/* Setup */
class SuccessResult<T> {
  success: true = true;
  constructor(public value: T) {}
  throwOnFailure(): asserts this is SuccessResult<T> {}
  isSuccess(): this is SuccessResult<T> {
    return this.success;
  }
}

class FailureResult<T, E extends Error> {
  success: false = false;
  constructor(public error: E) {}
  throwOnFailure(): asserts this is SuccessResult<T> {
    throw this.error;
  }
  isSuccess(): this is SuccessResult<T> {
    return this.success;
  }
}

type OperationResult<T = never, E extends Error = Error> =
  | SuccessResult<T>
  | FailureResult<T, E>;

function workingAssertGuard<T>(result: OperationResult<T>): asserts result is SuccessResult<T> {
  if (!result.success){
    throw result.error
  }
}
/* End Setup */



const result: OperationResult<string> = {} as OperationResult<string>

/* This is the issue */
function assertThisType(){
  result.throwOnFailure()
  // type is unchanged
  result // OperationResult<string, Error>
}
/* End of issue */


/* The rest below works as intended */
function narrowOnProperty(){
  // Working narrowing from prop
  if (result.success){
    result.value // SuccessResult<string>
  } else {
    result.error // FailureResult<string, Error>
  }

}

function assertTypeGuard(){

  // Working narrowing from Assert Type Guard Function 
  workingAssertGuard(result)
  result.value // SuccessResult<string>

}

function narrowThisTypeGuard(){
 // Working narrowing from boolean Type Guard Member Function 
    if (result.isSuccess()) {
    result.value // SuccessResult<string>
  } else {
    result.error // FailureResult<string, Error>
  }
}