You might want to filter out `null` and `NoSymbol`?

`referenced` is used to link to related symbols, for instance a getter references the field value, a lazy accessor references the field where it's stored... there may be other cases, the only way to know for sure is to check the compiler sources :). AFAIK, `referenced` can't be read directly, but instead has more meaningful getters (like `lazyAccessor`).