Tuple transformation: tuple type lost after mapping

[devjourney5]

Following transformation on tuple loses tuple information:

function pack(args: [...any[]]) {
  return args.map(a => String(a))
}
var tuple: [number, number] = [5, 5]
var packed = pack(tuple) // string[]

Expected behavior:
packed is of type [string, string]

Actual behavior:
packed is of type string[]

How can preserve tuple length and element types after transforming it via function, assuming I dont know length of tuple at design time?

[mattmccutchen]

Currently you can't. See #25947 for the suggestion and a current workaround.

[typescript-bot]

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