When we have a type with an ocaml representation of int64, it doesn't get serialized in the same way as it would in ocaml atdgen-runtime.
ex:
type int64 = int <ocaml repr="int64">
In this example, the value would be returned from the ocaml side as an int in the json response, and the atdgen-codec-runtime would complain that it can't parse that value as it's expecting a string.
Int64 serialization functions:
ocaml atdgen-runtime:
let write_int64 ob x =
Bi_outbuf.add_string ob (Int64.to_string x)
bs-atdgen-codec-runtime:
let int64 s = string (Int64.to_string s)