src/language-js/print/assignment.js/printAssignmentExpression
function printAssignmentExpression(path, options, print) {
  const n = path.getValue();
  return printAssignment(
    n.left,
    path.call(print, "left"),
    concat([" ", n.operator]),
    n.right,
    path.call(print, "right"),
    options
  );
}