Branded types

Feature request: branded types This issue can be the primary discussion ground for implemented branded types.

Option 1: Replicating io-ts’s symbol trickery to create types like NonZeroNumber or Email (it might be difficult to do that one while remaining ergonomic)

I don’t love all the boilerplate associated with io-ts branded types (i.e. interface PositiveBrand { readonly Positive: unique symbol }).

Option 2

It may be able to include string/number validators as a literal generic argument of the ZodString/ZodNumber classes, like so:

const num: z.number({ max: 5 }) // => z.ZodString
const max5: z.number({ max: 5 }) // => z.ZodString<{ max: 5 }>

That way the validations being enforced are easy to see with a glance at the type definition. This would only work for built-in validators I believe (?). This is also different, in that validations are registered at the instance level instead of the class level.

[colinhacks]

This is the recommended way to do tagged/branded types in TypeScript/Zod:

type Tagged<T, Tag> = T & { __tag: Tag };
type UUID = Tagged<string, 'UUID'>;

const uuid: z.Schema<UUID> = z.string().uuid() as any;
uuid.safeParse('ae6cd9c2-f2e0-43c5-919c-0640b719aacf'); // Success, data has type UUID
uuid.safeParse(5); // Fail
uuid.safeParse('foo'); // Fail

[danielo515]

This is the recommended way to do tagged/branded types in TypeScript/Zod:

type Tagged<T, Tag> = T & { __tag: Tag };
type UUID = Tagged<string, 'UUID'>;

const uuid: z.Schema<UUID> = z.string().uuid() as any;
uuid.safeParse('ae6cd9c2-f2e0-43c5-919c-0640b719aacf'); // Success, data has type UUID
uuid.safeParse(5); // Fail
uuid.safeParse('foo'); // Fail

Is there any way without using any?