In Google Apps Script, how do you get the Range of the calling cell in a custom function?

I'm trying to get a reference to the calling cell's range in a Google Sheets custom function.

For example:

function MyAddress() {
    callingRange = // get calling cell reference here
    return callingRange.getA1Notation();
}

getActiveCell() isn't guaranteed to work because calculation doesn't necessarily occur while the calling cell is active (I could be wrong about this, but can't find confirmation). Any suggestions?