[remexre]

I think it's fair to say that having some sort of syntactically lightweight sum or union type facility makes this way nicer than anything Java ever had -- subclassing isn't really a solution, because you often want something like:

    type FooError = YoureHoldingItWrong | FileError
    type BarError = YoureHoldingItWrong | NetworkError
    fn foo() -> Result<int, FooError> { ... }
    fn bar() -> Result<int, BarError> { ... }
    fn baz() -> Result<String, BarError> { ... }

TypeScript's type system would hypothetically make this pretty nice if there were a common Result type with compiler support.

Rust needs a bit more boilerplate to declare FooError, but the ? syntax automatically calling into(), and into() being free to rearrange errors it bubbles up really help a lot too.

The big problem with Java's checked exceptions was that you need to list all the exceptions on every function, every time.

[esafak]

Java's sealed interfaces enable typing errors.

https://blogs.oracle.com/javamagazine/post/java-sealed-class...

[keybored]

Although syntactically lightweight it is the opposite of.

[esafak]

I agree; Java is constitutionally incapable of being lightweight. I much prefer Typescript's union syntax. I'm glad Python copied it.

[peterashford]

records are lightweight