getParameterElement method

Implementation

ParameterElement getParameterElement() {
  final parameters = _methodElement.parameters;
  if (parameters.isEmpty) {
    throw InvalidGenerationSourceError(
      'There is no parameter supplied for this method. Please add one.',
      element: _methodElement,
    );
  } else if (parameters.length > 1) {
    throw InvalidGenerationSourceError(
      'Only one parameter is allowed on this.',
      element: _methodElement,
    );
  }
  return parameters.first;
}