diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt
index c8222e35368..fba07727ac5 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt
@@ -8,12 +8,10 @@ package org.jetbrains.kotlin.ir.backend.js
 import org.jetbrains.kotlin.builtins.PrimitiveType
 import org.jetbrains.kotlin.ir.IrBuiltIns
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
-import org.jetbrains.kotlin.ir.backend.js.utils.getJsName
 import org.jetbrains.kotlin.ir.declarations.IrFunction
 import org.jetbrains.kotlin.ir.declarations.IrProperty
 import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
-import org.jetbrains.kotlin.ir.symbols.IrConstructorSymbol
 import org.jetbrains.kotlin.ir.symbols.IrSimpleFunctionSymbol
 import org.jetbrains.kotlin.ir.types.isLong
 import org.jetbrains.kotlin.ir.util.constructors
@@ -109,6 +107,9 @@ class JsIntrinsics(private val irBuiltIns: IrBuiltIns, val context: JsIrBackendC
 
 
     // RTTI:
+    val implementSymbol = getInternalFunction("implement")
+    val setMetadataForSymbol = getInternalFunction("setMetadataFor")
+
     val isInterfaceSymbol = getInternalFunction("isInterface")
     val isArraySymbol = getInternalFunction("isArray")
     //    val isCharSymbol = getInternalFunction("isChar")
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
index 9cb95504339..0b7a384e001 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt
@@ -155,6 +155,7 @@ class JsIrBackendContext(
 
     val dynamicType: IrDynamicType = IrDynamicTypeImpl(null, emptyList(), Variance.INVARIANT)
     val intrinsics: JsIntrinsics = JsIntrinsics(irBuiltIns, this)
+
     override val reflectionSymbols: ReflectionSymbols get() = intrinsics.reflectionSymbols
 
     override val propertyLazyInitialization: PropertyLazyInitialization = PropertyLazyInitialization(
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
index 7cd1de294db..2b22aa49d89 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
@@ -526,7 +526,7 @@ private val privateMemberUsagesLoweringPhase = makeBodyLoweringPhase(
 private val propertyReferenceLoweringPhase = makeBodyLoweringPhase(
     ::PropertyReferenceLowering,
     name = "PropertyReferenceLowering",
-    description = "Transform property references"
+    description = "Transform property references",
 )
 
 private val interopCallableReferenceLoweringPhase = makeBodyLoweringPhase(
@@ -669,7 +669,7 @@ private val typeOperatorLoweringPhase = makeBodyLoweringPhase(
         bridgesConstructionPhase,
         removeInlineDeclarationsWithReifiedTypeParametersLoweringPhase,
         singleAbstractMethodPhase, errorExpressionLoweringPhase,
-        interopCallableReferenceLoweringPhase
+        interopCallableReferenceLoweringPhase,
     )
 )
 
@@ -705,7 +705,6 @@ private val constLoweringPhase = makeBodyLoweringPhase(
     name = "ConstLowering",
     description = "Wrap Long and Char constants into constructor invocation"
 )
-
 private val inlineClassDeclarationLoweringPhase = makeDeclarationTransformerPhase(
     { InlineClassLowering(it).inlineClassDeclarationLowering },
     name = "InlineClassDeclarationLowering",
@@ -806,6 +805,7 @@ private val implicitlyExportedDeclarationsMarkingLowering = makeDeclarationTrans
     description = "Add @JsImplicitExport annotation to declarations which are not exported but are used inside other exported declarations as a type"
 )
 
+
 private val cleanupLoweringPhase = makeBodyLoweringPhase(
     { CleanupLowering() },
     name = "CleanupLowering",
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt
index 387d6d2808c..73c15b0fe9d 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt
@@ -5,22 +5,17 @@
 
 package org.jetbrains.kotlin.ir.backend.js.dce
 
+import org.jetbrains.kotlin.backend.common.lower.MethodsFromAnyGeneratorForLowerings.Companion.collectOverridenSymbols
 import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
 import org.jetbrains.kotlin.ir.backend.js.JsStatementOrigins
 import org.jetbrains.kotlin.ir.backend.js.export.isExported
 import org.jetbrains.kotlin.ir.backend.js.lower.isBuiltInClass
-import org.jetbrains.kotlin.ir.backend.js.utils.associatedObject
-import org.jetbrains.kotlin.ir.backend.js.utils.getJsName
-import org.jetbrains.kotlin.ir.backend.js.utils.getJsNameOrKotlinName
-import org.jetbrains.kotlin.ir.backend.js.utils.invokeFunForLambda
+import org.jetbrains.kotlin.ir.backend.js.utils.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.IrCall
-import org.jetbrains.kotlin.ir.expressions.IrGetObjectValue
+import org.jetbrains.kotlin.ir.expressions.IrFunctionAccessExpression
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
-import org.jetbrains.kotlin.ir.types.classOrNull
-import org.jetbrains.kotlin.ir.types.classifierOrFail
-import org.jetbrains.kotlin.ir.types.classifierOrNull
-import org.jetbrains.kotlin.ir.types.getClass
+import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 
 internal class JsUsefulDeclarationProcessor(
@@ -33,6 +28,13 @@ internal class JsUsefulDeclarationProcessor(
     private val hashCodeMethod = getMethodOfAny("hashCode")
 
     override val bodyVisitor: BodyVisitorBase = object : BodyVisitorBase() {
+        override fun visitFunctionAccess(expression: IrFunctionAccessExpression, data: IrDeclaration) {
+            if (expression.symbol != context.intrinsics.implementSymbol) {
+                // Just ignore implement to not include large chunk of code inside small applications if it's not needed
+                super.visitFunctionAccess(expression, data)
+            }
+        }
+
         override fun visitCall(expression: IrCall, data: IrDeclaration) {
             super.visitCall(expression, data)
             when (expression.symbol) {
@@ -113,20 +115,41 @@ internal class JsUsefulDeclarationProcessor(
 
     }
 
+    override fun processSuperTypes(irClass: IrClass) {
+        irClass.superTypes.forEach {
+            if (!it.isInterface()) {
+                (it.classifierOrNull as? IrClassSymbol)?.owner?.enqueue(irClass, "superTypes")
+            }
+        }
+    }
+
     override fun processClass(irClass: IrClass) {
         super.processClass(irClass)
 
         if (irClass.containsMetadata()) {
             when {
-                irClass.isInterface -> context.intrinsics.metadataInterfaceConstructorSymbol.owner.enqueue(irClass, "interface metadata")
                 irClass.isObject -> context.intrinsics.metadataObjectConstructorSymbol.owner.enqueue(irClass, "object metadata")
+                irClass.isInterface -> {
+                    context.intrinsics.implementSymbol.owner.enqueue(irClass, "interface metadata")
+                    context.intrinsics.metadataInterfaceConstructorSymbol.owner.enqueue(irClass, "interface metadata")
+                }
                 else -> context.intrinsics.metadataClassConstructorSymbol.owner.enqueue(irClass, "class metadata")
             }
+
+            context.intrinsics.setMetadataForSymbol.owner.enqueue(irClass, "metadata")
+        }
+    }
+
+    override fun processSimpleFunction(irFunction: IrSimpleFunction) {
+        super.processSimpleFunction(irFunction)
+
+        if (irFunction.isReal && irFunction.body != null) {
+            irFunction.parentClassOrNull?.takeIf { it.isInterface }?.enqueue(irFunction, "interface default method is used")
         }
     }
 
     private fun IrClass.containsMetadata(): Boolean =
-        !isExternal && !isExpect &&  !isBuiltInClass(this)
+        !isExternal && !isExpect && !isBuiltInClass(this)
 
     override fun processConstructedClassDeclaration(declaration: IrDeclaration) {
         if (declaration in result) return
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UsefulDeclarationProcessor.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UsefulDeclarationProcessor.kt
index 11f9f1856b5..3636b7be166 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UsefulDeclarationProcessor.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UsefulDeclarationProcessor.kt
@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.ir.backend.js.utils.isAssociatedObjectAnnotatedAnnot
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
+import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.classifierOrNull
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
@@ -138,14 +139,12 @@ abstract class UsefulDeclarationProcessor(
     protected val result = hashSetOf<IrDeclaration>()
     protected val classesWithObjectAssociations = hashSetOf<IrClass>()
 
-    public val usefulPolyfilledDeclarations = hashSetOf<IrDeclaration>()
+    val usefulPolyfilledDeclarations = hashSetOf<IrDeclaration>()
 
     protected open fun processField(irField: IrField): Unit = Unit
 
     protected open fun processClass(irClass: IrClass) {
-        irClass.superTypes.forEach {
-            (it.classifierOrNull as? IrClassSymbol)?.owner?.enqueue(irClass, "superTypes")
-        }
+        processSuperTypes(irClass)
 
         if (irClass.isObject && isExported(irClass)) {
             context.mapping.objectToGetInstanceFunction[irClass]
@@ -161,6 +160,12 @@ abstract class UsefulDeclarationProcessor(
         }
     }
 
+    protected open fun processSuperTypes(irClass: IrClass) {
+        irClass.superTypes.forEach {
+            (it.classifierOrNull as? IrClassSymbol)?.owner?.enqueue(irClass, "superTypes")
+        }
+    }
+
     protected open fun processSimpleFunction(irFunction: IrSimpleFunction) {
         if (irFunction.isFakeOverride) {
             irFunction.resolveFakeOverride()?.enqueue(irFunction, "real overridden fun", isContagious = false)
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UselessDeclarationsRemover.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UselessDeclarationsRemover.kt
index 0dc878f4d44..a6335593944 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UselessDeclarationsRemover.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UselessDeclarationsRemover.kt
@@ -13,6 +13,11 @@ import org.jetbrains.kotlin.ir.backend.js.ir.JsIrBuilder
 import org.jetbrains.kotlin.ir.backend.js.utils.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
+import org.jetbrains.kotlin.ir.types.IrType
+import org.jetbrains.kotlin.ir.types.classOrNull
+import org.jetbrains.kotlin.ir.types.defaultType
+import org.jetbrains.kotlin.ir.types.isAny
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
 import org.jetbrains.kotlin.ir.visitors.acceptVoid
@@ -24,6 +29,8 @@ class UselessDeclarationsRemover(
     private val context: JsIrBackendContext,
     private val dceRuntimeDiagnostic: RuntimeDiagnostic?,
 ) : IrElementVisitorVoid {
+    private val savedTypesCache = hashMapOf<IrClassSymbol, Set<IrClassSymbol>>()
+
     override fun visitElement(element: IrElement) {
         element.acceptChildrenVoid(this)
     }
@@ -47,6 +54,23 @@ class UselessDeclarationsRemover(
         if (removeUnusedAssociatedObjects && declaration.annotations.any { !it.shouldKeepAnnotation() }) {
             declaration.annotations = declaration.annotations.filter { it.shouldKeepAnnotation() }
         }
+
+        declaration.superTypes = declaration.superTypes
+            .flatMap { it.classOrNull?.collectUsedSuperTypes() ?: emptyList() }
+            .distinct()
+            .map { it.defaultType }
+    }
+
+    private fun IrClassSymbol.collectUsedSuperTypes(): Set<IrClassSymbol> {
+        return savedTypesCache.getOrPut(this) {
+            if (owner in usefulDeclarations) {
+                setOf(this)
+            } else {
+                owner.superTypes
+                    .flatMap { it.takeIf { !it.isAny() }?.classOrNull?.collectUsedSuperTypes() ?: emptyList() }
+                    .toSet()
+            }
+        }
     }
 
     // TODO bring back the primary constructor fix
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
index bc03b5295b3..1eef2058bb6 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrElementToJsExpressionTransformer.kt
@@ -128,8 +128,8 @@ class IrElementToJsExpressionTransformer : BaseIrElementToJsNodeTransformer<JsEx
     override fun visitGetObjectValue(expression: IrGetObjectValue, context: JsGenerationContext): JsExpression {
         val obj = expression.symbol.owner
 
-         assert(obj.kind == ClassKind.OBJECT)
-         assert(obj.isEffectivelyExternal()) { "Non external IrGetObjectValue must be lowered" }
+        assert(obj.kind == ClassKind.OBJECT)
+        assert(obj.isEffectivelyExternal()) { "Non external IrGetObjectValue must be lowered" }
 
         return context.getRefForExternalClass(obj).withSource(expression, context)
     }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformerTmp.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformerTmp.kt
index c914de57869..0dff12e6cad 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformerTmp.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformerTmp.kt
@@ -269,7 +269,7 @@ class IrModuleToJsTransformerTmp(
 
         staticContext.classModels.entries.forEach { (symbol, model) ->
             result.classes[nameGenerator.getNameForClass(symbol.owner)] =
-                JsIrIcClassModel(model.klass.superTypes.map { staticContext.getNameForClass((it.classifierOrFail as IrClassSymbol).owner) }).also {
+                JsIrIcClassModel(model.superClasses.map { staticContext.getNameForClass(it.owner) }).also {
                     it.preDeclarationBlock.statements += model.preDeclarationBlock.statements
                     it.postDeclarationBlock.statements += model.postDeclarationBlock.statements
                 }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt
index f86a925f660..89f9908d609 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/JsClassGenerator.kt
@@ -6,27 +6,31 @@
 package org.jetbrains.kotlin.ir.backend.js.transformers.irToJs
 
 import org.jetbrains.kotlin.backend.common.compilationException
+import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
 import org.jetbrains.kotlin.descriptors.Modality
+import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
 import org.jetbrains.kotlin.ir.backend.js.export.isAllowedFakeOverriddenDeclaration
 import org.jetbrains.kotlin.ir.backend.js.export.isExported
 import org.jetbrains.kotlin.ir.backend.js.export.isOverriddenExported
 import org.jetbrains.kotlin.ir.backend.js.utils.*
+import org.jetbrains.kotlin.ir.builders.irCall
 import org.jetbrains.kotlin.ir.declarations.*
+import org.jetbrains.kotlin.ir.expressions.IrClassReference
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.impl.IrVarargImpl
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.symbols.IrClassifierSymbol
-import org.jetbrains.kotlin.ir.types.IrType
-import org.jetbrains.kotlin.ir.types.classifierOrFail
-import org.jetbrains.kotlin.ir.types.classifierOrNull
-import org.jetbrains.kotlin.ir.types.isAny
+import org.jetbrains.kotlin.ir.symbols.IrSimpleFunctionSymbol
+import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.js.backend.ast.*
 import org.jetbrains.kotlin.js.common.isValidES5Identifier
 import org.jetbrains.kotlin.utils.addIfNotNull
+import org.jetbrains.kotlin.utils.addToStdlib.runIf
 
 class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationContext) {
-
     private val className = context.getNameForClass(irClass)
     private val classNameRef = className.makeRef()
     private val baseClass: IrType? = irClass.superTypes.firstOrNull { !it.classifierOrFail.isInterface }
@@ -44,6 +48,7 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
         assert(!irClass.isExpect)
 
         if (!es6mode) maybeGeneratePrimaryConstructor()
+
         val transformer = IrDeclarationToJsTransformer()
 
         // Properties might be lowered out of classes
@@ -74,7 +79,6 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
                         }
                     } else {
                         classBlock.statements += declaration.accept(transformer, context)
-                        classModel.preDeclarationBlock.statements += generateInheritanceCode()
                     }
                 }
                 is IrSimpleFunction -> {
@@ -104,8 +108,6 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
             }
         }
 
-        classBlock.statements += generateClassMetadata()
-
         if (!irClass.isInterface) {
             for (property in properties) {
                 if (property.getter?.extensionReceiverParameter != null || property.setter?.extensionReceiverParameter != null)
@@ -206,7 +208,11 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
                 }
             }
         }
+
+        classModel.preDeclarationBlock.statements += generateSetMetadataCall()
+
         context.staticContext.classModels[irClass.symbol] = classModel
+
         return classBlock
     }
 
@@ -307,24 +313,49 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
             val func = JsFunction(emptyScope, JsBlock(), "Ctor for ${irClass.name}")
             func.name = className
             classBlock.statements += func.makeStmt()
-            classModel.preDeclarationBlock.statements += generateInheritanceCode()
         }
     }
 
-    private fun generateInheritanceCode(): List<JsStatement> {
-        val baseClassPrototype = baseClassRef ?: return emptyList()
+    private fun generateSetMetadataCall(): JsStatement {
+        val setMetadataFor = context.staticContext.backendContext.intrinsics.setMetadataForSymbol.owner
 
-        val createCall = jsAssignment(
-            classPrototypeRef, JsInvocation(Namer.JS_OBJECT_CREATE_FUNCTION, prototypeOf(baseClassPrototype))
+        val ctor = classNameRef
+        val parent = baseClassRef
+        val name = generateSimpleName()
+        val interfaces = generateInterfacesList()
+        val metadataConstructor = getMetadataConstructor()
+        val associatedObjectKey = generateAssociatedObjectKey()
+        val associatedObjects = generateAssociatedObjects()
+        val suspendArity = generateSuspendArity()
+
+        return JsInvocation(
+            JsNameRef(context.getNameForStaticFunction(setMetadataFor)),
+            listOf(ctor, name, metadataConstructor, parent, interfaces, associatedObjectKey, associatedObjects, suspendArity)
+                .dropLastWhile { it == null }
+                .map { it ?: Namer.JS_UNDEFINED }
         ).makeStmt()
 
-        val ctorAssign = jsAssignment(JsNameRef(Namer.CONSTRUCTOR_NAME, classPrototypeRef), classNameRef).makeStmt()
-
-        return listOf(createCall, ctorAssign)
     }
 
-    private fun generateClassMetadata(): JsStatement {
-        val metadataConstructor = with(context.staticContext.backendContext.intrinsics) {
+
+    private fun IrType.asConstructorRef(): JsNameRef? {
+        val ownerSymbol = classOrNull?.takeIf {
+            !isAny() && !isFunctionType() && !it.owner.isEffectivelyExternal()
+        } ?: return null
+
+        return JsNameRef(context.getNameForClass(ownerSymbol.owner))
+    }
+
+    private fun IrType.isFunctionType() = isFunctionOrKFunction() || isSuspendFunctionOrKFunction()
+
+    private fun isCoroutineClass(): Boolean = irClass.superTypes.any { it.isSuspendFunctionTypeOrSubtype() }
+
+    private fun generateSimpleName(): JsStringLiteral? {
+        return irClass.name.takeIf { !it.isSpecial }?.let { JsStringLiteral(it.identifier) }
+    }
+
+    private fun getMetadataConstructor(): JsNameRef {
+        val metadataConstructorSymbol = with(context.staticContext.backendContext.intrinsics) {
             when {
                 irClass.isInterface -> metadataInterfaceConstructorSymbol
                 irClass.isObject -> metadataObjectConstructorSymbol
@@ -332,32 +363,21 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
             }
         }
 
-        val simpleName = irClass.name
-            .takeIf { !it.isSpecial }
-            ?.let { JsStringLiteral(it.identifier) }
-
-        val interfaces = generateSuperClasses()
-        val associatedObjectKey = generateAssociatedObjectKey()
-        val associatedObjects = generateAssociatedObjects()
-        val fastPrototype = generateFastPrototype()
-        val suspendArity = generateSuspendArity()
-
-        val constructorCall = JsInvocation(
-            JsNameRef(context.getNameForStaticFunction(metadataConstructor.owner)),
-            listOf(simpleName, interfaces, associatedObjectKey, associatedObjects, suspendArity, fastPrototype)
-                .dropLastWhile { it == null }
-                .map { it ?: Namer.JS_UNDEFINED }
-        )
-
-        return jsAssignment(JsNameRef(Namer.METADATA, classNameRef), constructorCall).makeStmt()
+        return JsNameRef(context.getNameForStaticFunction(metadataConstructorSymbol.owner))
     }
 
-    private fun isCoroutineClass(): Boolean = irClass.superTypes.any { it.isSuspendFunctionTypeOrSubtype() }
+    private fun generateInterfacesList(): JsArrayLiteral? {
+        val listRef = irClass.superTypes
+            .filter { it.classOrNull?.owner?.isExternal != true }
+            .takeIf { it.size > 1 || it.singleOrNull() != baseClass }
+            ?.mapNotNull { it.asConstructorRef() }
+            ?.takeIf { it.isNotEmpty() } ?: return null
+        return JsArrayLiteral(listRef)
+    }
 
     private fun generateSuspendArity(): JsArrayLiteral? {
-        if (!isCoroutineClass()) return null
-
-        val arity = context.staticContext.backendContext.mapping.suspendArityStore[irClass]!!
+        val invokeFunctions = context.staticContext.backendContext.mapping.suspendArityStore[irClass] ?: return null
+        val arity = invokeFunctions
             .map { it.valueParameters.size }
             .distinct()
             .map { JsIntLiteral(it) }
@@ -365,30 +385,6 @@ class JsClassGenerator(private val irClass: IrClass, val context: JsGenerationCo
         return JsArrayLiteral(arity)
     }
 
-    private fun generateSuperClasses(): JsArrayLiteral? {
-        val parentSymbols = irClass.superTypes.mapNotNull {
-            val symbol = it.classifierOrFail as IrClassSymbol
-            val isFunctionType = it.isFunctionType()
-            // TODO: make sure that there is a test which breaks when isExternal is used here instead of isEffectivelyExternal
-            val requireInMetadata = if (context.staticContext.backendContext.baseClassIntoMetadata)
-                !it.isAny()
-            else
-                symbol.isInterface
-
-            if (requireInMetadata && !isFunctionType && !symbol.isEffectivelyExternal) {
-                symbol
-            } else null
-        }
-
-        return parentSymbols
-            .takeIf { it.isNotEmpty() }
-            ?.run { JsArrayLiteral(map { JsNameRef(context.getNameForClass(it.owner)) }) }
-    }
-
-    private fun generateFastPrototype() = baseClassRef?.let { prototypeOf(it) }
-
-    private fun IrType.isFunctionType() = isFunctionOrKFunction() || isSuspendFunctionOrKFunction()
-
     private fun generateAssociatedObjectKey(): JsIntLiteral? {
         return context.getAssociatedObjectKey(irClass)?.let { JsIntLiteral(it) }
     }
@@ -440,10 +436,9 @@ private fun IrOverridableDeclaration<*>.overridesExternal(): Boolean {
 }
 
 private val IrClassifierSymbol.isInterface get() = (owner as? IrClass)?.isInterface == true
-private val IrClassifierSymbol.isEffectivelyExternal get() = (owner as? IrDeclaration)?.isEffectivelyExternal() == true
 
 class JsIrClassModel(val klass: IrClass) {
-    val superClasses = klass.superTypes.map { it.classifierOrFail as IrClassSymbol }
+    val superClasses = klass.superTypes.map { it.classifierOrNull as IrClassSymbol }
 
     val preDeclarationBlock = JsCompositeBlock()
     val postDeclarationBlock = JsCompositeBlock()
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/Merger.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/Merger.kt
index bd6e437fca6..e894b092b34 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/Merger.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/Merger.kt
@@ -272,7 +272,7 @@ class Merger(
 
         DFS.dfs(
             classModelMap.keys,
-            { klass -> classModelMap[klass]?.superClasses ?: emptyList() },
+            { classModelMap[it]?.superClasses ?: emptyList() },
             declarationHandler
         )
     }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/AnnotationUtils.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/AnnotationUtils.kt
index 8c216d807f0..f0aa7585b7f 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/AnnotationUtils.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/AnnotationUtils.kt
@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.ir.declarations.IrOverridableDeclaration
 import org.jetbrains.kotlin.ir.expressions.IrClassReference
 import org.jetbrains.kotlin.ir.expressions.IrConst
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
+import org.jetbrains.kotlin.ir.expressions.IrVararg
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.name.FqName
@@ -36,8 +37,8 @@ fun IrConstructorCall.getSingleConstStringArgument() =
     (getValueArgument(0) as IrConst<String>).value
 
 @Suppress("UNCHECKED_CAST")
-fun IrConstructorCall.getSingleConstBooleanArgument() =
-    (getValueArgument(0) as IrConst<Boolean>).value
+fun IrConstructorCall.getClassReferencVarargArguments() =
+    (getValueArgument(0) as? IrVararg)?.elements as? List<IrClassReference>
 
 fun IrAnnotationContainer.getJsModule(): String? =
     getAnnotation(JsAnnotations.jsModuleFqn)?.getSingleConstStringArgument()
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/Namer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/Namer.kt
index 45deddf8111..ab5e228e1e9 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/Namer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/Namer.kt
@@ -32,7 +32,7 @@ object Namer {
     val JS_OBJECT_CREATE_FUNCTION = JsNameRef("create", JS_OBJECT)
 
     val METADATA = "\$metadata\$"
-    val METADATA_INTERFACE_ID = "interfaceId"
+    val INTERFACES_MASK = "\$imask\$"
 
     val KCALLABLE_GET_NAME = "<get-name>"
     val KCALLABLE_NAME = "callableName"
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/BoxJsTestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/BoxJsTestGenerated.java
index dbf6778ff9c..dec9edc11fd 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/BoxJsTestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/BoxJsTestGenerated.java
@@ -3811,6 +3811,12 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
                 KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("js/js.translator/testData/box/expression/typeCheck"), Pattern.compile("^([^_](.+))\\.kt$"), null, TargetBackend.JS, true);
             }
 
+            @Test
+            @TestMetadata("complexIsInterface.kt")
+            public void testComplexIsInterface() throws Exception {
+                runTest("js/js.translator/testData/box/expression/typeCheck/complexIsInterface.kt");
+            }
+
             @Test
             @TestMetadata("simpleAsClass.kt")
             public void testSimpleAsClass() throws Exception {
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/FirJsTestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/FirJsTestGenerated.java
index 7527a27af55..7402db3f8c3 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/FirJsTestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/FirJsTestGenerated.java
@@ -4265,6 +4265,12 @@ public class FirJsTestGenerated extends AbstractFirJsTest {
                 KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("js/js.translator/testData/box/expression/typeCheck"), Pattern.compile("^([^_](.+))\\.kt$"), null, TargetBackend.JS_IR, true);
             }
 
+            @Test
+            @TestMetadata("complexIsInterface.kt")
+            public void testComplexIsInterface() throws Exception {
+                runTest("js/js.translator/testData/box/expression/typeCheck/complexIsInterface.kt");
+            }
+
             @Test
             @TestMetadata("simpleAsClass.kt")
             public void testSimpleAsClass() throws Exception {
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsTestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsTestGenerated.java
index bcc53878e13..b0081e47b14 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsTestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrBoxJsTestGenerated.java
@@ -4265,6 +4265,12 @@ public class IrBoxJsTestGenerated extends AbstractIrBoxJsTest {
                 KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("js/js.translator/testData/box/expression/typeCheck"), Pattern.compile("^([^_](.+))\\.kt$"), null, TargetBackend.JS_IR, true);
             }
 
+            @Test
+            @TestMetadata("complexIsInterface.kt")
+            public void testComplexIsInterface() throws Exception {
+                runTest("js/js.translator/testData/box/expression/typeCheck/complexIsInterface.kt");
+            }
+
             @Test
             @TestMetadata("simpleAsClass.kt")
             public void testSimpleAsClass() throws Exception {
diff --git a/js/js.translator/testData/box/expression/typeCheck/complexIsInterface.kt b/js/js.translator/testData/box/expression/typeCheck/complexIsInterface.kt
new file mode 100644
index 00000000000..6987ba7f9b7
--- /dev/null
+++ b/js/js.translator/testData/box/expression/typeCheck/complexIsInterface.kt
@@ -0,0 +1,219 @@
+// WITH_STDLIB
+
+package foo
+
+interface I1: I61
+interface I2: I61, I62
+interface I3: I61, I62, I63
+interface I4: I61, I62, I63, I64
+interface I5: I61, I62, I63, I64, I65
+interface I6: I61, I62, I63, I64, I65, I66
+interface I7: I61, I62, I63, I64, I65, I66, I67
+interface I8: I61, I62, I63, I64, I65, I66, I67, I68
+interface I9: I61, I62, I63, I64, I65, I66, I67, I68, I69
+interface I10: I61, I62, I63, I64, I65, I66, I67, I68, I69, I70
+
+interface I11: I51, I52, I53, I54, I55, I56, I57, I58, I59, I60
+interface I12: I51, I52, I53, I54, I55, I56, I57, I58, I59
+interface I13: I51, I52, I53, I54, I55, I56, I57, I58
+interface I14: I51, I52, I53, I54, I55, I56, I57
+interface I15: I51, I52, I53, I54, I55, I56
+interface I16: I51, I52, I53, I54, I55
+interface I17: I51, I52, I53, I54
+interface I18: I51, I52, I53
+interface I19: I51, I52
+interface I20: I51
+
+interface I21
+interface I22: I21
+interface I23: I22
+interface I24: I23
+interface I25: I24
+interface I26: I25
+interface I27: I26
+interface I28: I27
+interface I29: I28
+interface I30: I29
+
+interface I31: I40
+interface I32: I37
+interface I33: I36
+interface I34: I35
+interface I35
+interface I36: I34
+interface I37: I33
+interface I38: I32
+interface I39: I31
+interface I40
+
+interface I41: I1
+interface I42: I1, I2
+interface I43: I1, I2, I3
+interface I44: I1, I2, I3, I4
+interface I45: I1, I2, I3, I4, I5
+interface I46: I1, I2, I3, I4, I5, I6
+interface I47: I1, I2, I3, I4, I5, I6, I7
+interface I48: I1, I2, I3, I4, I5, I6, I7, I8
+interface I49: I1, I2, I3, I4, I5, I6, I7, I8, I9
+interface I50: I1, I2, I3, I4, I5, I6, I7, I8, I9, I10
+
+interface I51: I10
+interface I52: I20
+interface I53: I30
+interface I54: I40
+interface I55: I50
+interface I56: I60
+interface I57: I70
+interface I58
+interface I59
+interface I60
+
+interface I61
+interface I62
+interface I63
+interface I64
+interface I65
+interface I66
+interface I67
+interface I68
+interface I69
+interface I70
+
+open class C1: I51
+open class C2: C1(), I52
+open class C3: C2(), I53
+open class C4: C3(), I54
+open class C5: C4(), I55
+open class C6: C5(), I56
+open class C7: C6(), I57
+open class C8: C7() // SKIP I58
+open class C9: C8() // SKIP I59
+class C10: C9(), I60
+
+class C11: I1, I11
+class C12: I2, I12
+class C13: I3, I13
+class C14: I4, I14
+class C15: I5, I15
+class C16: I6, I16
+class C17: I7, I17
+class C18: I8, I18
+class C19: I9, I19
+class C20: I10, I20
+
+open class C21: I31, I32, I33
+class C22: C21(), I34, I35, I36
+open class C23: I37, I38, I39
+class C24: C23(), I40, I50, I60
+class C25
+
+fun process(instance: Any, label: String, interfaces: Set<String>) {
+    assertEquals("I1" in interfaces, instance is I1, "$label is I1")
+    assertEquals("I2" in interfaces, instance is I2, "$label is I2")
+    assertEquals("I3" in interfaces, instance is I3, "$label is I3")
+    assertEquals("I4" in interfaces, instance is I4, "$label is I4")
+    assertEquals("I5" in interfaces, instance is I5, "$label is I5")
+    assertEquals("I6" in interfaces, instance is I6, "$label is I6")
+    assertEquals("I7" in interfaces, instance is I7, "$label is I7")
+    assertEquals("I8" in interfaces, instance is I8, "$label is I8")
+    assertEquals("I9" in interfaces, instance is I9, "$label is I9")
+    assertEquals("I10" in interfaces, instance is I10, "$label is I10")
+
+    assertEquals("I11" in interfaces, instance is I11, "$label is I11")
+    assertEquals("I12" in interfaces, instance is I12, "$label is I12")
+    assertEquals("I13" in interfaces, instance is I13, "$label is I13")
+    assertEquals("I14" in interfaces, instance is I14, "$label is I14")
+    assertEquals("I15" in interfaces, instance is I15, "$label is I15")
+    assertEquals("I16" in interfaces, instance is I16, "$label is I16")
+    assertEquals("I17" in interfaces, instance is I17, "$label is I17")
+    assertEquals("I18" in interfaces, instance is I18, "$label is I18")
+    assertEquals("I19" in interfaces, instance is I19, "$label is I19")
+    assertEquals("I20" in interfaces, instance is I20, "$label is I20")
+
+    assertEquals("I21" in interfaces, instance is I21, "$label is I21")
+    assertEquals("I22" in interfaces, instance is I22, "$label is I22")
+    assertEquals("I23" in interfaces, instance is I23, "$label is I23")
+    assertEquals("I24" in interfaces, instance is I24, "$label is I24")
+    assertEquals("I25" in interfaces, instance is I25, "$label is I25")
+    assertEquals("I26" in interfaces, instance is I26, "$label is I26")
+    assertEquals("I27" in interfaces, instance is I27, "$label is I27")
+    assertEquals("I28" in interfaces, instance is I28, "$label is I28")
+    assertEquals("I29" in interfaces, instance is I29, "$label is I29")
+    assertEquals("I30" in interfaces, instance is I30, "$label is I30")
+
+    assertEquals("I31" in interfaces, instance is I31, "$label is I31")
+    assertEquals("I32" in interfaces, instance is I32, "$label is I32")
+    assertEquals("I33" in interfaces, instance is I33, "$label is I33")
+    assertEquals("I34" in interfaces, instance is I34, "$label is I34")
+    assertEquals("I35" in interfaces, instance is I35, "$label is I35")
+    assertEquals("I36" in interfaces, instance is I36, "$label is I36")
+    assertEquals("I37" in interfaces, instance is I37, "$label is I37")
+    assertEquals("I38" in interfaces, instance is I38, "$label is I38")
+    assertEquals("I39" in interfaces, instance is I39, "$label is I39")
+    assertEquals("I40" in interfaces, instance is I40, "$label is I40")
+
+    assertEquals("I41" in interfaces, instance is I41, "$label is I41")
+    assertEquals("I42" in interfaces, instance is I42, "$label is I42")
+    assertEquals("I43" in interfaces, instance is I43, "$label is I43")
+    assertEquals("I44" in interfaces, instance is I44, "$label is I44")
+    assertEquals("I45" in interfaces, instance is I45, "$label is I45")
+    assertEquals("I46" in interfaces, instance is I46, "$label is I46")
+    assertEquals("I47" in interfaces, instance is I47, "$label is I47")
+    assertEquals("I48" in interfaces, instance is I48, "$label is I48")
+    assertEquals("I49" in interfaces, instance is I49, "$label is I49")
+    assertEquals("I50" in interfaces, instance is I50, "$label is I50")
+
+    assertEquals("I51" in interfaces, instance is I51, "$label is I51")
+    assertEquals("I52" in interfaces, instance is I52, "$label is I52")
+    assertEquals("I53" in interfaces, instance is I53, "$label is I53")
+    assertEquals("I54" in interfaces, instance is I54, "$label is I54")
+    assertEquals("I55" in interfaces, instance is I55, "$label is I55")
+    assertEquals("I56" in interfaces, instance is I56, "$label is I56")
+    assertEquals("I57" in interfaces, instance is I57, "$label is I57")
+    assertEquals("I58" in interfaces, instance is I58, "$label is I58")
+    assertEquals("I59" in interfaces, instance is I59, "$label is I59")
+    assertEquals("I60" in interfaces, instance is I60, "$label is I60")
+
+    assertEquals("I61" in interfaces, instance is I61, "$label is I61")
+    assertEquals("I62" in interfaces, instance is I62, "$label is I62")
+    assertEquals("I63" in interfaces, instance is I63, "$label is I63")
+    assertEquals("I64" in interfaces, instance is I64, "$label is I64")
+    assertEquals("I65" in interfaces, instance is I65, "$label is I65")
+    assertEquals("I66" in interfaces, instance is I66, "$label is I66")
+    assertEquals("I67" in interfaces, instance is I67, "$label is I67")
+    assertEquals("I68" in interfaces, instance is I68, "$label is I68")
+    assertEquals("I69" in interfaces, instance is I69, "$label is I69")
+    assertEquals("I70" in interfaces, instance is I70, "$label is I70")
+}
+
+fun box(): String {
+    process(C1(), "C1", setOf("I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C2(), "C2", setOf("I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C3(), "C3", setOf("I53", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C4(), "C4", setOf("I54", "I40", "I53", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C5(), "C5", setOf("I55", "I50", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I54", "I40", "I53", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C6(), "C6", setOf("I56", "I60", "I55", "I50", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I54", "I40", "I53", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C7(), "C7", setOf("I57", "I56", "I60", "I55", "I50", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I54", "I40", "I53", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C8(), "C8", setOf("I57", "I56", "I60", "I55", "I50", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I54", "I40", "I53", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C9(), "C9", setOf("I57", "I56", "I60", "I55", "I50", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I54", "I40", "I53", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C10(), "C10", setOf("I57", "I56", "I60", "I55", "I50", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I54", "I40", "I53", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I52", "I20", "I51", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+
+    process(C11(), "C11", setOf("I1", "I61", "I11", "I51", "I52", "I53", "I54", "I55", "I56", "I57", "I58", "I59", "I60", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70", "I10", "I20", "I30", "I40", "I50", "I60", "I70", "I21", "I22", "I23", "I24", "I25", "I26", "I27", "I28", "I29", "I30", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10"))
+    process(C12(), "C12", setOf("I2", "I61", "I62", "I12", "I51", "I52", "I53", "I54", "I55", "I56", "I57", "I58", "I59", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70", "I10", "I20", "I30", "I40", "I50", "I70", "I21", "I22", "I23", "I24", "I25", "I26", "I27", "I28", "I29", "I30", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I60"))
+    process(C13(), "C13", setOf("I3", "I13", "I61", "I62", "I63", "I51", "I52", "I53", "I54", "I55", "I56", "I57", "I58", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70", "I10", "I20", "I30", "I40", "I50", "I70", "I21", "I22", "I23", "I24", "I25", "I26", "I27", "I28", "I29", "I30", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I60"))
+    process(C14(), "C14", setOf("I4", "I14", "I61", "I62", "I63", "I64", "I51", "I52", "I53", "I54", "I55", "I56", "I57", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70", "I10", "I20", "I30", "I40", "I50", "I70", "I21", "I22", "I23", "I24", "I25", "I26", "I27", "I28", "I29", "I30", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I60"))
+    process(C15(), "C15", setOf("I5", "I61", "I62", "I63", "I64", "I65", "I15", "I51", "I52", "I53", "I54", "I55", "I56", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70", "I10", "I20", "I30", "I40", "I50", "I21", "I22", "I23", "I24", "I25", "I26", "I27", "I28", "I29", "I30", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I60"))
+    process(C16(), "C16", setOf("I6", "I61", "I62", "I63", "I64", "I65", "I66", "I16", "I51", "I52", "I53", "I54", "I55", "I10", "I20", "I30", "I40", "I50", "I67", "I68", "I69", "I70", "I51", "I29", "I21", "I22", "I23", "I24", "I25", "I26", "I27", "I28", "I29", "I30", "I40", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I67", "I68", "I69", "I70"))
+    process(C17(), "C17", setOf("I7", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I17", "I51", "I52", "I53", "I54", "I10", "I68", "I69", "I70", "I20", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21", "I40"))
+    process(C18(), "C18", setOf("I8", "I18", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I51", "I52", "I53", "I10", "I69", "I70", "I20", "I30", "I29", "I28", "I27", "I26", "I25", "I24", "I23", "I22", "I21"))
+    process(C19(), "C19", setOf("I9", "I19", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I51", "I52", "I10", "I70", "I20"))
+    process(C20(), "C20", setOf("I10", "I20", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70", "I51"))
+
+    process(C21(), "C21", setOf("I31", "I32", "I33", "I40", "I37", "I33", "I36", "I34", "I35"))
+    process(C22(), "C22", setOf("I31", "I32", "I33", "I40", "I37", "I33", "I36", "I34", "I35"))
+    process(C23(), "C23", setOf("I37", "I38", "I39", "I33", "I36", "I34", "I35", "I32", "I31", "I40"))
+    process(C24(), "C24", setOf("I37", "I38", "I39", "I33", "I36", "I34", "I35", "I32", "I31", "I40", "I50", "I60", "I1", "I2", "I3", "I4", "I5", "I6", "I7", "I8", "I9", "I10", "I61", "I62", "I63", "I64", "I65", "I66", "I67", "I68", "I69", "I70"))
+    process(C25(), "C25", emptySet())
+
+    return "OK"
+}
diff --git a/js/js.translator/testData/box/expression/typeCheck/simpleIsInterface.kt b/js/js.translator/testData/box/expression/typeCheck/simpleIsInterface.kt
index 04ef8fe9680..fd19bd1da92 100644
--- a/js/js.translator/testData/box/expression/typeCheck/simpleIsInterface.kt
+++ b/js/js.translator/testData/box/expression/typeCheck/simpleIsInterface.kt
@@ -1,4 +1,5 @@
 // EXPECTED_REACHABLE_NODES: 1403
+
 package foo
 
 
diff --git a/libraries/stdlib/js-ir/runtime/BitMask.kt b/libraries/stdlib/js-ir/runtime/BitMask.kt
new file mode 100644
index 00000000000..43faba11b48
--- /dev/null
+++ b/libraries/stdlib/js-ir/runtime/BitMask.kt
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2010-2022 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 kotlin.js
+
+internal fun implement(vararg interfaces: dynamic): BitMask {
+    var maxSize = 1
+    val masks = js("[]")
+
+    for (i in interfaces) {
+        var currentSize = maxSize
+        val imask: BitMask? = i.prototype.`$imask$` ?: i.`$imask$`
+
+        if (imask != null) {
+            masks.push(imask)
+            currentSize = imask.intArray.size
+        }
+
+        val iid: Int? = i.`$metadata$`.iid
+        val iidImask: BitMask? = iid?.let { BitMask(arrayOf(it)) }
+
+        if (iidImask != null) {
+            masks.push(iidImask)
+            currentSize = JsMath.max(currentSize, iidImask.intArray.size)
+        }
+
+        if (currentSize > maxSize) {
+            maxSize = currentSize
+        }
+    }
+
+    val resultIntArray = IntArray(maxSize) { i ->
+        masks.reduce({ acc: Int, it: BitMask ->
+            if (i >= it.intArray.size)
+                acc
+            else
+                acc or it.intArray[i]
+        }, 0)
+    }
+
+    val result = BitMask(emptyArray())
+    result.intArray = resultIntArray
+    return result
+}
+
+internal class BitMask(activeBits: Array<Int>) {
+    var intArray: IntArray = run {
+        if (activeBits.size == 0) {
+            IntArray(0)
+        } else {
+            val max: Int = JsMath.asDynamic().max.apply(null, activeBits)
+            val intArray = IntArray((max shr 5) + 1)
+            for (activeBit in activeBits) {
+                val numberIndex = activeBit shr 5
+                val positionInNumber = activeBit and 31
+                val numberWithSettledBit = 1 shl positionInNumber
+                intArray[numberIndex] = intArray[numberIndex] or numberWithSettledBit
+            }
+            intArray
+        }
+    }
+
+    fun isBitSet(possibleActiveBit: Int): Boolean {
+        val numberIndex = possibleActiveBit shr 5
+        if (numberIndex > intArray.size) return false
+        val positionInNumber = possibleActiveBit and 31
+        val numberWithSettledBit = 1 shl positionInNumber
+        return intArray[numberIndex] and numberWithSettledBit != 0
+    }
+}
\ No newline at end of file
diff --git a/libraries/stdlib/js-ir/runtime/kotlinJsHacks.kt b/libraries/stdlib/js-ir/runtime/kotlinJsHacks.kt
index de82749f926..ac62314b184 100644
--- a/libraries/stdlib/js-ir/runtime/kotlinJsHacks.kt
+++ b/libraries/stdlib/js-ir/runtime/kotlinJsHacks.kt
@@ -5,6 +5,8 @@
 
 package kotlin.js
 
+import kotlin.reflect.KClass
+
 @PublishedApi
 internal fun <T : Enum<T>> enumValuesIntrinsic(): Array<T> =
     throw IllegalStateException("Should be replaced by compiler")
@@ -51,3 +53,6 @@ internal annotation class JsFun(val code: String)
  */
 @Target(AnnotationTarget.CLASS)
 internal annotation class JsImplicitExport()
+
+@Target(AnnotationTarget.CLASS)
+internal annotation class JsSubtypeCheckable(vararg val implements: KClass<*>)
\ No newline at end of file
diff --git a/libraries/stdlib/js-ir/runtime/reflectRuntime.kt b/libraries/stdlib/js-ir/runtime/reflectRuntime.kt
index 7d03a8904d4..a74d3b8b1cc 100644
--- a/libraries/stdlib/js-ir/runtime/reflectRuntime.kt
+++ b/libraries/stdlib/js-ir/runtime/reflectRuntime.kt
@@ -7,44 +7,45 @@ package kotlin.js
 
 import kotlin.reflect.KProperty
 
-internal fun getPropertyCallableRef(name: String, paramCount: Int, type: dynamic, getter: dynamic, setter: dynamic): KProperty<*> {
+internal fun getPropertyCallableRef(
+    name: String,
+    paramCount: Int,
+    superType: dynamic,
+    getter: dynamic,
+    setter: dynamic
+): KProperty<*> {
     getter.get = getter
     getter.set = setter
     getter.callableName = name
-    return getPropertyRefClass(getter, getKPropMetadata(paramCount, setter, type)).unsafeCast<KProperty<*>>()
+    return getPropertyRefClass(
+        getter,
+        getKPropMetadata(paramCount, setter),
+        getInterfaceMaskFor(getter, superType)
+    ).unsafeCast<KProperty<*>>()
 }
 
-internal fun getLocalDelegateReference(name: String, type: dynamic, mutable: Boolean, lambda: dynamic): KProperty<*> {
-    return getPropertyCallableRef(name, 0, type, lambda, if (mutable) lambda else null)
+internal fun getLocalDelegateReference(name: String, superType: dynamic, mutable: Boolean, lambda: dynamic): KProperty<*> {
+    return getPropertyCallableRef(name, 0, superType, lambda, if (mutable) lambda else null)
 }
 
-private fun getPropertyRefClass(obj: Ctor, metadata: Metadata): dynamic {
-    obj.`$metadata$` = metadata;
-    obj.constructor = obj;
+private fun getPropertyRefClass(obj: Ctor, metadata: Metadata, imask: BitMask): dynamic {
+    obj.`$metadata$` = metadata
+    obj.constructor = obj
+    obj.`$imask$` = imask
     return obj;
 }
 
-private fun getKPropMetadata(paramCount: Int, setter: Any?, type: dynamic): dynamic {
-    val mdata: Metadata = propertyRefClassMetadataCache[paramCount][if (setter == null) 0 else 1]
+private fun getInterfaceMaskFor(obj: Ctor, superType: dynamic): BitMask =
+    obj.`$imask$` ?: implement(superType)
 
-    if (mdata.interfaces.size == 0) {
-        mdata.interfaces.asDynamic().push(type)
-
-        if (mdata.interfacesCache == null) {
-            mdata.interfacesCache = generateInterfaceCache()
-        } else {
-            mdata.interfacesCache!!.isComplete = false
-        }
-
-        mdata.interfacesCache!!.extendCacheWithSingle(type)
-    }
-
-    return mdata
+@Suppress("UNUSED_PARAMETER")
+private fun getKPropMetadata(paramCount: Int, setter: Any?): dynamic {
+    return propertyRefClassMetadataCache[paramCount][if (setter == null) 0 else 1]
 }
 
 private fun metadataObject(): Metadata {
     val undef = js("undefined")
-    return classMeta(undef, undef, undef, undef, undef, undef)
+    return classMeta(undef, undef, undef, undef)
 }
 
 private val propertyRefClassMetadataCache: Array<Array<dynamic>> = arrayOf<Array<dynamic>>(
diff --git a/libraries/stdlib/js-ir/runtime/typeCheckUtils.kt b/libraries/stdlib/js-ir/runtime/typeCheckUtils.kt
index c15e4aaa23d..01695a315e1 100644
--- a/libraries/stdlib/js-ir/runtime/typeCheckUtils.kt
+++ b/libraries/stdlib/js-ir/runtime/typeCheckUtils.kt
@@ -5,36 +5,42 @@
 
 package kotlin.js
 
-internal fun interfaceMeta(
+internal fun setMetadataFor(
+    ctor: Ctor,
     name: String?,
-    interfaces: Array<Ctor>?,
+    metadataConstructor: (name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?) -> Metadata,
+    parent: Ctor?,
+    interfaces: Array<dynamic>?,
     associatedObjectKey: Number?,
     associatedObjects: dynamic,
-    suspendArity: Array<Int>?,
-): Metadata {
-    return createMetadata("interface", name, interfaces, associatedObjectKey, associatedObjects, suspendArity, js("undefined"))
+    suspendArity: Array<Int>?
+) {
+    if (parent != null) {
+        js("""
+          ctor.prototype = Object.create(parent.prototype)
+          ctor.prototype.constructor = ctor;
+        """)
+    }
+
+    val metadata = metadataConstructor(name, associatedObjectKey, associatedObjects, suspendArity)
+    ctor.`$metadata$` = metadata
+
+    if (interfaces != null) {
+        val receiver = if (metadata.iid != null) ctor else ctor.prototype
+        receiver.`$imask$` = implement(*interfaces)
+    }
 }
 
-internal fun objectMeta(
-    name: String?,
-    interfaces: Array<Ctor>?,
-    associatedObjectKey: Number?,
-    associatedObjects: dynamic,
-    suspendArity: Array<Int>?,
-    fastPrototype: Prototype?,
-): Metadata {
-    return createMetadata("object", name, interfaces, associatedObjectKey, associatedObjects, suspendArity, fastPrototype)
+internal fun interfaceMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
+    return createMetadata("interface", name, associatedObjectKey, associatedObjects, suspendArity, generateInterfaceId())
 }
 
-internal fun classMeta(
-    name: String?,
-    interfaces: Array<Ctor>?,
-    associatedObjectKey: Number?,
-    associatedObjects: dynamic,
-    suspendArity: Array<Int>?,
-    fastPrototype: Prototype?,
-): Metadata {
-    return createMetadata("class", name, interfaces, associatedObjectKey, associatedObjects, suspendArity, fastPrototype)
+internal fun objectMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
+    return createMetadata("object", name, associatedObjectKey, associatedObjects, suspendArity, null)
+}
+
+internal fun classMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
+    return createMetadata("class", name, associatedObjectKey, associatedObjects, suspendArity, null)
 }
 
 // Seems like we need to disable this check if variables are used inside js annotation
@@ -42,192 +48,103 @@ internal fun classMeta(
 private fun createMetadata(
     kind: String,
     name: String?,
-    interfaces: Array<Ctor>?,
     associatedObjectKey: Number?,
     associatedObjects: dynamic,
     suspendArity: Array<Int>?,
-    fastPrototype: Prototype?
+    iid: Int?
 ): Metadata {
     return js("""({
     kind: kind,
     simpleName: name,
-    interfaceId: kind === "interface" ? -1 : undefined,
-    interfaces: interfaces || [],
     associatedObjectKey: associatedObjectKey,
     associatedObjects: associatedObjects,
     suspendArity: suspendArity,
-    fastPrototype: fastPrototype,
     ${'$'}kClass$: undefined,
-    interfacesCache: {
-       isComplete: fastPrototype === undefined && (interfaces === undefined || interfaces.length === 0),
-       implementInterfaceMemo: {}
-    }
+    iid: iid
 })""")
 }
 
 internal external interface Metadata {
     val kind: String
-    val interfaces: Array<Ctor>
     // This field gives fast access to the prototype of metadata owner (Object.getPrototypeOf())
     // Can be pre-initialized or lazy initialized and then should be immutable
     val simpleName: String?
     val associatedObjectKey: Number?
     val associatedObjects: dynamic
-    var interfaceId: Number?
-    var fastPrototype: Prototype?
     val suspendArity: Array<Int>?
+    val iid: Int?
 
     var `$kClass$`: dynamic
-    // This is an object for memoization of a isInterfaceImpl function
-    // Can be mutated quite often
-    var interfacesCache: IsImplementsCache?
-}
-
-// This is a flag for memoization of a isInterfaceImpl function
-internal external interface IsImplementsCache {
-    var isComplete: Boolean
-    val implementInterfaceMemo: dynamic
 }
 
 internal external interface Ctor {
-    var `$metadata$`: Metadata?
+    var `$imask$`: BitMask?
+    var `$metadata$`: Metadata
     var constructor: Ctor?
-    val prototype: Prototype?
+    val prototype: dynamic
 }
 
-internal external interface Prototype {
-    val constructor: Ctor?
-}
+private var iid: Int? = null
 
-private var interfacesCounter = 0
-
-private fun Ctor.getOrDefineInterfaceId(): Number? {
-    val metadata = `$metadata$`.unsafeCast<Metadata>()
-    val interfaceId = metadata.interfaceId ?: -1
-    return if (interfaceId != -1) {
-        interfaceId
+@Suppress("SMARTCAST_IMPOSSIBLE")
+internal fun generateInterfaceId(): Int {
+    if (iid == null) {
+        iid = 1
     } else {
-        val result = interfacesCounter++
-        metadata.interfaceId = result
-        result
-    }
-}
-
-private fun Ctor.getPrototype() = prototype?.let { js("Object").getPrototypeOf(it).unsafeCast<Prototype>() }
-
-internal fun IsImplementsCache.extendCacheWith(cache: IsImplementsCache?) {
-    val anotherInterfaceMemo = cache?.implementInterfaceMemo ?: return
-    js("Object").assign(implementInterfaceMemo, anotherInterfaceMemo)
-}
-
-internal fun IsImplementsCache.extendCacheWithSingle(intr: Ctor) {
-    implementInterfaceMemo[intr.getOrDefineInterfaceId()] = true
-}
-
-private fun fastGetPrototype(ctor: Ctor): Prototype? {
-    return ctor.`$metadata$`?.run {
-        if (fastPrototype == null) {
-            fastPrototype = ctor.getPrototype()
-        }
-        fastPrototype
-    } ?: ctor.getPrototype()
-}
-
-private fun completeInterfaceCache(ctor: Ctor): IsImplementsCache? {
-    val metadata = ctor.`$metadata$`
-
-    if (metadata != null && metadata.interfacesCache == null)  {
-        metadata.interfacesCache = generateInterfaceCache()
+        iid += 1
     }
 
-    val interfacesCache = metadata?.interfacesCache
-
-    if (interfacesCache != null) {
-        if (interfacesCache.isComplete == true) {
-            return interfacesCache
-        }
-
-        for (i in metadata.interfaces) {
-            interfacesCache.extendCacheWithSingle(i)
-            interfacesCache.extendCacheWith(completeInterfaceCache(i))
-        }
-    }
-
-    val parentInterfacesCache = fastGetPrototype(ctor)?.constructor?.let(::completeInterfaceCache)
-
-    return interfacesCache?.apply {
-        extendCacheWith(parentInterfacesCache)
-        isComplete = true
-    } ?: parentInterfacesCache
+    return iid
 }
 
-// Old JS Backend
-internal fun generateInterfaceCache(): IsImplementsCache {
-   return js("{ isComplete: false, implementInterfaceMemo: {} }")
+@Suppress("UNUSED_PARAMETER")
+private fun getPrototypeOf(obj: dynamic) =
+    js("Object.getPrototypeOf(obj)")
+
+private fun searchForMetadata(obj: dynamic): Metadata? {
+    if (obj == null) {
+        return null
+    }
+    var metadata: Metadata? = obj.`$metadata$`
+    var currentObject = getPrototypeOf(obj)
+
+    while (metadata == null && currentObject != null) {
+        val currentConstructor = currentObject.constructor
+        metadata = currentConstructor.`$metadata$`
+        currentObject = getPrototypeOf(currentObject)
+    }
+
+    return metadata
 }
 
-private fun isInterfaceImpl(ctor: Ctor, iface: Ctor): Boolean {
-    if (ctor === iface) {
-        return true
+// TODO: Remove after 1.8 bootstrapping
+// Needed to pass all nodejs tests, because of stdlib compilation via bootstrapped compiler with old metadata format
+private fun verySlowIsInterfaceImpl(obj: dynamic, iface: dynamic): Boolean {
+    val metadata = searchForMetadata(obj) ?: return false
+    val interfaces = metadata.asDynamic().associatedObjectKey
+
+    if (
+        interfaces != null &&
+        (interfaces.indexOf(iface) != -1 || interfaces.some { x -> verySlowIsInterfaceImpl(x, iface) })
+    ) {
+       return true
     }
 
-    val metadata = ctor.`$metadata$`
+    return verySlowIsInterfaceImpl(getPrototypeOf(obj), iface)
+}
 
-    if (metadata != null && metadata.interfacesCache == null)  {
-        metadata.interfacesCache = generateInterfaceCache()
-    }
-
-    val interfacesCache = metadata?.interfacesCache
-
-    return if (interfacesCache != null) {
-        if (!interfacesCache.isComplete) completeInterfaceCache(ctor)
-        val interfaceId = iface.`$metadata$`?.interfaceId ?: return false
-        !!interfacesCache.implementInterfaceMemo[interfaceId]
-    } else {
-        val constructor = fastGetPrototype(ctor)?.constructor ?: return false
-        isInterfaceImpl(constructor, iface)
-    }
+private fun isInterfaceImpl(obj: dynamic, iface: Int): Boolean {
+    val mask: BitMask = obj.`$imask$`.unsafeCast<BitMask?>() ?: return false
+    return mask.isBitSet(iface)
 }
 
 internal fun isInterface(obj: dynamic, iface: dynamic): Boolean {
-    val ctor = obj.constructor ?: return false
-    return isInterfaceImpl(ctor, iface)
-}
-
-/*
-
-internal interface ClassMetadata {
-    val simpleName: String
-    val interfaces: Array<dynamic>
-}
-
-// TODO: replace `isInterface` with the following
-public fun isInterface(ctor: dynamic, IType: dynamic): Boolean {
-    if (ctor === IType) return true
-
-    val metadata = ctor.`$metadata$`.unsafeCast<ClassMetadata?>()
-
-    if (metadata !== null) {
-        val interfaces = metadata.interfaces
-        for (i in interfaces) {
-            if (isInterface(i, IType)) {
-                return true
-            }
-        }
+    return if (obj.`$imask$` != null) {
+        isInterfaceImpl(obj, iface.`$metadata$`.iid)
+    } else {
+        verySlowIsInterfaceImpl(obj, iface)
     }
-
-    var superPrototype = ctor.prototype
-    if (superPrototype !== null) {
-        superPrototype = js("Object.getPrototypeOf(superPrototype)")
-    }
-
-    val superConstructor = if (superPrototype !== null) {
-        superPrototype.constructor
-    } else null
-
-    return superConstructor != null && isInterface(superConstructor, IType)
 }
-*/
 
 internal fun isSuspendFunction(obj: dynamic, arity: Int): Boolean {
     if (jsTypeOf(obj) == "function") {
@@ -237,7 +154,7 @@ internal fun isSuspendFunction(obj: dynamic, arity: Int): Boolean {
 
     if (jsTypeOf(obj) == "object" && jsIn("${'$'}metadata${'$'}", obj.constructor)) {
         @Suppress("IMPLICIT_BOXING_IN_IDENTITY_EQUALS")
-        return obj.constructor.unsafeCast<Ctor>().`$metadata$`?.suspendArity?.let {
+        return obj.constructor.unsafeCast<Ctor>().`$metadata$`.suspendArity?.let {
             var result = false
             for (item in it) {
                 if (arity == item) {
@@ -288,7 +205,6 @@ internal fun isFloatArray(a: dynamic): Boolean = jsInstanceOf(a, js("Float32Arra
 internal fun isDoubleArray(a: dynamic): Boolean = jsInstanceOf(a, js("Float64Array"))
 internal fun isLongArray(a: dynamic): Boolean = isJsArray(a) && a.`$type$` === "LongArray"
 
-
 internal fun jsGetPrototypeOf(jsClass: dynamic) = js("Object").getPrototypeOf(jsClass)
 
 internal fun jsIsType(obj: dynamic, jsClass: dynamic): Boolean {
@@ -320,8 +236,9 @@ internal fun jsIsType(obj: dynamic, jsClass: dynamic): Boolean {
         return jsInstanceOf(obj, jsClass)
     }
 
-    if (klassMetadata.kind === "interface" && obj.constructor != null) {
-        return isInterfaceImpl(obj.constructor, jsClass)
+    if (klassMetadata.kind === "interface") {
+        val iid =  klassMetadata.iid.unsafeCast<Int?>()
+        return iid?.let { isInterfaceImpl(obj, it) } ?: verySlowIsInterfaceImpl(obj, constructor)
     }
 
     return false
@@ -329,14 +246,16 @@ internal fun jsIsType(obj: dynamic, jsClass: dynamic): Boolean {
 
 internal fun isNumber(a: dynamic) = jsTypeOf(a) == "number" || a is Long
 
+@OptIn(JsIntrinsic::class)
 internal fun isComparable(value: dynamic): Boolean {
     var type = jsTypeOf(value)
 
     return type == "string" ||
             type == "boolean" ||
             isNumber(value) ||
-            isInterface(value, Comparable::class.js)
+            isInterface(value, jsClassIntrinsic<Comparable<*>>())
 }
 
+@OptIn(JsIntrinsic::class)
 internal fun isCharSequence(value: dynamic): Boolean =
-    jsTypeOf(value) == "string" || isInterface(value, CharSequence::class.js)
+    jsTypeOf(value) == "string" || isInterface(value, jsClassIntrinsic<CharSequence>())
diff --git a/libraries/stdlib/js-ir/src/kotlin/reflection_js-ir.kt b/libraries/stdlib/js-ir/src/kotlin/reflection_js-ir.kt
index 0a489de3f41..755133ea89c 100644
--- a/libraries/stdlib/js-ir/src/kotlin/reflection_js-ir.kt
+++ b/libraries/stdlib/js-ir/src/kotlin/reflection_js-ir.kt
@@ -9,8 +9,8 @@ import kotlin.reflect.js.internal.*
 @PublishedApi
 internal fun <T : Annotation> KClass<*>.findAssociatedObject(annotationClass: KClass<T>): Any? {
     return if (this is KClassImpl<*> && annotationClass is KClassImpl<T>) {
-        val key = annotationClass.jClass.asDynamic().unsafeCast<Ctor>().`$metadata$`?.associatedObjectKey?.unsafeCast<Int>() ?: return null
-        val map = jClass.asDynamic().unsafeCast<Ctor>().`$metadata$`?.associatedObjects ?: return null
+        val key = annotationClass.jClass.asDynamic().`$metadata$`?.associatedObjectKey?.unsafeCast<Int>() ?: return null
+        val map = jClass.asDynamic().`$metadata$`?.associatedObjects ?: return null
         val factory = map[key] ?: return null
         return factory()
     } else {