byethrow
Guide
API Reference
Guide
API Reference

Function: assertFailure()

Asserts that a Result or ResultAsync is a Failure and returns it. If the result is a Success, throws an error.

Type Param

The type of the error value.

Param

The Result or ResultAsync to assert as a Failure.

Throws

If the result is a Success.

Examples

import { Result } from '@praha/byethrow';

const result: Result.Result<number, string> = Result.fail('error');
const failure = Result.assertFailure(result);
// failure: { type: 'Failure', error: 'error' }
import { Result } from '@praha/byethrow';

const result: Result.Result<number, string> = Result.succeed(42);
Result.assertFailure(result); // throws Error
import { Result } from '@praha/byethrow';

const result: Result.Result<number, string> = getResult();
const value = Result.pipe(
  result,
  Result.andThen(() => Result.fail('die')),
  Result.assertFailure,
  Result.unwrapError(), // Safe unwrap after assertion
);

See

unwrapError - Use with assertFailure to safely unwrap error values.

Call Signature

assertFailure<R>(result): Promise<Failure<InferFailure<R>>>

Defined in: functions/assert-failure.ts:53

Type Parameters

R

R extends ResultAsync<never, any>

Parameters

result

R

Returns

Promise<Failure<InferFailure<R>>>

Call Signature

assertFailure<R>(result): Failure<InferFailure<R>>

Defined in: functions/assert-failure.ts:54

Type Parameters

R

R extends Result<never, any>

Parameters

result

R

Returns

Failure<InferFailure<R>>