public TextBuffer popNewlineGroup() {
    if (myCurrentGroup == myRootGroup) {
      throw new IllegalStateException("Cannot pop root group: " + this.convertToStringAndAllowDataDiscard());
    }
    assert myStringBuilder.length() >= myCurrentGroup.myStart;
    myCurrentGroup.myLength = myStringBuilder.length() - myCurrentGroup.myStart;
    myCurrentGroup = myCurrentGroup.myParent;
    return this;
  }
If the current group is applied, add a newline here. Otherwise, add the argument.
If {@code dedent} is true, the extra indent from this group is unapplied from this point on.
src/org/jetbrains/java/decompiler/util/TextBuffer.java