@Override
	public ProgramLocation getProgramLocation(int row, int col, ListingField bf) {
		ProxyObj<?> proxy = bf.getProxy();
		if (proxy instanceof FunctionProxy) {
			FunctionProxy functionProxy = (FunctionProxy) proxy;
			Function function = functionProxy.getObject();
			return new FunctionTagFieldLocation(function.getProgram(),
				functionProxy.getLocationAddress(), functionProxy.getFunctionAddress(),
				function.getCallFixup(), col);
		}
		return null;
	}
Overridden to ensure that we return` a {@link FunctionTagFieldLocation} instance.
Ghidra/Features/Base/src/main/java/ghidra/app/util/viewer/field/FunctionTagFieldFactory.java