Class Err<E>

constructor

• new Err<E>(error: E): Err<E>

  Type Parameters

  • E

  Parameters

  • error: E

  Returns Err<E>

Readonlyerror

[iterator]

• "[iterator]"(): Generator<Err<E>, never>

  Enables yield* res inside a result.gen body — the equivalent of Rust's ? operator.

  On Ok, yield* produces no yields and evaluates to the contained value. On Err, it yields the Err itself, which the surrounding result.gen / genSync / genAsync driver returns by reference (short-circuiting the rest of the body). Not meant to be iterated by anything other than those drivers.

  Returns Generator<Err<E>, never>

and

• and(_res: unknown): this

  Returns res if this result is Ok, otherwise returns this Err.

  res is evaluated eagerly; prefer andThen when it comes from a function call that should run only after Ok.

  Parameters

  • _res: unknown

  Returns this

  res on Ok, or this on Err.

  See

  Result::and

andThen

• andThen(_fn: unknown): this

  Calls fn if this result is Ok, otherwise returns this Err.

  Use to chain fallible steps that return another Result.

  Parameters

  • _fn: unknown

  Returns this

  The Result from fn, or this on Err.

  See

  Result::and_then

expect

• expect(message: string): never

  Returns the contained Ok value.

  Prefer narrowing (isOk / isErr) or non-throwing helpers (unwrapOr, unwrapOrElse) when the Err case is expected.

  Parameters

  • message: string

    Included in the thrown Error when this result is Err (describe why you expected Ok, as in Rust's expect docs).

  Returns never

  The success value.

  Throws

  When the result is Err.

  See

  Result::expect

inspect

• inspect(_fn: unknown): this

  Calls fn with the contained Ok value, then returns this unchanged.

  Callbacks receive DeepReadonly views (compile-time only; no runtime freeze).

  Parameters

  • _fn: unknown

  Returns this

  this (for chaining).

  See

  Result::inspect

inspectErr

• inspectErr(fn: (error: DeepReadonly<E>) => void): this

  Calls fn with the contained Err value, then returns this unchanged.

  Parameters

  • fn: (error: DeepReadonly<E>) => void

    Side effect for the error value; not called on Ok.

  Returns this

  this (for chaining).

  See

  Result::inspect_err

isErr

• isErr(): this is Err<E>

  Returns true if the result is Err.

  Returns this is Err<E>

  See

  Result::is_err

isOk

• isOk(): this is never

  Returns true if the result is Ok.

  Returns this is never

  See

  Result::is_ok

map

• map<_>(_fn: unknown): this

  Maps Result<T, E> to Result<U, E> by applying fn to the contained Ok value, leaving an Err untouched.

  Type Parameters

  • _

  Parameters

  • _fn: unknown

  Returns this

  A new Result with the mapped Ok value, or the original Err.

  See

  Result::map

mapErr

• mapErr<E2>(fn: (error: E) => E2): Err<E2>

  Maps Result<T, E> to Result<T, F> by applying fn to the contained Err value, leaving an Ok untouched.

  Type Parameters

  • E2

  Parameters

  • fn: (error: E) => E2

    Transforms the error value.

  Returns Err<E2>

  A new Result with the mapped Err value, or the original Ok.

  See

  Result::map_err

mapOr

• mapOr<U1, _>(defaultValue: U1, _fn: unknown): U1

  Returns defaultValue if Err, or applies fn to the contained Ok value.

  Both arguments are evaluated eagerly; prefer mapOrElse when the fallback should run only on Err.

  Type Parameters

  • U1
  • _

  Parameters

  • defaultValue: U1

    Value returned when this result is Err.

  • _fn: unknown

  Returns U1

  See

  Result::map_or

mapOrElse

• mapOrElse<U1, _>(defaultValue: (error: E) => U1, _fn: unknown): U1

  Maps a Result to U by applying onErr to a contained Err value, or onOk to a contained Ok value.

  Type Parameters

  • U1
  • _

  Parameters

  • defaultValue: (error: E) => U1
  • _fn: unknown

  Returns U1

  See

  Result::map_or_else

or

• or<R extends Result<OkContent<R>, ErrContent<R>>>(res: R): R

  Returns res if this result is Err, otherwise returns this Ok.

  res is evaluated eagerly; prefer orElse for lazy fallbacks.

  Type Parameters

  • R extends Result<OkContent<R>, ErrContent<R>>

  Parameters

  • res: R

    Alternate result when this result is Err.

  Returns R

  this on Ok, or res on Err.

  See

  Result::or

orElse

• orElse<R extends Result<OkContent<R>, ErrContent<R>>>(fn: (error: E) => R): R

  Calls fn if this result is Err, otherwise returns this Ok.

  Type Parameters

  • R extends Result<OkContent<R>, ErrContent<R>>

  Parameters

  • fn: (error: E) => R

    Called with the error when this result is Err.

  Returns R

  The Result from fn, or this on Ok.

  See

  Result::or_else

unwrap

• unwrap(): never

  Returns the contained Ok value.

  Returns never

  The success value.

  Throws

  When the result is Err (message derived from the error).

  See

  Result::unwrap

unwrapErr

• unwrapErr(): E

  Returns the contained Err value.

  Returns E

  The error value.

  Throws

  When the result is Ok.

  See

  Result::unwrap_err

unwrapOr

• unwrapOr<T2>(defaultValue: T2): T2

  Returns the contained Ok value, or defaultValue if the result is Err.

  Type Parameters

  • T2

  Parameters

  • defaultValue: T2

    Value to return when this result is Err (evaluated eagerly).

  Returns T2

  T on Ok, otherwise defaultValue.

  See

  Result::unwrap_or

unwrapOrElse

• unwrapOrElse<T2>(fn: (error: E) => T2): T2

  Returns the contained Ok value, or computes it from the Err value.

  Type Parameters

  • T2

  Parameters

  • fn: (error: E) => T2

    Called with the error when this result is Err.

  Returns T2

  T on Ok, otherwise the value returned by fn.

  See

  Result::unwrap_or_else