Java to Kotlin converter: more smartness about nullability

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

@@ -218,7 +218,7 @@ public class Converter(val project: Project, val settings: ConverterSettings) {
                      typeConverter.convertVariableType(field),
                      convertExpression(field.getInitializer(), field.getType()),
                      field.hasModifierProperty(PsiModifier.FINAL),
-                     field.countWriteAccesses(field.getContainingClass()))
+                     field.hasWriteAccesses(field.getContainingClass()))
     }
 
     private fun convertMethod(method: PsiMethod, membersToRemove: MutableSet<PsiMember>): Function {

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

@@ -44,7 +44,7 @@ class TypeConverter(val settings: ConverterSettings) {
             val initializer = variable.getInitializer()
             if (initializer != null) {
                 val initializerNullability = initializer.nullability()
-                if (variable.hasModifierProperty(PsiModifier.FINAL)) { //TODO: replace check for final modifier with effective final
+                if (variable.isEffectivelyFinal()) {
                     nullability = initializerNullability
                 }
                 else if (initializerNullability == Nullability.Nullable) { // if variable is not final then non-nullability of initializer does not mean that variable is non-null
@@ -159,6 +159,19 @@ class TypeConverter(val settings: ConverterSettings) {
                 return otherOperand is PsiLiteralExpression && otherOperand.getType() == PsiType.NULL
             }
         }
+        else if (parent is PsiVariable && usage == parent.getInitializer() && parent.isEffectivelyFinal()) {
+            return convertVariableType(parent).isNullable
+        }
         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
+            is PsiParameter -> true
+            else -> false
+        }
+    }
 }

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

@@ -46,6 +46,9 @@ fun findMethodCalls(method: PsiMethod, scope: PsiElement): Collection<PsiMethodC
 fun PsiVariable.countWriteAccesses(scope: PsiElement?): Int
         = if (scope != null) findVariableUsages(this, scope).count { PsiUtil.isAccessedForWriting(it) } else 0
 
+fun PsiVariable.hasWriteAccesses(scope: PsiElement?): Boolean
+        = if (scope != null) findVariableUsages(this, scope).any { PsiUtil.isAccessedForWriting(it) } else false
+
 fun PsiModifierListOwner.nullabilityFromAnnotations(): Nullability {
     val annotations = getModifierList()?.getAnnotations() ?: return Nullability.Default
     return if (annotations.any { NOT_NULL_ANNOTATIONS.contains(it.getQualifiedName()) })

j2k/src/org/jetbrains/jet/j2k/ast/EnumConstant.kt

@@ -22,7 +22,7 @@ class EnumConstant(
         modifiers: Set<Modifier>,
         `type`: Type,
         params: Element
-) : Field(identifier, members, modifiers, `type`.toNotNullType(), params, true, 0) {
+) : Field(identifier, members, modifiers, `type`.toNotNullType(), params, true, false) {
 
     override fun toKotlin(): String {
         if (initializer.toKotlin().isEmpty()) {

j2k/src/org/jetbrains/jet/j2k/ast/Field.kt

@@ -26,13 +26,13 @@ open class Field(
         val `type`: Type,
         val initializer: Element,
         val isVal: Boolean,
-        val writingAccesses: Int
+        private val hasWriteAccesses: Boolean
 ) : Member(comments, modifiers) {
 
     override fun toKotlin(): String {
         val declaration = commentsToKotlin() + modifiersToKotlin() + (if (isVal) "val " else "var ") + identifier.toKotlin() + " : " + `type`.toKotlin()
         return if (initializer.isEmpty)
-            declaration + (if (isVal && !isStatic() && writingAccesses != 0) "" else " = " + getDefaultInitializer(this))
+            declaration + (if (isVal && !isStatic() && hasWriteAccesses) "" else " = " + getDefaultInitializer(this))
         else
             declaration + " = " + initializer.toKotlin()
     }

j2k/src/org/jetbrains/jet/j2k/visitors/StatementVisitor.kt

@@ -21,6 +21,7 @@ import org.jetbrains.jet.j2k.Converter
 import org.jetbrains.jet.j2k.ast.*
 import org.jetbrains.jet.j2k.countWriteAccesses
 import java.util.ArrayList
+import org.jetbrains.jet.j2k.hasWriteAccesses
 
 class StatementVisitor(public val converter: Converter) : JavaElementVisitor() {
     public var result: Statement = Statement.Empty
@@ -82,8 +83,8 @@ class StatementVisitor(public val converter: Converter) : JavaElementVisitor() {
 
         val loopVar = initialization?.getFirstChild() as? PsiLocalVariable
         val onceWritableIterator = loopVar != null
-                && loopVar.countWriteAccesses(body) == 0
+                && !loopVar.hasWriteAccesses(body)
-                && loopVar.countWriteAccesses(condition) == 0
+                && !loopVar.hasWriteAccesses(condition)
                 && loopVar.countWriteAccesses(update) == 1
 
         val operationTokenType = (condition as? PsiBinaryExpression)?.getOperationTokenType()

j2k/tests/test/org/jetbrains/jet/j2k/test/JavaToKotlinConverterTestGenerated.java

@@ -1926,6 +1926,26 @@ public class JavaToKotlinConverterTestGenerated extends AbstractJavaToKotlinConv
             doTest("j2k/tests/testData/ast/nullability/MethodResultComparedWithNull.java");
         }
         
+        @TestMetadata("MethodResultComparedWithNull2.java")
+        public void testMethodResultComparedWithNull2() throws Exception {
+            doTest("j2k/tests/testData/ast/nullability/MethodResultComparedWithNull2.java");
+        }
+        
+        @TestMetadata("MethodResultComparedWithNull3.java")
+        public void testMethodResultComparedWithNull3() throws Exception {
+            doTest("j2k/tests/testData/ast/nullability/MethodResultComparedWithNull3.java");
+        }
+        
+        @TestMetadata("MethodResultComparedWithNull4.java")
+        public void testMethodResultComparedWithNull4() throws Exception {
+            doTest("j2k/tests/testData/ast/nullability/MethodResultComparedWithNull4.java");
+        }
+        
+        @TestMetadata("MethodResultInitializesNullableField.java")
+        public void testMethodResultInitializesNullableField() throws Exception {
+            doTest("j2k/tests/testData/ast/nullability/MethodResultInitializesNullableField.java");
+        }
+        
         @TestMetadata("MethodReturnsNull.java")
         public void testMethodReturnsNull() throws Exception {
             doTest("j2k/tests/testData/ast/nullability/MethodReturnsNull.java");

j2k/tests/testData/ast/callChainExpression/libraryMethodCallFromInstance-settings.kt

@@ -11,7 +11,7 @@ class Library() {
 
 class User() {
     fun main() {
-        val lib: Library? = Library()
+        val lib: Library = Library()
         lib?.call()
         lib?.getString()?.isEmpty()
 

j2k/tests/testData/ast/nullability/FieldComparedWithNull.java

@@ -1,6 +1,6 @@
 //file
 class C {
-    private String s = "";
+    private String s = x();
 
     void foo() {
         if (s == null) {

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

@@ -1,5 +1,5 @@
 class C() {
-    private var s: String? = ""
+    private var s: String? = x()
 
     fun foo() {
         if (s == null) {

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull2.java

@@ -0,0 +1,13 @@
+//file
+interface I {
+    String getString();
+}
+
+class C {
+    void foo(I i) {
+        final String result = i.getString();
+        if (result != null) {
+            print(result);
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull2.kt

@@ -0,0 +1,12 @@
+trait I {
+    public fun getString(): String?
+}
+
+class C() {
+    fun foo(i: I) {
+        val result = i.getString()
+        if (result != null) {
+            print(result)
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull3.java

@@ -0,0 +1,13 @@
+//file
+interface I {
+    String getString();
+}
+
+class C {
+    void foo(I i) {
+        String result = i.getString();
+        if (result != null) {
+            print(result);
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull3.kt

@@ -0,0 +1,12 @@
+trait I {
+    public fun getString(): String?
+}
+
+class C() {
+    fun foo(i: I) {
+        val result = i.getString()
+        if (result != null) {
+            print(result)
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull4.java

@@ -0,0 +1,14 @@
+//file
+interface I {
+    String getString();
+}
+
+class C {
+    void foo(I i, boolean b) {
+        String result = i.getString();
+        if (b) result = null;
+        if (result != null) {
+            print(result);
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull4.kt

@@ -0,0 +1,14 @@
+trait I {
+    public fun getString(): String
+}
+
+class C() {
+    fun foo(i: I, b: Boolean) {
+        val result = i.getString()
+        if (b)
+            result = null
+        if (result != null) {
+            print(result)
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultInitializesNullableField.java

@@ -0,0 +1,8 @@
+//file
+import org.jetbrains.annotations.Nullable;
+
+class C {
+    @Nullable private final String string = getString();
+
+    static String getString() { return x(); }
+}

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

@@ -0,0 +1,10 @@
+class C() {
+    private val string: String? = getString()
+
+    class object {
+
+        fun getString(): String? {
+            return x()
+        }
+    }
+}