Java to Kotlin converter: more cases when field can be declared as val

j2k/src/org/jetbrains/jet/j2k/Converter.kt

@@ -285,7 +285,7 @@ public class Converter private(val project: Project, val settings: ConverterSett
         else {
             val initializer = field.getInitializer()
             val convertedType = typeConverter.convertVariableType(field)
-            val isVal = field.isEffectivelyFinal()
+            val isVal = isVal(field)
             val omitType = !settings.specifyFieldTypeByDefault &&
                     initializer != null &&
                     (modifiers.isPrivate && (isVal || convertedType == typeConverter.convertExpressionType(initializer)) ||
@@ -302,6 +302,29 @@ public class Converter private(val project: Project, val settings: ConverterSett
         return converted.assignPrototype(field)
     }
 
+    private fun isVal(field: PsiField): Boolean {
+        if (field.hasModifierProperty(PsiModifier.FINAL)) return true
+        if (!field.hasModifierProperty(PsiModifier.PRIVATE)) return false
+        val containingClass = field.getContainingClass() ?: return false
+        val writes = findVariableUsages(field, containingClass).filter { PsiUtil.isAccessedForWriting(it) }
+        if (writes.size == 0) return true
+        if (writes.size > 1) return false
+        val write = writes.single()
+        val parent = write.getParent()
+        if (parent is PsiAssignmentExpression &&
+                parent.getOperationSign().getTokenType() == JavaTokenType.EQ &&
+                isQualifierEmptyOrThis(write)) {
+            val constructor = write.getContainingConstructor()
+            if (constructor != null &&
+                    constructor.getContainingClass() == containingClass &&
+                    parent.getParent() is PsiExpressionStatement &&
+                    parent.getParent()?.getParent() == constructor.getBody()) {
+                return true
+            }
+        }
+        return false
+    }
+
     private fun convertMethod(method: PsiMethod, membersToRemove: MutableSet<PsiMember>): Function {
         return withMethodReturnType(method.getReturnType()).doConvertMethod(method, membersToRemove).assignPrototype(method)
     }
@@ -428,7 +451,7 @@ public class Converter private(val project: Project, val settings: ConverterSett
                 val (field, `type`) = parameterToField[parameter]!!
                 Parameter(field.declarationIdentifier(),
                           `type`,
-                          if (field.hasModifierProperty(PsiModifier.FINAL)) Parameter.VarValModifier.Val else Parameter.VarValModifier.Var,
+                          if (isVal(field)) Parameter.VarValModifier.Val else Parameter.VarValModifier.Var,
                           convertAnnotations(parameter) + convertAnnotations(field),
                           convertModifiers(field).filter { it in ACCESS_MODIFIERS }).assignPrototypes(listOf(parameter, field), inheritBlankLinesBefore = false)
             }

j2k/src/org/jetbrains/jet/j2k/TypeConverter.kt

@@ -263,4 +263,13 @@ class TypeConverter(val settings: ConverterSettings, val conversionScope: Conver
         }
         return false
     }
+
+    private fun PsiVariable.isEffectivelyFinal(): Boolean {
+        if (hasModifierProperty(PsiModifier.FINAL)) return true
+        return when(this) {
+            is PsiLocalVariable -> !hasWriteAccesses(getContainingMethod())
+            is PsiField -> if (hasModifierProperty(PsiModifier.PRIVATE)) !hasWriteAccesses(getContainingClass()) else false
+            else -> false
+        }
+    }
 }

j2k/src/org/jetbrains/jet/j2k/Utils.kt

@@ -93,12 +93,3 @@ fun PsiElement.isInSingleLine(): Boolean {
     }
     return true
 }
-
-fun PsiVariable.isEffectivelyFinal(): Boolean {
-    if (hasModifierProperty(PsiModifier.FINAL)) return true
-    return when(this) {
-        is PsiLocalVariable -> !hasWriteAccesses(getContainingMethod())
-        is PsiField -> if (hasModifierProperty(PsiModifier.PRIVATE)) !hasWriteAccesses(getContainingClass()) else false
-        else -> false
-    }
-}

j2k/tests/testData/ast/constructors/genericIdentifier.kt

@@ -1,4 +1,4 @@
-public class Identifier<T> private(private val myName: T, private var myHasDollar: Boolean) {
+public class Identifier<T> private(private val myName: T, private val myHasDollar: Boolean) {
     private var myNullable = true
 
     public fun getName(): T {

j2k/tests/testData/ast/constructors/identifier.kt

@@ -1,4 +1,4 @@
-public class Identifier private(private val myName: String, private var myHasDollar: Boolean) {
+public class Identifier private(private val myName: String, private val myHasDollar: Boolean) {
     private var myNullable = true
 
     public fun getName(): String {

j2k/tests/testData/ast/enum/fieldsWithPrimaryPrivateConstructor.kt

@@ -1,4 +1,4 @@
-enum class Color private(private var code: Int) {
+enum class Color private(private val code: Int) {
     WHITE : Color(21)
     BLACK : Color(22)
     RED : Color(23)

j2k/tests/testData/ast/enum/primaryPrivateConstructor.kt

@@ -1,6 +1,6 @@
 package demo
 
-enum class Color private(private var code: Int) {
+enum class Color private(private val code: Int) {
 
     public fun getCode(): Int {
         return code

j2k/tests/testData/ast/field/valOrVar.java

@@ -5,6 +5,23 @@ class A {
     private int field3 = 0;
     final int field4 = 0;
     int field5 = 0;
+    private int field6;
+    private int field7;
+    private int field8;
+    private int field9;
+    private int field10;
+    private int field11;
+
+    A(int p1, int p2, A a) {
+        field6 = p1;
+        field7 = 10;
+        this.field8 = p2;
+        this.field9 = 10;
+        if (p1 > 0) {
+            this.field10 = 10;
+        }
+        a.field11 = 10;
+    }
 
     void foo() {
         field3 = field2;

j2k/tests/testData/ast/field/valOrVar.kt

@@ -1,11 +1,24 @@
-class A() {
+class A(private val field6: Int, private val field8: Int, a: A) {
     private val field1 = 0
     private val field2 = 0
     private var field3 = 0
     val field4 = 0
     var field5 = 0
+    private val field7: Int
+    private val field9: Int
+    private var field10: Int = 0
+    private var field11: Int = 0
 
     fun foo() {
         field3 = field2
     }
+
+    {
+        field7 = 10
+        this.field9 = 10
+        if (field6 > 0) {
+            this.field10 = 10
+        }
+        a.field11 = 10
+    }
 }

j2k/tests/testData/ast/inheritance/classOneExtendsBaseGeneric.kt

@@ -1,3 +1,3 @@
 class Base<T>(name: T)
 
-class One<T, K>(name: T, private var mySecond: K) : Base<T>(name)
+class One<T, K>(name: T, private val mySecond: K) : Base<T>(name)

j2k/tests/testData/ast/inheritance/classOneExtendsBaseWithZeroParamsNonEmptyConstructor.kt

@@ -1,3 +1,3 @@
 class Base(name: String)
 
-class One(name: String, private var mySecond: String) : Base(name)
+class One(name: String, private val mySecond: String) : Base(name)

j2k/tests/testData/ast/issues/kt-638.kt

@@ -1,4 +1,4 @@
-public class Identifier<T> private(private val myName: T, private var myHasDollar: Boolean) {
+public class Identifier<T> private(private val myName: T, private val myHasDollar: Boolean) {
     private var myNullable = true
 
     public fun getName(): T {

j2k/tests/testData/ast/nullability/FieldComparedWithNull2.kt

@@ -1,4 +1,4 @@
-class C(private var s: String?) {
+class C(private val s: String?) {
 
     fun foo() {
         if (s != null) {

j2k/tests/testData/ast/nullability/FieldComparedWithNull4.kt

@@ -1,4 +1,4 @@
-class C(private var s: String?) {
+class C(private val s: String?) {
     {
         if (s == null) {
             System.out.print("null")