J2K: singletons are back

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

@@ -31,7 +31,7 @@ class AnnotationConverter(private val converter: Converter) {
     private fun convertAnnotationsOnly(owner: PsiModifierListOwner): Annotations {
         val modifierList = owner.getModifierList()
         val annotations = modifierList?.getAnnotations()?.filter { it.getQualifiedName() !in annotationsToRemove }
-        if (annotations == null || annotations.isEmpty()) return Annotations.Empty()
+        if (annotations == null || annotations.isEmpty()) return Annotations.Empty
 
         val newLines = run {
             if (!modifierList!!.isInSingleLine()) {

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

@@ -68,7 +68,7 @@ class CodeConverter(public val converter: Converter,
             = CodeConverter(converter, expressionConverter, statementConverter, methodReturnType)
 
     public fun convertBlock(block: PsiCodeBlock?, notEmpty: Boolean = true, statementFilter: (PsiStatement) -> Boolean = { true }): Block {
-        if (block == null) return Block.Empty()
+        if (block == null) return Block.Empty
 
         val lBrace = LBrace().assignPrototype(block.getLBrace())
         val rBrace = RBrace().assignPrototype(block.getRBrace())
@@ -103,7 +103,7 @@ class CodeConverter(public val converter: Converter,
     }
 
     public fun convertExpression(expression: PsiExpression?, expectedType: PsiType?): Expression {
-        if (expression == null) return Identifier.Empty()
+        if (expression == null) return Identifier.Empty
 
         var convertedExpression = convertExpression(expression)
         if (expectedType == null || expectedType == PsiType.VOID) return convertedExpression

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

@@ -166,7 +166,7 @@ class ConstructorConverter(private val psiClass: PsiClass,
             val params = converter.convertParameterList(constructor.getParameterList())
             val containingClass = constructor.getContainingClass()
             val typeParameterList = converter.convertTypeParameterList(containingClass?.getTypeParameterList())
-            val factoryFunctionType = ClassType(ReferenceElement(containingClass?.declarationIdentifier() ?: Identifier.Empty(), typeParameterList.parameters).assignNoPrototype(),
+            val factoryFunctionType = ClassType(ReferenceElement(containingClass?.declarationIdentifier() ?: Identifier.Empty, typeParameterList.parameters).assignNoPrototype(),
                                                 Nullability.NotNull,
                                                 converter.settings).assignNoPrototype()
 
@@ -254,7 +254,7 @@ class ConstructorConverter(private val psiClass: PsiClass,
             }
         }
         else {
-            { it -> Block.Empty() }
+            { it -> Block.Empty }
         }
 
         // we need to replace renamed parameter usages in base class constructor arguments and in default values
@@ -359,11 +359,11 @@ class ConstructorConverter(private val psiClass: PsiClass,
             Parameter(property.identifier, property.type, varValModifier, property.annotations, property.modifiers.filter { it in ACCESS_MODIFIERS }).assignPrototypesFrom(property)
         }
 
-        val modifiers = Modifiers.Empty()
+        val modifiers = Modifiers.Empty
         //TODO: we can generate it private when secondary constructors are supported by Kotlin
         //val modifiers = Modifiers(listOf(Modifier.PRIVATE)).assignNoPrototype()
         val parameterList = ParameterList(parameters).assignNoPrototype()
-        val constructorSignature = PrimaryConstructorSignature(Annotations.Empty(), modifiers, parameterList).assignNoPrototype()
+        val constructorSignature = PrimaryConstructorSignature(Annotations.Empty, modifiers, parameterList).assignNoPrototype()
         val updatedMembers = classBody.members.filter { !propertiesToInitialize.contains(it) }
         return ClassBody(constructorSignature, classBody.baseClassParams, updatedMembers, classBody.classObjectMembers, classBody.factoryFunctions, classBody.lBrace, classBody.rBrace)
     }
@@ -395,7 +395,7 @@ class ConstructorConverter(private val psiClass: PsiClass,
                         statements[i] = ReturnStatement(constructorCall).assignNoPrototype()
                         return statements
                     }
-                    val localVar = LocalVariable(tempValIdentifier(), Annotations.Empty(), Modifiers.Empty(), null, constructorCall, true).assignNoPrototype()
+                    val localVar = LocalVariable(tempValIdentifier(), Annotations.Empty, Modifiers.Empty, null, constructorCall, true).assignNoPrototype()
                     statements[i] = DeclarationStatement(listOf(localVar)).assignNoPrototype()
                     statements.add(ReturnStatement(tempValIdentifier()).assignNoPrototype())
                     return statements
@@ -439,8 +439,8 @@ class ConstructorConverter(private val psiClass: PsiClass,
         val initializer = MethodCallExpression.buildNotNull(null, className, arguments).assignNoPrototype()
         if (statements.isNotEmpty()) {
             val localVar = LocalVariable(tempValIdentifier(),
-                                         Annotations.Empty(),
-                                         Modifiers.Empty(),
+                                         Annotations.Empty,
+                                         Modifiers.Empty,
                                          null,
                                          initializer,
                                          true).assignNoPrototype()

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

@@ -236,7 +236,7 @@ class Converter private(private val elementToConvert: PsiElement,
                               annotationConverter.convertAnnotationMethodDefault(method)).assignPrototype(method, noBlankLinesInheritance)
                 }
         val parameterList = ParameterList(parameters).assignNoPrototype()
-        val constructorSignature = PrimaryConstructorSignature(Annotations.Empty(), Modifiers.Empty(), parameterList).assignNoPrototype()
+        val constructorSignature = PrimaryConstructorSignature(Annotations.Empty, Modifiers.Empty, parameterList).assignNoPrototype()
 
         // to convert fields and nested types - they are not allowed in Kotlin but we convert them and let user refactor code
         var classBody = ClassBodyConverter(psiClass, this, false).convertBody()
@@ -246,7 +246,7 @@ class Converter private(private val elementToConvert: PsiElement,
         return Class(psiClass.declarationIdentifier(),
                      convertAnnotations(psiClass) + Annotations(listOf(annotationAnnotation)),
                      convertModifiers(psiClass).without(Modifier.ABSTRACT),
-                     TypeParameterList.Empty(),
+                     TypeParameterList.Empty,
                      listOf(),
                      listOf(),
                      listOf(),
@@ -331,8 +331,8 @@ class Converter private(private val elementToConvert: PsiElement,
         for (parameter in method.getParameterList().getParameters()) {
             if (parameter.hasWriteAccesses(referenceSearcher, method)) {
                 val variable = LocalVariable(parameter.declarationIdentifier(),
-                                             Annotations.Empty(),
-                                             Modifiers.Empty(),
+                                             Annotations.Empty,
+                                             Modifiers.Empty,
                                              null,
                                              parameter.declarationIdentifier(),
                                              false).assignNoPrototype()
@@ -479,7 +479,7 @@ class Converter private(private val elementToConvert: PsiElement,
     public fun convertParameter(parameter: PsiParameter,
                          nullability: Nullability = Nullability.Default,
                          varValModifier: Parameter.VarValModifier = Parameter.VarValModifier.None,
-                         modifiers: Modifiers = Modifiers.Empty(),
+                         modifiers: Modifiers = Modifiers.Empty,
                          defaultValue: DeferredElement<Expression>? = null): Parameter {
         var type = typeConverter.convertVariableType(parameter)
         when (nullability) {
@@ -491,7 +491,7 @@ class Converter private(private val elementToConvert: PsiElement,
     }
 
     public fun convertIdentifier(identifier: PsiIdentifier?): Identifier {
-        if (identifier == null) return Identifier.Empty()
+        if (identifier == null) return Identifier.Empty
 
         return Identifier(identifier.getText()!!).assignPrototype(identifier)
     }
@@ -513,7 +513,7 @@ class Converter private(private val elementToConvert: PsiElement,
         val types = throwsList.getReferencedTypes()
         val refElements = throwsList.getReferenceElements()
         assert(types.size == refElements.size)
-        if (types.isEmpty()) return Annotations.Empty()
+        if (types.isEmpty()) return Annotations.Empty
         val arguments = types.indices.map { index ->
             val convertedType = typeConverter.convertType(types[index], Nullability.NotNull)
             null to deferredElement<Expression> { MethodCallExpression.buildNotNull(null, "javaClass", listOf(), listOf(convertedType)).assignPrototype(refElements[index]) }

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

@@ -398,13 +398,13 @@ class DefaultExpressionConverter : JavaElementVisitor(), ExpressionConverter {
     override fun visitSuperExpression(expression: PsiSuperExpression) {
         val psiQualifier = expression.getQualifier()
         val qualifier = psiQualifier?.getReferenceName()
-        result = SuperExpression(if (qualifier != null) Identifier(qualifier).assignPrototype(psiQualifier) else Identifier.Empty())
+        result = SuperExpression(if (qualifier != null) Identifier(qualifier).assignPrototype(psiQualifier) else Identifier.Empty)
     }
 
     override fun visitThisExpression(expression: PsiThisExpression) {
         val psiQualifier = expression.getQualifier()
         val qualifier = psiQualifier?.getReferenceName()
-        result = ThisExpression(if (qualifier != null) Identifier(qualifier).assignPrototype(psiQualifier) else Identifier.Empty())
+        result = ThisExpression(if (qualifier != null) Identifier(qualifier).assignPrototype(psiQualifier) else Identifier.Empty)
     }
 
     override fun visitTypeCastExpression(expression: PsiTypeCastExpression) {

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

@@ -65,7 +65,7 @@ class DefaultStatementConverter : JavaElementVisitor(), StatementConverter {
 
     override fun visitBreakStatement(statement: PsiBreakStatement) {
         if (statement.getLabelIdentifier() == null) {
-            result = BreakStatement(Identifier.Empty())
+            result = BreakStatement(Identifier.Empty)
         }
         else {
             result = BreakStatement(converter.convertIdentifier(statement.getLabelIdentifier()))
@@ -74,7 +74,7 @@ class DefaultStatementConverter : JavaElementVisitor(), StatementConverter {
 
     override fun visitContinueStatement(statement: PsiContinueStatement) {
         if (statement.getLabelIdentifier() == null) {
-            result = ContinueStatement(Identifier.Empty())
+            result = ContinueStatement(Identifier.Empty)
         }
         else {
             result = ContinueStatement(converter.convertIdentifier(statement.getLabelIdentifier()))
@@ -190,7 +190,7 @@ class DefaultStatementConverter : JavaElementVisitor(), StatementConverter {
                                                    convertedType,
                                                    Parameter.VarValModifier.None,
                                                    annotations,
-                                                   Modifiers.Empty()).assignPrototype(parameter)
+                                                   Modifiers.Empty).assignPrototype(parameter)
                 catches.add(CatchStatement(convertedParameter, blockConverted).assignNoPrototype())
             }
         }

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

@@ -65,7 +65,7 @@ class Annotations(val annotations: List<Annotation>) : Element() {
     fun plus(other: Annotations) = Annotations(annotations + other.annotations).assignNoPrototype()
 
     class object {
-        fun Empty() = Annotations(listOf())
+        val Empty = Annotations(listOf())
     }
 }
 

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

@@ -19,7 +19,7 @@ package org.jetbrains.jet.j2k.ast
 import org.jetbrains.jet.j2k.CodeBuilder
 
 class AnonymousClassBody(body: ClassBody, val extendsTrait: Boolean)
-: Class(Identifier.Empty(), Annotations.Empty(), Modifiers.Empty(), TypeParameterList.Empty(), listOf(), listOf(), listOf(), body) {
+: Class(Identifier.Empty, Annotations.Empty, Modifiers.Empty, TypeParameterList.Empty, listOf(), listOf(), listOf(), body) {
     override fun generateCode(builder: CodeBuilder) {
         body.append(builder)
     }

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

@@ -32,7 +32,7 @@ class Block(val statements: List<Statement>, val lBrace: LBrace, val rBrace: RBr
     }
 
     class object {
-        fun Empty() = Block(listOf(), LBrace(), RBrace())
+        val Empty = Block(listOf(), LBrace(), RBrace())
     }
 }
 

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

@@ -28,7 +28,7 @@ class PrimaryConstructor(annotations: Annotations,
     override fun generateCode(builder: CodeBuilder) { throw IncorrectOperationException() }
 
     public fun initializer(): Initializer
-            = Initializer(body, Modifiers.Empty()).assignPrototypesFrom(this, CommentsAndSpacesInheritance(commentsBefore = false))
+            = Initializer(body, Modifiers.Empty).assignPrototypesFrom(this, CommentsAndSpacesInheritance(commentsBefore = false))
 
     public fun createSignature(converter: Converter): PrimaryConstructorSignature {
         val signature = PrimaryConstructorSignature(annotations, modifiers, parameterList)

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

@@ -57,7 +57,18 @@ fun Element.canonicalCode(): String {
 }
 
 abstract class Element {
-    public open var prototypes: List<PrototypeInfo>? = null
+    public var prototypes: List<PrototypeInfo>? = null
+        set(value) {
+            // do not assign prototypes to singleton instances
+            if (canBeSingleton) {
+                $prototypes = listOf()
+                return
+            }
+            $prototypes = value
+        }
+
+    protected open val canBeSingleton: Boolean
+        get() = isEmpty
 
     public var createdAt: String?
             = if (saveCreationStacktraces)
@@ -75,7 +86,6 @@ abstract class Element {
     object Empty : Element() {
         override fun generateCode(builder: CodeBuilder) { }
         override val isEmpty: Boolean get() = true
-        override var prototypes: List<PrototypeInfo>? by EmptyElementPrototypes // to not hold references to psi
     }
 
     class object {
@@ -83,11 +93,6 @@ abstract class Element {
     }
 }
 
-object EmptyElementPrototypes {
-    public fun get(thisRef: Element, desc: PropertyMetadata): List<PrototypeInfo>? = null
-    public fun set(thisRef: Element, desc: PropertyMetadata, value: List<PrototypeInfo>?) { }
-}
-
 // this class should never be created directly - Converter.deferredElement() should be used!
 class DeferredElement<TResult : Element>(
         private var generator: (CodeConverter) -> TResult,
@@ -100,6 +105,10 @@ class DeferredElement<TResult : Element>(
         assignNoPrototype()
     }
 
+    // need to override it to not use isEmpty
+    override val canBeSingleton: Boolean
+        get() = false
+
     public fun unfold(codeConverter: CodeConverter) {
         assert(result == null)
         result = generator(codeConverter)

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

@@ -25,6 +25,5 @@ abstract class Expression() : Statement() {
     object Empty : Expression() {
         override fun generateCode(builder: CodeBuilder) {}
         override val isEmpty: Boolean get() = true
-        override var prototypes: List<PrototypeInfo>? by EmptyElementPrototypes // to not hold references to psi
     }
 }

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

@@ -22,7 +22,7 @@ import org.jetbrains.jet.j2k.CodeConverter
 
 fun PsiNameIdentifierOwner.declarationIdentifier(): Identifier {
     val name = getName()
-    return if (name != null) Identifier(name, false).assignPrototype(getNameIdentifier()!!) else Identifier.Empty()
+    return if (name != null) Identifier(name, false).assignPrototype(getNameIdentifier()!!) else Identifier.Empty
 }
 
 class Identifier(
@@ -51,7 +51,7 @@ class Identifier(
     override fun toString() = if (isNullable) "$name?" else name
 
     class object {
-        fun Empty() = Identifier("")
+        val Empty = Identifier("")
 
         val ONLY_KOTLIN_KEYWORDS: Set<String> = setOf(
                 "package", "as", "type", "val", "var", "fun", "is", "in", "object", "when", "trait", "This"

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

@@ -18,11 +18,15 @@ package org.jetbrains.jet.j2k.ast
 
 import org.jetbrains.jet.j2k.*
 
-class Initializer(val body: DeferredElement<Block>, modifiers: Modifiers) : Member(Annotations.Empty(), modifiers) {
+class Initializer(val body: DeferredElement<Block>, modifiers: Modifiers) : Member(Annotations.Empty, modifiers) {
     override fun generateCode(builder: CodeBuilder) {
         builder.append(body)
     }
 
     override val isEmpty: Boolean
         get() = body.isEmpty
+
+    // need to override it to not use isEmpty
+    override val canBeSingleton: Boolean
+        get() = false
 }

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

@@ -60,7 +60,7 @@ class Modifiers(val modifiers: Collection<Modifier>) : Element() {
     fun accessModifier(): Modifier? = modifiers.firstOrNull { it in ACCESS_MODIFIERS }
 
     class object {
-        fun Empty() = Modifiers(listOf())
+        val Empty = Modifiers(listOf())
     }
 }
 

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

@@ -23,7 +23,6 @@ abstract class Statement() : Element() {
     object Empty : Statement() {
         override fun generateCode(builder: CodeBuilder) { }
         override val isEmpty: Boolean get() = true
-        override var prototypes: List<PrototypeInfo>? by EmptyElementPrototypes // to not hold references to psi
     }
 }
 
@@ -106,13 +105,13 @@ class ForeachStatement(
     }
 }
 
-class BreakStatement(val label: Identifier = Identifier.Empty()) : Statement() {
+class BreakStatement(val label: Identifier = Identifier.Empty) : Statement() {
     override fun generateCode(builder: CodeBuilder) {
         builder.append("break").appendWithPrefix(label, "@")
     }
 }
 
-class ContinueStatement(val label: Identifier = Identifier.Empty()) : Statement() {
+class ContinueStatement(val label: Identifier = Identifier.Empty) : Statement() {
     override fun generateCode(builder: CodeBuilder) {
         builder.append("continue").appendWithPrefix(label, "@")
     }

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

@@ -56,7 +56,7 @@ class TypeParameterList(val parameters: List<TypeParameter>) : Element() {
     private fun hasWhere(): Boolean = parameters.any { it.hasWhere() }
 
     class object {
-        fun Empty() = TypeParameterList(listOf())
+        val Empty = TypeParameterList(listOf())
     }
 }
 
@@ -69,5 +69,5 @@ fun Converter.convertTypeParameterList(typeParameterList: PsiTypeParameterList?)
     return if (typeParameterList != null)
         TypeParameterList(typeParameterList.getTypeParameters()!!.toList().map { convertTypeParameter(it) }).assignPrototype(typeParameterList)
     else
-        TypeParameterList.Empty()
+        TypeParameterList.Empty
 }

j2k/src/org/jetbrains/jet/j2k/usageProcessing/FieldToPropertyProcessing.kt

@@ -39,7 +39,7 @@ class FieldToPropertyProcessing(val field: PsiField, val propertyName: String, v
                     if (refExpr.resolve() == null)
                         identifier
                     else
-                        QualifiedExpression(ThisExpression(Identifier.Empty()).assignNoPrototype(), identifier) //TODO: this is not correct in case of nested/anonymous classes
+                        QualifiedExpression(ThisExpression(Identifier.Empty).assignNoPrototype(), identifier) //TODO: this is not correct in case of nested/anonymous classes
                 }
             }
         }