[K/JS] Add ability to use is checks on external objects

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

@@ -95,6 +95,7 @@ class JsIntrinsics(private val irBuiltIns: IrBuiltIns, val context: JsIrBackendC
 
     val jsInstanceOf = getInternalFunction("jsInstanceOfIntrinsic")
     val jsTypeOf = getInternalFunction("jsTypeOf")
+    val isExternalObject = getInternalFunction("isExternalObject")
 
     // Number conversions:
 

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

@@ -53,6 +53,7 @@ class TypeOperatorLowering(val context: JsIrBackendContext) : BodyLoweringPass {
     private val isObjectSymbol get() = context.intrinsics.isObjectSymbol
 
     private val instanceOfIntrinsicSymbol = context.intrinsics.jsInstanceOf
+    private val isExternalObjectSymbol = context.intrinsics.isExternalObject
     private val typeOfIntrinsicSymbol = context.intrinsics.jsTypeOf
     private val jsClassIntrinsicSymbol = context.intrinsics.jsClass
 
@@ -270,6 +271,7 @@ class TypeOperatorLowering(val context: JsIrBackendContext) : BodyLoweringPass {
                             generateInterfaceCheck(argument, toType)
                         }
                     }
+                    toType.isExternalObject() -> generateIsExternalObject(argument, toType)
                     else -> generateNativeInstanceOf(argument, toType)
                 }
             }
@@ -360,6 +362,14 @@ class TypeOperatorLowering(val context: JsIrBackendContext) : BodyLoweringPass {
                 }
             }
 
+            private fun generateIsExternalObject(argument: IrExpression, toType: IrType): IrExpression {
+                val irType = wrapTypeReference(toType)
+                return JsIrBuilder.buildCall(isExternalObjectSymbol).apply {
+                    putValueArgument(0, argument)
+                    putValueArgument(1, irType)
+                }
+            }
+
             private fun generateNativeInstanceOf(argument: IrExpression, toType: IrType): IrExpression {
                 val irType = wrapTypeReference(toType)
                 return JsIrBuilder.buildCall(instanceOfIntrinsicSymbol).apply {

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrTypeUtils.kt

@@ -57,6 +57,8 @@ fun IrType.isTypeParameter() = classifierOrNull is IrTypeParameterSymbol
 
 fun IrType.isInterface() = classOrNull?.owner?.kind == ClassKind.INTERFACE
 
+fun IrType.isExternalObject() = classOrNull?.owner.let { it?.kind == ClassKind.OBJECT && it.isExternal }
+
 fun IrType.isAnnotation() = classOrNull?.owner?.kind == ClassKind.ANNOTATION_CLASS
 
 fun IrType.isFunctionOrKFunction() = isFunction() || isKFunction()