Java to Kotlin converter: no intermediate __ variable in factory function if body is simple

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

@@ -254,16 +254,23 @@ public class Converter private(val project: Project, val settings: ConverterSett
                 }
             }
 
-            val initializer = MethodCallExpression.buildNotNull(null, className.name, finalOrWithEmptyInitializerFields.map { initializers[it]!! })
-            initializer.assignNoPrototype()
-            val localVar = LocalVariable(FactoryFunction.tempValIdentifier(),
-                                         Annotations.Empty,
-                                         Modifiers.Empty,
-                                         null,
-                                         initializer,
-                                         true).assignNoPrototype()
-            statements.add(0, DeclarationStatement(listOf(localVar)).assignNoPrototype())
-            statements.add(ReturnStatement(FactoryFunction.tempValIdentifier()).assignNoPrototype())
+            val initializer = MethodCallExpression.buildNotNull(null,
+                                                                className.name,
+                                                                finalOrWithEmptyInitializerFields.map { initializers[it]!! }).assignNoPrototype()
+            if (statements.isNotEmpty()) {
+                val localVar = LocalVariable(FactoryFunction.tempValIdentifier(),
+                                             Annotations.Empty,
+                                             Modifiers.Empty,
+                                             null,
+                                             initializer,
+                                             true).assignNoPrototype()
+                statements.add(0, DeclarationStatement(listOf(localVar)).assignNoPrototype())
+                statements.add(ReturnStatement(FactoryFunction.tempValIdentifier()).assignNoPrototype())
+            }
+            else {
+                statements.add(ReturnStatement(initializer).assignNoPrototype())
+            }
+
             factoryFunction.body = Block(statements, LBrace().assignNoPrototype(), RBrace().assignNoPrototype()).assignNoPrototype()
         }
 
@@ -282,27 +289,36 @@ public class Converter private(val project: Project, val settings: ConverterSett
     private fun correctFactoryFunctions(classBody: ClassBody, className: String) {
         for (factoryFunction in classBody.factoryFunctions()) {
             val body = factoryFunction.body!!
-            val statements = ArrayList(body.statements)
-
-            // searching for other constructor call in form "this(...)"
-            // it's not necessary the first statement because of statements inserted for writable parameters
-            for (i in statements.indices) {
-                val statement = statements[i]
-                if (statement is MethodCallExpression) {
-                    if ((statement.methodExpression as? Identifier)?.name == "this") {
-                        val constructorCall = MethodCallExpression.buildNotNull(null, className, statement.arguments).assignPrototypesFrom(statement)
-                        val localVar = LocalVariable(FactoryFunction.tempValIdentifier(), Annotations.Empty, Modifiers.Empty, null, constructorCall, true).assignNoPrototype()
-                        statements[i] = DeclarationStatement(listOf(localVar)).assignNoPrototype()
-                        break
-                    }
-                }
-            }
-
-            statements.add(ReturnStatement(FactoryFunction.tempValIdentifier()).assignNoPrototype())
+            val statements = correctFactoryFunctionStatements(body, className)
             factoryFunction.body = Block(statements, body.lBrace, body.rBrace).assignPrototypesFrom(body)
         }
     }
 
+    private fun correctFactoryFunctionStatements(body: Block, className: String): List<Statement> {
+        val statements = ArrayList(body.statements)
+
+        // searching for other constructor call in form "this(...)"
+        // it's not necessary the first statement because of statements inserted for writable parameters
+        for (i in statements.indices) {
+            val statement = statements[i]
+            if (statement is MethodCallExpression) {
+                if ((statement.methodExpression as? Identifier)?.name == "this") {
+                    val constructorCall = MethodCallExpression.buildNotNull(null, className, statement.arguments).assignPrototypesFrom(statement)
+                    if (i == statements.lastIndex) { // constructor call is the last statement - no intermediate variable needed
+                        statements[i] = ReturnStatement(constructorCall).assignNoPrototype()
+                        return statements
+                    }
+                    val localVar = LocalVariable(FactoryFunction.tempValIdentifier(), Annotations.Empty, Modifiers.Empty, null, constructorCall, true).assignNoPrototype()
+                    statements[i] = DeclarationStatement(listOf(localVar)).assignNoPrototype()
+                    break
+                }
+            }
+        }
+
+        statements.add(ReturnStatement(FactoryFunction.tempValIdentifier()).assignNoPrototype())
+        return statements
+    }
+
     private fun convertInitializer(initializer: PsiClassInitializer): Initializer {
         return Initializer(convertBlock(initializer.getBody()), convertModifiers(initializer)).assignPrototype(initializer)
     }

j2k/tests/testData/ast/class/kt-639.kt

@@ -5,12 +5,10 @@ import java.util.HashMap
 class Test private() {
     class object {
         fun create(): Test {
-            val __ = Test()
-            return __
+            return Test()
         }
         fun create(s: String): Test {
-            val __ = Test()
-            return __
+            return Test()
         }
     }
 }

j2k/tests/testData/ast/comments/commentsForConstructors.kt

@@ -10,8 +10,7 @@ class A// this is a primary constructor
 
         // this is a secondary constructor
         fun create(): A {
-            val __ = A(1)
-            return __
+            return A(1)
         } // end of secondary constructor body
     }
 }

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

@@ -2,13 +2,11 @@ class C(arg1: Int, arg2: Int, arg3: Int) {
     class object {
 
         fun create(arg1: Int, arg2: Int): C {
-            val __ = C(arg1, arg2, 0)
-            return __
+            return C(arg1, arg2, 0)
         }
 
         fun create(arg1: Int): C {
-            val __ = C(arg1, 0, 0)
-            return __
+            return C(arg1, 0, 0)
         }
     }
 }

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

@@ -8,8 +8,7 @@ public class Identifier<T> private(private val myName: T, private val myHasDolla
     class object {
 
         public fun <T> create(name: T): Identifier<T> {
-            val __ = Identifier(name, false)
-            return __
+            return Identifier(name, false)
         }
 
         public fun <T> create(name: T, isNullable: Boolean): Identifier<T> {

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

@@ -8,8 +8,7 @@ public class Identifier private(private val myName: String, private val myHasDol
     class object {
 
         public fun create(name: String): Identifier {
-            val __ = Identifier(name, false)
-            return __
+            return Identifier(name, false)
         }
 
         public fun create(name: String, isNullable: Boolean): Identifier {

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

@@ -20,8 +20,7 @@ class C(arg1: Int, arg2: Int, arg3: Int) {
         }
 
         fun create(arg1: Int): C {
-            val __ = C(arg1, 0, 0)
-            return __
+            return C(arg1, 0, 0)
         }
     }
 }

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

@@ -2,13 +2,11 @@ class C private(arg1: Int, arg2: Int, arg3: Int) {
     class object {
 
         private fun create(arg1: Int, arg2: Int): C {
-            val __ = C(arg1, arg2, 0)
-            return __
+            return C(arg1, arg2, 0)
         }
 
         public fun create(arg1: Int): C {
-            val __ = C(arg1, 0, 0)
-            return __
+            return C(arg1, 0, 0)
         }
     }
 }

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

@@ -2,13 +2,11 @@ public class Test private(private val myName: String, var a: Boolean, var b: Dou
     class object {
 
         public fun create(): Test {
-            val __ = Test(0, false, 0.toDouble(), 0.toFloat(), 0, 0, 0, ' ')
-            return __
+            return Test(0, false, 0.toDouble(), 0.toFloat(), 0, 0, 0, ' ')
         }
 
         public fun create(name: String): Test {
-            val __ = Test(foo(name), false, 0.toDouble(), 0.toFloat(), 0, 0, 0, ' ')
-            return __
+            return Test(foo(name), false, 0.toDouble(), 0.toFloat(), 0, 0, 0, ' ')
         }
 
         fun foo(n: String): String {

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

@@ -8,8 +8,7 @@ public class Identifier<T> private(private val myName: T, private val myHasDolla
     class object {
 
         public fun <T> create(name: T): Identifier<T> {
-            val __ = Identifier(name, false)
-            return __
+            return Identifier(name, false)
         }
 
         public fun <T> create(name: T, isNullable: Boolean): Identifier<T> {