lib/types: add 'checkDefsForError' utility for checking defs with a given check

      }is accessed, use `${lib.optionalString (loc != null) "type."}nestedTypes.elemType` instead.

    '' payload.elemType;

  checkDefsForError =

    check: loc: defs:

    let

      invalidDefs = filter (def: !check def.value) defs;

    in

    if invalidDefs != [ ] then "Definition values: ${showDefs invalidDefs}" else null;

  outer_types = rec {

    isType = type: x: (x._type or "") == type;