```fun a() : Either<DomainError, Int> = either { val a = getById(1).bind() if (a.isPub...

# arrow

[S.]

fun a() : Either<DomainError, Int> = either {
    val a = getById(1).bind()
    if (a.isPublic) return@either DomainError().left()
    a.id
}

Why does return@either Error.left() affect the Either.Right here? I'm getting
Type mismatch. Required: Int Found: Either<DomainError, Nothing . DomainError().left().bind() would comply with the signature but warns that ``Returning type parameter has been inferred to Nothing implicitly` . What is the proper way to return early with a Either.Left in such a case?

[streetsofboston]

I think calling "if (a.isPublic) shift(DomainError())" may work, or "if (a.isPublic) DomainError().left().bind()"

[streetsofboston]

In the ”either" lambda you must return a value of the Right's type (Int). To cause this "either {...}" to return an Either.Left type (DomainError) you need to shortcut the lambda by binding to an Either.Left, or by shifting to an error (I'm a bit rusty on the shifting and such 😁, but I think explained the gist of it)

[S.]

yeah thanks. Though I'm not sure which type B is supposed to be. fun <B> shift(r: R): B because it cannot be inferred. In Effect it states that both, A and R are mapped to B. DomainError().left().bind() infers Nothing but with a warning that it could produce runtime exceptions.

[julian]

It looks like B is Int, in your case.

[S.]

Okay, thanks for the clarification

[okarm]

Relevant: The return type of shift was changed to `Nothing`: https://github.com/arrow-kt/arrow/issues/2810

Arguably that should always have been the case - execution does not continue after shift. It's akin to other Nothing producers such as return or throw.