Discriminated unions with common field but different constraints

interface BaseEntity {
    id: number;
    name: string;
    someField: string | null; // By default, someField can be null
}

interface EntityA extends BaseEntity  {
    type: "typeA";
    someField: string;  // someField cannot be null for typeA
}

interface EntityB extends BaseEntity  {
    type: "typeB";
}


type MyEntity = EntityA | EntityB;

export default MyEntity;

import { type } from "arktype"

const BaseSchema = type({
  name: "string",
  someField: "string | null",
});

const ASchema = BaseSchema.and({
  type: "'typeA'",
  someField: "string",
});

const BSchema = BaseSchema.and({
  type: "'typeB'",
});


export const MySchema = ASchema.or(BSchema);
export type MySchemaType = typeof MySchema.infer;