The follow type of rule causes the ocaml printer to crash
test. A ::= "{{" Id "}" "}" ; -- Note: should be "}}"

The error message is Fatal error: exception Invalid_argument("Bytes.create")

I have traced this to the indent function let indent (i: int) : string = "\n" ^ String.make i ' ' and I think that changed to let indent (i: int) : string = if i > 0 then "\n" ^ String.make i ' ' else "\n" ;; to match the behavior of other backends.