function _getTarget(source) {
  const {chart, fill, line} = source;

  if (isFinite(fill)) {
    return getLineByIndex(chart, fill);
  }

  if (fill === 'stack') {
    return _buildStackLine(source);
  }

  if (fill === 'shape') {
    return true;
  }

  const boundary = computeBoundary(source);

  if (boundary instanceof simpleArc) {
    return boundary;
  }

  return _createBoundaryLine(boundary, line);
}
@typedef { import('../../core/core.controller.js').default } Chart
@typedef { import('../../core/core.scale.js').default } Scale
@typedef { import('../../elements/element.point.js').default } PointElement