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This can be done using [conditional types](https://www.typescriptlang.org/docs/handbook/2/conditional-types.html).

I defined these helper types:
```typescript
enum Role { server, client };
type PossiblyHiddenFromClients<R extends Role, T> =
  T | (R extends Role.client ? undefined : never);
```

When R is `server`, this type reduces to `T` (via `T | never`); when R is `client`, it is `T | undefined`.

`User` can then be defined as:
```typescript
type User<R extends Role> = {
  name: string;
  superSecretGovernmentIdNumber: PossiblyHiddenFromClients<R, string>;
};
```

There are now two types, `User<Role.server>` representing a full unredacted user, and `User<Role.client>` representing one that may or may not have information missing. The client should always use the latter; the server uses the former internally and converts to the latter (redacting as required) when returning data to the client.