lib.types.either

The following is the current implementation of this function.

either =
        t1: t2:
        mkOptionType rec {
          name = "either";
          description =
            if t1.descriptionClass or null == "nonRestrictiveClause" then
              # Plain, but add comma
              "${t1.description}, or ${
                optionDescriptionPhrase (class: class == "noun" || class == "conjunction") t2
              }"
            else
              "${optionDescriptionPhrase (class: class == "noun" || class == "conjunction") t1} or ${
                optionDescriptionPhrase (
                  class: class == "noun" || class == "conjunction" || class == "composite"
                ) t2
              }";
          descriptionClass = "conjunction";
          check = x: t1.check x || t2.check x;
          merge =
            loc: defs:
            let
              defList = map (d: d.value) defs;
            in
            if all (x: t1.check x) defList then
              t1.merge loc defs
            else if all (x: t2.check x) defList then
              t2.merge loc defs
            else
              mergeOneOption loc defs;
          typeMerge =
            f':
            let
              mt1 = t1.typeMerge (elemAt f'.payload.elemType 0).functor;
              mt2 = t2.typeMerge (elemAt f'.payload.elemType 1).functor;
            in
            if (name == f'.name) && (mt1 != null) && (mt2 != null) then functor.type mt1 mt2 else null;
          functor = elemTypeFunctor name {
            elemType = [
              t1
              t2
            ];
          };
          nestedTypes.left = t1;
          nestedTypes.right = t2;
        };