message: Printer case for Flow BigIntLiteralTypeAnnotation.
  Apparently n.value is always null, and n.raw is what matters.
diff: @@ -1712,6 +1712,9 @@ function genericPrintNoParens(path: any, options: any, print: any) {
  assert.strictEqual(typeof n.value, "number");
  return fromString(JSON.stringify(n.value), options);
  + case "BigIntLiteralTypeAnnotation":
  + return fromString(n.raw, options);
  +
  case "StringTypeAnnotation":
  return fromString("string", options);
  