Temporal with Zod + tRPC

temporal.ts

import { Temporal } from "@js-temporal/polyfill"
import { z } from "zod"

/*
  "Zod extras", use like z.
  
   date: zx.instant()
*/

export const zx = {
  instant: () =>
    z
      .instanceof(Temporal.Instant)
      .refine((v) => attempt(() => Temporal.Instant.from(v)))
      .transform((v) => Temporal.Instant.from(v)),

  zonedDateTime: () =>
    z
      .instanceof(Temporal.ZonedDateTime)
      .refine((v) => attempt(() => Temporal.ZonedDateTime.from(v)))
      .transform((v) => Temporal.ZonedDateTime.from(v)),

  plainDate: () =>
    z
      .instanceof(Temporal.PlainDate)
      .refine((v) => attempt(() => Temporal.PlainDate.from(v)))
      .transform((v) => Temporal.PlainDate.from(v)),
 }
 
/*
  For use with tRPC after setting up superjson as a transforner
*/

import superjson from "superjson"

superjson.registerCustom<Temporal.Instant, string>(
  {
    isApplicable: (v): v is Temporal.Instant => v instanceof Temporal.Instant,
    serialize: (v) => v.toJSON(),
    deserialize: (v) => Temporal.Instant.from(v),
  },
  "Temporal.Instant"
)

superjson.registerCustom<Temporal.ZonedDateTime, string>(
  {
    isApplicable: (v): v is Temporal.ZonedDateTime => v instanceof Temporal.ZonedDateTime,
    serialize: (v) => v.toJSON(),
    deserialize: (v) => Temporal.ZonedDateTime.from(v),
  },
  "Temporal.ZonedDateTime"
)

superjson.registerCustom<Temporal.PlainDate, string>(
  {
    isApplicable: (v): v is Temporal.PlainDate => v instanceof Temporal.PlainDate,
    serialize: (v) => v.toJSON(),
    deserialize: (v) => Temporal.PlainDate.from(v),
  },
  "Temporal.PlainDate"
)

where is attempt attempt(() => ) coming from?