JS: Fixed lateinit property initialization

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java

@@ -3611,6 +3611,12 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
             doTest(fileName);
         }
 
+        @TestMetadata("lateinit.kt")
+        public void testLateinit() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/box/initialize/lateinit.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("propertyInitializationOrder.kt")
         public void testPropertyInitializationOrder() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/box/initialize/propertyInitializationOrder.kt");

js/js.translator/src/org/jetbrains/kotlin/js/translate/initializer/InitializerVisitor.java

@@ -19,8 +19,10 @@ package org.jetbrains.kotlin.js.translate.initializer;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor;
-import org.jetbrains.kotlin.js.backend.ast.*;
-import org.jetbrains.kotlin.js.translate.context.Namer;
+import org.jetbrains.kotlin.js.backend.ast.JsExpression;
+import org.jetbrains.kotlin.js.backend.ast.JsLiteral;
+import org.jetbrains.kotlin.js.backend.ast.JsNameRef;
+import org.jetbrains.kotlin.js.backend.ast.JsStatement;
 import org.jetbrains.kotlin.js.translate.context.TranslationContext;
 import org.jetbrains.kotlin.js.translate.declaration.PropertyTranslatorKt;
 import org.jetbrains.kotlin.js.translate.general.TranslatorVisitor;
@@ -59,13 +61,14 @@ public final class InitializerVisitor extends TranslatorVisitor<Void> {
             statement = generateInitializerForDelegate(descriptor, value);
         }
         else if (Boolean.TRUE.equals(context.bindingContext().get(BindingContext.BACKING_FIELD_REQUIRED, descriptor))) {
-            JsExpression defaultValue = generateDefaultValue(descriptor, context);
+            JsNameRef backingFieldReference = TranslationUtils.backingFieldReference(context, descriptor);
+            JsExpression defaultValue = generateDefaultValue(descriptor, context, backingFieldReference);
             statement = TranslationUtils.assignmentToBackingField(context, descriptor, defaultValue).makeStmt();
         }
         else if (JsDescriptorUtils.isSimpleFinalProperty(descriptor)) {
-            JsExpression defaultValue = generateDefaultValue(descriptor, context);
-            JsName propertyName = context.getNameForDescriptor(descriptor);
-            statement = JsAstUtils.assignment(new JsNameRef(propertyName, JsLiteral.THIS), defaultValue).makeStmt();
+            JsNameRef propRef = new JsNameRef(context.getNameForDescriptor(descriptor), JsLiteral.THIS);
+            JsExpression defaultValue = generateDefaultValue(descriptor, context, propRef);
+            statement = JsAstUtils.assignment(propRef, defaultValue).makeStmt();
         }
 
         if (statement != null && !JsAstUtils.isEmptyStatement(statement)) {
@@ -76,8 +79,11 @@ public final class InitializerVisitor extends TranslatorVisitor<Void> {
     }
 
     @NotNull
-    private static JsExpression generateDefaultValue(@NotNull PropertyDescriptor property, @NotNull TranslationContext context) {
-        if (property.isLateInit()) return Namer.getUndefinedExpression();
+    private static JsExpression generateDefaultValue(
+            @NotNull PropertyDescriptor property,
+            @NotNull TranslationContext context,
+            @NotNull JsExpression lateInitDefault) {
+        if (property.isLateInit()) return lateInitDefault.deepCopy();
 
         KotlinType type = property.getType();
         if (KotlinBuiltIns.isInt(type) || KotlinBuiltIns.isFloat(type) || KotlinBuiltIns.isDouble(type) ||

js/js.translator/testData/box/initialize/lateinit.kt

@@ -0,0 +1,17 @@
+class Greeting {
+    val noon = xrun {
+        verb = "Hello"
+        "World"
+    }
+
+    lateinit var verb: String
+
+    fun greet() = "$verb $noon"
+}
+
+fun <T> xrun(body: () -> T) = body()
+
+fun box(): String {
+    if (Greeting().greet() != "Hello World") return "fail"
+    return "OK"
+}