New J2K: Add body stub for abstract methods & set return type to void for <init>

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

@@ -248,10 +248,14 @@ class JavaToJKTreeBuilder(var symbolProvider: JKSymbolProvider) {
         fun PsiMethod.toJK(): JKJavaMethod {
             return JKJavaMethodImpl(
                 with(modifierMapper) { modifierList.toJK() },
-                with(expressionTreeMapper) { returnTypeElement?.toJK() ?: TODO() },
+                with(expressionTreeMapper) {
+                    returnTypeElement?.toJK()
+                            ?: JKTypeElementImpl(JKJavaVoidType).takeIf { isConstructor }
+                            ?: TODO()
+                },
                 JKNameIdentifierImpl(name),
                 parameterList.parameters.map { it -> it.toJK() },
-                body?.toJK() ?: TODO()
+                body?.toJK() ?: JKBodyStub
             ).also {
                 (symbolProvider.provideSymbol(this) as? JKUniverseMethodSymbol)?.run { target = it }
             }

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

@@ -173,4 +173,23 @@ class JKAssertStatementImpl(condition: JKExpression, description: JKExpression)
     override val condition by child(condition)
 
     override fun <R, D> accept(visitor: JKVisitor<R, D>, data: D): R = visitor.visitAssertStatement(this, data)
+}
+
+object JKBodyStub : JKBlock, JKTreeElement {
+    override var statements: List<JKStatement>
+        get() = emptyList()
+        set(value) {}
+
+    override fun <R, D> accept(visitor: JKVisitor<R, D>, data: D): R = visitor.visitBlock(this, data)
+
+    override fun <D> acceptChildren(visitor: JKVisitor<Unit, D>, data: D) {}
+
+    override val parent: JKElement?
+        get() = null
+
+    override fun detach(from: JKElement) {
+    }
+
+    override fun attach(to: JKElement) {
+    }
 }