethods().isNotEmpty() -> {
                 method.modality = Modality.FINAL

nj2k/testData/copyPaste/OpenPublicFunctionToTopLevel.expected.kt

@@ -0,0 +1 @@
+fun x() {}

nj2k/testData/copyPaste/OpenPublicFunctionToTopLevel.java

@@ -0,0 +1,3 @@
+class A {
+    <selection>void x() {}</selection>
+}

nj2k/testData/copyPaste/OpenPublicFunctionToTopLevel.to.kt

@@ -0,0 +1 @@
+<caret>

nj2k/testData/copyPaste/PrivateFunctionToTopLevel.expected.kt

@@ -0,0 +1 @@
+private fun x() {}

nj2k/testData/copyPaste/PrivateFunctionToTopLevel.java

@@ -0,0 +1,3 @@
+class A {
+    <selection>private void x() {}</selection>
+}

nj2k/testData/copyPaste/PrivateFunctionToTopLevel.to.kt

@@ -0,0 +1 @@
+<caret>

nj2k/tests/org/jetbrains/kotlin/nj2k/NewJavaToKotlinCopyPasteConversionTestGenerated.java

@@ -183,6 +183,16 @@ public class NewJavaToKotlinCopyPasteConversionTestGenerated extends AbstractNew
         runTest("nj2k/testData/copyPaste/OnlyQualifier.java");
     }
 
+    @TestMetadata("OpenPublicFunctionToTopLevel.java")
+    public void testOpenPublicFunctionToTopLevel() throws Exception {
+        runTest("nj2k/testData/copyPaste/OpenPublicFunctionToTopLevel.java");
+    }
+
+    @TestMetadata("PrivateFunctionToTopLevel.java")
+    public void testPrivateFunctionToTopLevel() throws Exception {
+        runTest("nj2k/testData/copyPaste/PrivateFunctionToTopLevel.java");
+    }
+
     @TestMetadata("RawTypeRef.java")
     public void testRawTypeRef() throws Exception {
         runTest("nj2k/testData/copyPaste/RawTypeRef.java");