src/doc/doc-debug.js/printDoc
function printDoc(doc) {
  if (typeof doc === "string") {
    return JSON.stringify(doc);
  }

  if (doc.type === "line") {
    if (doc.literalline) {
      return "literalline";
    }
    if (doc.hard) {
      return "hardline";
    }
    if (doc.soft) {
      return "softline";
    }
    return "line";
  }

  if (doc.type === "break-parent") {
    return "breakParent";
  }

  if (doc.type === "concat") {
    return "[" + doc.parts.map(printDoc).join(", ") + "]";
  }

  if (doc.type === "indent") {
    return "indent(" + printDoc(doc.contents) + ")";
  }

  if (doc.type === "align") {
    return doc.n === -Infinity
      ? "dedentToRoot(" + printDoc(doc.contents) + ")"
      : doc.n < 0
        ? "dedent(" + printDoc(doc.contents) + ")"
        : doc.n.type === "root"
          ? "markAsRoot(" + printDoc(doc.contents) + ")"
          : "align(" +
            JSON.stringify(doc.n) +
            ", " +
            printDoc(doc.contents) +
            ")";
  }

  if (doc.type === "if-break") {
    return (
      "ifBreak(" +
      printDoc(doc.breakContents) +
      (doc.flatContents ? ", " + printDoc(doc.flatContents) : "") +
      ")"
    );
  }

  if (doc.type === "group") {
    if (doc.expandedStates) {
      return (
        "conditionalGroup(" +
        "[" +
        doc.expandedStates.map(printDoc).join(",") +
        "])"
      );
    }

    return (
      (doc.break ? "wrappedGroup" : "group") +
      "(" +
      printDoc(doc.contents) +
      ")"
    );
  }

  if (doc.type === "fill") {
    return "fill" + "(" + doc.parts.map(printDoc).join(", ") + ")";
  }

  if (doc.type === "line-suffix") {
    return "lineSuffix(" + printDoc(doc.contents) + ")";
  }

  if (doc.type === "line-suffix-boundary") {
    return "lineSuffixBoundary";
  }

  throw new Error("Unknown doc type " + doc.type);
}