public void add(Declaration dec) throws IllegalArgumentException {
		if (dec == null || dec.getDataType() == null) {
			return;
		}
		// not a bitfield, just add the data type to composite
		if (!dec.isBitField()) {
			parent.add(dec.getDataType(), dec.getName(), dec.getComment());
			return;
		}

		// add bit-field component
		DataType dataType = dec.getDataType();
		try {
			parent.addBitField(dataType, dec.getBitFieldSize(), dec.getName(), dec.getComment());
		}
		catch (InvalidDataTypeException e) {
			// TODO Auto-generated catch block
			throw new IllegalArgumentException(
				"Invalid bitfield " + dec.getName() + " : " + dec.getBitFieldSize());
		}
	}
Used by the CParser to handle fields added to structures(composites).
Currently only bitfields are handled specially.

NOTE: when bitfield handling is added directly to structures, this class may
no longer be necessary.
Ghidra/Features/Base/src/main/java/ghidra/app/util/cparser/C/CompositeHandler.java