Java to Kotlin converter: added heuristics that values of types like Integer are likely nullable

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

@@ -72,7 +72,8 @@ class TypeConverter(val settings: ConverterSettings, val conversionScope: Conver
 
     private fun variableNullabilityNoCache(variable: PsiVariable): Nullability {
         if (variable is PsiEnumConstant) return Nullability.NotNull
-        if (variable.getType() is PsiPrimitiveType) return Nullability.NotNull
+        val variableType = variable.getType()
+        if (variableType is PsiPrimitiveType) return Nullability.NotNull
 
         var nullability = variable.nullabilityFromAnnotations()
 
@@ -102,6 +103,11 @@ class TypeConverter(val settings: ConverterSettings, val conversionScope: Conver
             }
         }
 
+        // variables of types like Integer are most likely nullable
+        if (nullability == Nullability.Default && variableType.getCanonicalText() in boxingTypes) {
+            return Nullability.Nullable
+        }
+
         if (!conversionScope.contains(variable)) { // do not analyze usages out of our conversion scope
             if (variable is PsiParameter) {
                 // Object.equals corresponds to Any.equals which has nullable parameter:
@@ -158,7 +164,8 @@ class TypeConverter(val settings: ConverterSettings, val conversionScope: Conver
     }
 
     private fun methodNullabilityNoCache(method: PsiMethod): Nullability {
-        if (method.getReturnType() is PsiPrimitiveType) return Nullability.NotNull
+        val returnType = method.getReturnType()
+        if (returnType is PsiPrimitiveType) return Nullability.NotNull
 
         var nullability = method.nullabilityFromAnnotations()
 
@@ -167,6 +174,11 @@ class TypeConverter(val settings: ConverterSettings, val conversionScope: Conver
             nullability = superSignatures.map { methodNullability(it.getMethod()) }.firstOrNull { it != Nullability.Default } ?: Nullability.Default
         }
 
+        // methods of types like Integer are most likely nullable
+        if (nullability == Nullability.Default && returnType?.getCanonicalText() in boxingTypes) {
+            return Nullability.Nullable
+        }
+
         if (!conversionScope.contains(method)) return nullability // do not analyze body and usages of methods out of our conversion scope
 
         if (nullability == Nullability.Default) {
@@ -265,4 +277,17 @@ class TypeConverter(val settings: ConverterSettings, val conversionScope: Conver
         else
             Nullability.Default
     }
+
+    class object {
+        private val boxingTypes: Set<String> = setOf(
+                CommonClassNames.JAVA_LANG_BYTE,
+                CommonClassNames.JAVA_LANG_CHARACTER,
+                CommonClassNames.JAVA_LANG_DOUBLE,
+                CommonClassNames.JAVA_LANG_FLOAT,
+                CommonClassNames.JAVA_LANG_INTEGER,
+                CommonClassNames.JAVA_LANG_LONG,
+                CommonClassNames.JAVA_LANG_SHORT,
+                CommonClassNames.JAVA_LANG_BOOLEAN
+        )
+    }
 }

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

@@ -1,5 +1,5 @@
 class A() {
-    private var i = getByte().toInt()
+    private var i: Int? = getByte().toInt()
 
     fun foo() {
         i = 10

j2k/tests/testData/ast/formatting/nonStaticMembers.kt

@@ -5,7 +5,7 @@ class F() {
 
     fun f2() {
     }
-    var i = 0
+    var i: Int? = 0
 
     fun f3() {
     }

j2k/tests/testData/ast/formatting/nonStaticMembersWithComments.kt

@@ -16,7 +16,7 @@ class F() {
 
     fun f2() {
     }
-    var i = 0
+    var i: Int? = 0
 
     fun f3() {
     }

j2k/tests/testData/ast/formatting/staticAndNonStaticMembersWithComments.kt

@@ -24,7 +24,7 @@ class F() {
 
         fun f1() {
         }
-        var i = 0
+        var i: Int? = 0
 
         //c5
 

j2k/tests/testData/ast/formatting/staticMembersWithComments.kt

@@ -17,7 +17,7 @@ class F() {
 
         fun f2() {
         }
-        var i = 0
+        var i: Int? = 0
 
         fun f3() {
         }

j2k/tests/testData/ast/issues/kt-543-boxed.kt

@@ -1,7 +1,7 @@
 package demo
 
 class Test() {
-    fun putInt(i: Int) {
+    fun putInt(i: Int?) {
     }
 
     fun test() {

j2k/tests/testData/ast/issues/kt-543-mixed.kt

@@ -1,7 +1,7 @@
 package demo
 
 class Test() {
-    fun putInt(i: Int) {
+    fun putInt(i: Int?) {
     }
 
     fun test() {

j2k/tests/testData/ast/issues/kt-792-mixed.kt

@@ -1,6 +1,6 @@
 package demo
 
-class Test(i: Int) {
+class Test(i: Int?) {
 
     fun test() {
         val i = 10

j2k/tests/testData/ast/issues/kt-794-mixed.kt

@@ -1,11 +1,11 @@
 package demo
 
 class Test() {
-    fun getInteger(i: Int): Int {
+    fun getInteger(i: Int?): Int? {
         return i
     }
 
     fun test() {
-        val i = getInteger(10)
+        val i = getInteger(10)!!
     }
 }

j2k/tests/testData/ast/localVariable/autoBangBang.kt

@@ -1,4 +1,4 @@
-fun foo(i: Int) {
+fun foo(i: Int?) {
-    var i1 = i
+    var i1 = i!!
     i1++
 }

j2k/tests/testData/ast/localVariable/conversion.kt

@@ -1,4 +1,4 @@
 fun foo(b: Byte) {
-    var i = b.toInt()
+    var i: Int? = b.toInt()
     if (p) i = 10
 }