Json_codec.Builtin_codecsval unit : builtin_codecval bool : builtin_codecval int : builtin_codecval int53p : builtin_codecval float : builtin_codecval string : builtin_codecval uchar : builtin_codecval byte : builtin_codecval bytes : builtin_codecval option : builtin_codecval list : builtin_codecval uninhabitable : builtin_codecval map : builtin_codecval all : (string * builtin_codec) list