src/language-js/printer-estree.js/printMethodInternal
function printMethodInternal(path, options, print) {
  const parts = [
    printFunctionTypeParameters(path, options, print),
    group(
      concat([
        printFunctionParams(path, print, options),
        printReturnType(path, print, options),
      ])
    ),
  ];

  if (path.getNode().body) {
    parts.push(" ", path.call(print, "body"));
  } else {
    parts.push(options.semi ? ";" : "");
  }

  return concat(parts);
}