isUnexpected not working if one model is a subset of another model

[MaryGao]

See pr https://github.com/Azure/autorest.typescript/pull/2501/files
Generated code: https://github.com/kazrael2119/autorest.typescript/blob/deviceregistry-modular/packages/typespec-test/test/DeviceRegistry.Management/generated/typespec-ts/src/rest/isUnexpected.ts#L82

In following OperationStatusGetDefaultResponse is a subset of OperationStatusGet200Response so the helper fail to type narrowing.

export function isUnexpected(
  response: OperationStatusGet200Response | OperationStatusGetDefaultResponse,
): response is OperationStatusGetDefaultResponse;

Finally causing the modular code failed to compile.

[qiaozha]

need further discussion on the typespec best practice.

[MaryGao]

The definition is designed in v3 common models https://github.com/Azure/azure-rest-api-specs/blob/main/specification/deviceregistry/resource-manager/Microsoft.DeviceRegistry/preview/2023-11-01-preview/deviceregistry.json#L192-L204.