What is the arktype 2 syntax for inferring classes with a private constructor?

In Arktype 1.x I was writing:

import { type, Infer } from 'arktype';

const document = type({
    "ttl?": ["instanceof", TimeStub] as Infer<TimeStub>,
})

import { type, Infer } from 'arktype';

const document = type({
    "ttl?": ["instanceof", TimeStub] as Infer<TimeStub>,
})

But the Infer import is not more available in arktype 2, so I'm wondering how to achieve it now? Maybe the answer could be also added to the docs 🙂 https://arktype.io/docs/objects#instanceof

5 Replies

MichaOP•3w ago

Seems I'm getting a bit closer:

const document = type({
  "ttl?": type.instanceOf(TimeStub) as type.infer<TimeStub>,
});

const document = type({
  "ttl?": type.instanceOf(TimeStub) as type.infer<TimeStub>,
});

But this throws a conversion error:

Conversion of type 'Type<TimeStub, {}>' to type '{ isoString: never; toDate: {}; toString: {}; }' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
  Type 'Type<TimeStub, {}>' is missing the following properties from type '{ isoString: never; toDate: {}; toString: {}; }': isoString, toDatets(2352)

Conversion of type 'Type<TimeStub, {}>' to type '{ isoString: never; toDate: {}; toString: {}; }' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
  Type 'Type<TimeStub, {}>' is missing the following properties from type '{ isoString: never; toDate: {}; toString: {}; }': isoString, toDatets(2352)

If I cast it to unknown

export const document_update = type({
  "ttl?": type.instanceOf(TimeStub) as unknown as type.infer<TimeStub>,
});

export const document_update = type({
  "ttl?": type.instanceOf(TimeStub) as unknown as type.infer<TimeStub>,
});

then I get again back to the initial error:

Argument of type 'typeof TimeStub' is not assignable to parameter of type 'Constructor<TimeStub>'.
  Cannot assign a 'private' constructor type to a 'public' constructor type.ts(2345)

Argument of type 'typeof TimeStub' is not assignable to parameter of type 'Constructor<TimeStub>'.
  Cannot assign a 'private' constructor type to a 'public' constructor type.ts(2345)

ssalbdivad•3w ago

https://arktype.io/docs/expressions#cast

MichaOP•3w ago

Like this?

export const document_update = type({
  "ttl?": TimeStub as type.cast<TimeStub>,
});

export const document_update = type({
  "ttl?": TimeStub as type.cast<TimeStub>,
});

ssalbdivad•3w ago

That would work

MichaOP•3w ago

Awesome - you're a live saver! ❤️

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What is the arktype 2 syntax for inferring classes with a private constructor?

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