New J2K: Add DefaultNullabilityToNullableConversion

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

@@ -0,0 +1,20 @@
+/*
+ * 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.ast.Nullability
+import org.jetbrains.kotlin.j2k.tree.*
+import org.jetbrains.kotlin.j2k.tree.impl.JKTypeElementImpl
+
+class DefaultNullabilityToNullableConversion : RecursiveApplicableConversionBase() {
+    override fun applyToElement(element: JKTreeElement): JKTreeElement {
+        if (element !is JKTypeElementImpl) return recurse(element)
+        if (element.type.nullability != Nullability.Default) return recurse(element)
+        return recurse(
+            JKTypeElementImpl(element.type.updateNullability(Nullability.Nullable))
+        )
+    }
+}