New J2K: Add conversion that moves statics to companion object

j2k/newSrc/org/jetbrains/kotlin/j2k/ConversionsRunner.kt

@@ -37,6 +37,7 @@ object ConversionsRunner {
         LiteralConversion(),
         InnerClassConversion(),
         ModifiersConversion(context),
+        StaticsToCompanionExtractConversion(),
         PolyadicExpressionConversion(),
         BinaryExpressionConversion()
     )

j2k/newSrc/org/jetbrains/kotlin/j2k/NewCodeBuilder.kt

@@ -37,6 +37,8 @@ class NewCodeBuilder {
         JKClass.ClassKind.CLASS -> "class"
         JKClass.ClassKind.ENUM -> "enum class"
         JKClass.ClassKind.INTERFACE -> "interface"
+        JKClass.ClassKind.OBJECT -> "object"
+        JKClass.ClassKind.COMPANION -> "companion object"
     }
 
     inner class Visitor : JKVisitorVoid {

j2k/newSrc/org/jetbrains/kotlin/j2k/conversions/StaticsToCompanionExtractConversion.kt

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2010-2018 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 org.jetbrains.kotlin.j2k.conversions
+
+import org.jetbrains.kotlin.j2k.tree.*
+import org.jetbrains.kotlin.j2k.tree.impl.*
+
+class StaticsToCompanionExtractConversion : RecursiveApplicableConversionBase() {
+    override fun applyToElement(element: JKTreeElement): JKTreeElement {
+        if (element !is JKClass) return recurse(element)
+        if (element.classKind == JKClass.ClassKind.COMPANION || element.classKind == JKClass.ClassKind.OBJECT) return element
+        val statics = element.declarationList.filter { declaration ->
+            declaration is JKModifierListOwner &&
+                    declaration.modifierList.modifiers.any { it is JKJavaModifier && it.type == JKJavaModifier.JavaModifierType.STATIC }
+        }
+
+        if (statics.isEmpty()) return recurse(element)
+        val companion = findOrCreateCompanion(element)
+
+
+        element.declarationList -= statics
+        companion.declarationList += statics.onEach { declaration ->
+            (declaration as JKModifierListOwner)
+            declaration.modifierList.modifiers =
+                    declaration.modifierList.modifiers.filterNot { it is JKJavaModifier && it.type == JKJavaModifier.JavaModifierType.STATIC }
+        }
+
+        return recurse(element)
+    }
+
+    fun findOrCreateCompanion(element: JKClass): JKClass {
+        val companion = element.declarationList
+            .asSequence()
+            .filterIsInstance<JKClass>()
+            .firstOrNull { it.classKind == JKClass.ClassKind.COMPANION }
+
+        if (companion != null) return companion
+
+        return JKClassImpl(
+            JKModifierListImpl(
+                listOf(
+                    JKAccessModifierImpl(JKAccessModifier.Visibility.PUBLIC),
+                    JKModalityModifierImpl(JKModalityModifier.Modality.FINAL)
+                )
+            ),
+            JKNameIdentifierImpl(""),
+            JKInheritanceInfoImpl(emptyList()),
+            JKClass.ClassKind.COMPANION
+        ).also { element.declarationList += it }
+    }
+}

j2k/newSrc/org/jetbrains/kotlin/j2k/tree/jk.kt

@@ -47,7 +47,7 @@ interface JKClass : JKDeclaration, JKModifierListOwner {
     var classKind: ClassKind
 
     enum class ClassKind {
-        ABSTRACT, ANNOTATION, CLASS, ENUM, INTERFACE
+        ABSTRACT, ANNOTATION, CLASS, ENUM, INTERFACE, OBJECT, COMPANION
     }
 }