pub fn default_field(
  field: a,
  default: b,
  decoder: decode.Decoder(b),
  then: fn(b) -> decode.Decoder(c),
) -> decode.Decoder(c)

pub fn discriminate(
  field: name,
  decoder: decode.Decoder(d),
  default: t,
  choose: fn(d) -> Result(decode.Decoder(t), String),
) -> decode.Decoder(t)

pub fn optional_field(
  field: a,
  decoder: decode.Decoder(b),
  then: fn(option.Option(b)) -> decode.Decoder(c),
) -> decode.Decoder(c)

pub fn sparse(entries: List(#(String, json.Json))) -> json.Json