Attached property must be attached to an object deriving from a particular type

What happened?

You instantiated an attached property in an object of the wrong type.

Why is this bad?

The attached property will not work.

Example

import QtQuick

Item {
    QtObject {
        LayoutMirroring.enabled: true
    }
}

To fix this warning, change the enclosing type to inherit from the type mentioned in the warning message:

import QtQuick

Item {
    Item {
        LayoutMirroring.enabled: true
    }
}