[JS IR] Fix annotation constructor body generation

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt

@@ -258,11 +258,17 @@ private val primaryConstructorLoweringPhase = makeJsModulePhase(
     prerequisite = setOf(enumClassConstructorLoweringPhase)
 )
 
+private val annotationConstructorLowering = makeJsModulePhase(
+    ::AnnotationConstructorLowering,
+    name = "AnnotationConstructorLowering",
+    description = "Generate annotation constructor body"
+)
+
 private val initializersLoweringPhase = makeJsModulePhase(
     ::InitializersLowering,
     name = "InitializersLowering",
     description = "Merge init block and field initializers into [primary] constructor",
-    prerequisite = setOf(enumClassConstructorLoweringPhase, primaryConstructorLoweringPhase)
+    prerequisite = setOf(enumClassConstructorLoweringPhase, primaryConstructorLoweringPhase, annotationConstructorLowering)
 )
 
 private val multipleCatchesLoweringPhase = makeJsModulePhase(
@@ -397,6 +403,7 @@ val jsPhases = namedIrModulePhase(
             innerClassConstructorCallsLoweringPhase then
             propertiesLoweringPhase then
             primaryConstructorLoweringPhase then
+            annotationConstructorLowering then
             initializersLoweringPhase then
             // Common prefix ends
             enumClassLoweringPhase then

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AnnotationConstructorLowering.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.ir.backend.js.lower
+
+import org.jetbrains.kotlin.backend.common.ClassLoweringPass
+import org.jetbrains.kotlin.backend.common.CommonBackendContext
+import org.jetbrains.kotlin.descriptors.ClassKind
+import org.jetbrains.kotlin.ir.declarations.IrClass
+import org.jetbrains.kotlin.ir.declarations.IrConstructor
+import org.jetbrains.kotlin.ir.expressions.impl.IrBlockBodyImpl
+import org.jetbrains.kotlin.ir.expressions.impl.IrInstanceInitializerCallImpl
+
+class AnnotationConstructorLowering(context: CommonBackendContext) : ClassLoweringPass {
+
+    private val unitType = context.irBuiltIns.unitType
+
+    override fun lower(irClass: IrClass) {
+        if (irClass.kind != ClassKind.ANNOTATION_CLASS) return
+
+        val constructor = irClass.declarations.filterIsInstance<IrConstructor>().single()
+        assert(constructor.isPrimary)
+        // put empty body to make sure proper initializer is generated
+        constructor.body = IrBlockBodyImpl(constructor.startOffset, constructor.endOffset).apply {
+            statements += IrInstanceInitializerCallImpl(startOffset, endOffset, irClass.symbol, unitType)
+        }
+    }
+}