kotlin-stdlib/com.javiersc.kotlin.stdlib/Either/leftOrNull

leftOrNull

Returns the unwrapped value A of Either.Left or null if it is Either.Right.

import arrow.core.Either
import io.kotest.matchers.shouldBe

fun test() {
  Either.Right(12).leftOrNull() shouldBe null
  Either.Left(12).leftOrNull() shouldBe 12
}