QML Optimizer causes boolean property to be inverted

With QML_DISABLE_OPTIMIZER enabled this code works just as expected:

property bool canCopy: editor && editor.selectedText != "" && (editor.echoMode == null || editor.echoMode == TextInput.Normal)
property bool canCut: internal.canCopy && !editor.readOnly

But with QML_DISABLE_OPTIMIZER disabled (the default) the last half of the
second line somehow permanently inverts the value of the property in the
first half of that expression. E.g. "&& !editor.readOnly" inverts the value
assigned to the canCopy property.