Feature Request: Support of discriminated Union Types

[paulwer]

When using discriminated unions by a class-validator (at)Type() function the infer fails, because it will not pass a valid variable to the type function.

class StringType {
  @IsIn(['stringType'])
  type!: 'stringType';

  @IsString()
  stringVal!: string;
}

class NumberType {
  @IsIn(['numberType'])
  type!: 'numberType';

  @IsNumber()
  numVal!: number;
}

class BooleanType {
  @IsIn(['booleanType'])
  type!: 'booleanType';

  @IsBoolean()
  boolVal!: boolean;
}

class DiscriminatedUnionType {
  @IsIn(['stringType', 'numberType', 'booleanType'])
  type!: 'stringType' | 'numberType' | 'booleanType';

  @ValidateNested()
  @Type((obj) => {
    switch (obj?.object.type) {
      case 'stringType':
        return StringType;
      case 'numberType':
        return NumberType;
      case 'booleanType':
        return BooleanType;
      default:
        throw new Error(`Invalid type: ${obj?.object.type}`);
    }
  })
  element!: StringType | NumberType | BooleanType;
}

export class NestedUnionSchema {
  @ArrayNotEmpty()
  @ValidateNested({ each: true })
  @Type(() => DiscriminatedUnionType)
  elements!: DiscriminatedUnionType[];
}

Any suggestions how to change the classes or could this be a supported feature in the future?