Signal and Property are rather different properties at this point, however they are weirdly mixed up in UiPublicMember.

Instead of variant/union, the UiPublicMember somehow considered Signal by default, while at the same time duplicating multiple UiPropertyAttributes methods on its API, introducing quite some copy-paste.

The naming there is also rather confusing, for example 

union {
        SourceLocation m_propertyToken = SourceLocation {};
        UiPropertyAttributes *m_attributes;
    };

Which means that UiPropertyAttributes also contains a location of "propery" keyword/token, but m_propertyToken actually means token of the "signal" keyword

Additionally there could probably be better handling of property attributes themselves, instead of multiple same `if` conditions and warnings in the parser

Some ideas for better separation of concerns https://codereview.qt-project.org/c/qt/qtdeclarative/+/656089