<E>(left: E): Result<never, E>Creates a Result holding a Failure value.
When to use
Use to represent a failed Result with a typed failure value.
Details
- The success type
Adefaults tonever
Example (Creating a failure)
import { Result } from "effect"
const result = Result.fail("Something went wrong")
console.log(Result.isFailure(result))
// Output: trueSource effect/Result.ts:3141 lines
export const const fail: <E>(
left: E
) => Result<never, E>
Creates a Result holding a Failure value.
When to use
Use to represent a failed Result with a typed failure value.
Details
- The success type
A defaults to never
Example (Creating a failure)
import { Result } from "effect"
const result = Result.fail("Something went wrong")
console.log(Result.isFailure(result))
// Output: true
fail: <function (type parameter) E in <E>(left: E): Result<never, E>E>(left: Eleft: function (type parameter) E in <E>(left: E): Result<never, E>E) => type Result<A, E = never> = Success<A, E> | Failure<A, E>A value that is either Success<A, E> or Failure<A, E>.
When to use
Use when both success and failure should remain available as data and
Option would lose failure information.
Details
- Use
succeed
/
fail
to construct
- Use
match
to fold both branches
- Use
isSuccess
/
isFailure
to narrow the type
E defaults to never, so Result<number> means a result that cannot fail.
Example (Creating and matching a Result)
import { Result } from "effect"
const success = Result.succeed(42)
const failure = Result.fail("something went wrong")
const message = Result.match(success, {
onSuccess: (value) => `Success: ${value}`,
onFailure: (error) => `Error: ${error}`
})
console.log(message)
// Output: "Success: 42"
Namespace containing type-level utilities for extracting the inner types
of a Result.
Example (Extracting inner types)
import type { Result } from "effect"
type R = Result.Result<number, string>
// number
type A = Result.Result.Success<R>
// string
type E = Result.Result.Failure<R>
Result<never, function (type parameter) E in <E>(left: E): Result<never, E>E> = import resultresult.const fail: <E>(
failure: E
) => Result.Result<never, E>
Referenced by 32 symbols
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