code: function validateEat(subvalue) {
        /* istanbul ignore if */
        if (value.substring(0, subvalue.length) !== subvalue) {
          // Capture stack-trace.
          self.file.fail(
            new Error(
              'Incorrectly eaten value: please report this warning on https://git.io/vg5Ft'
            ),
            now()
          )
        }
      }
docs: Throw when a value is incorrectly eaten.  This shouldn’t happen but will throw on new, incorrect rules.