test.re

type fieldType = 
  | Numeric
  | Alphanumeric
  | Alpha;

type fieldData('a) = {
    name: string,
    width: int,
    position: int,
    value: option('a),
    fieldType: fieldType
};

let recordTypeCode = {
    name: "Record Type Code",
    width: 1,
    position: 1,
    fieldType: Numeric,
    value: Some("6"),
};

type fields = {
    recordTypeCode: RequiredField(recordTypeCode)
};