lib.types.listOf

The following is the current implementation of this function.

elemType:
    mkOptionType rec {
      name = "listOf";
      description = "list of ${
        optionDescriptionPhrase (class: class == "noun" || class == "composite") elemType
      }";
      descriptionClass = "composite";
      check = {
        __functor = _self: isList;
        isV2MergeCoherent = true;
      };
      merge = {
        __functor =
          self: loc: defs:
          (self.v2 { inherit loc defs; }).value;
        v2 =
          { loc, defs }:
          let
            evals = filter (x: x.optionalValue ? value) (
              concatLists (
                imap1 (
                  n: def:
                  imap1 (
                    m: def':
                    (mergeDefinitions (loc ++ [ "[definition ${toString n}-entry ${toString m}]" ]) elemType [
                      {
                        inherit (def) file;
                        value = def';
                      }
                    ])
                  ) def.value
                ) defs
              )
            );
          in
          {
            headError = checkDefsForError check loc defs;
            value = map (x: x.optionalValue.value or x.mergedValue) evals;
            valueMeta.list = map (v: v.checkedAndMerged.valueMeta) evals;
          };
      };
      emptyValue = {
        value = [ ];
      };
      getSubOptions = prefix: elemType.getSubOptions (prefix ++ [ "*" ]);
      getSubModules = elemType.getSubModules;
      substSubModules = m: listOf (elemType.substSubModules m);
      functor = (elemTypeFunctor name { inherit elemType; }) // {
        type = payload: lib.types.listOf payload.elemType;
      };
      nestedTypes.elemType = elemType;
    }