UFile (package = )
    UClass (name = ReceiverFunKt)
        UAnnotationMethod (name = foo)
            UParameter (name = $receiver)
                UAnnotation (fqName = MyReceiverAnnotation)
                UAnnotation (fqName = org.jetbrains.annotations.NotNull)
            UBlockExpression
                UReturnExpression
                    UQualifiedReferenceExpression
                        UThisExpression (label = null)
                        USimpleNameReferenceExpression (identifier = length)
    UClass (name = MyReceiverAnnotation)