src/language-js/printer-estree.js/getLeftSide
function getLeftSide(node) {
  if (node.expressions) {
    return node.expressions[0];
  }
  return (
    node.left ||
    node.test ||
    node.callee ||
    node.object ||
    node.tag ||
    node.argument ||
    node.expression
  );
}