When there is a component and an instance which both have the same id, the "built-in" QML Code model incorrectly classifies both of these ids as instance ids and displays a "Duplicate Id. (M15)" error in the editor.
The error does not occur when qmllint is run nor when the QML Language Server is turned on, since it correctly identifies that the component id is not an instance id.

import QtQuick

Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")

component MyComponent : Item {
id: myComponent
Item {
anchors.fill: myComponent
}
}

MyComponent {
id: myComponent
}