An attachment to comment on https://www.pragmaticobjects.com/chapters/001_checked_exceptions.html

ErrorHandling.java

// Java(?) way
interface Fraction<E extends Exception> {
    int numerator() throws E;
    int denominator() throws E;
}
class FracStatic implements Fraction<RuntimeException> // don't force catching
class FracSum<E1, E2> implements Fraction<EitherException<E1, E2>> // impossible due to type erasure


// Kotlin, Scala, Rust way
interface Fraction<E> {
    Either<E, Integer> numerator();
    Either<E, Integer> denominator();
}
class FracStatic implements Fraction<Nothing> // return type `Either<Nothing, Integer>` means that error could not happen
class FracSum<E1, E2> implements Fraction<Either<E1, E2>> { // can fail in any of two ways
    // this is ugly but possible!
}