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Comment by klodolph | Hacker News Reader

It’s not just syntax, there are semantic problems.

Like, function 1 fails for reason A or B. Function 2 fails for A or C. You call both functions. How do you pattern match on reason A, in the result of your function?

In Go, there’s a somewhat simple pattern for this, which is errors.Is().

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It's a tradeoff. When you have a "flat" union like `A | B | C` that makes it easy to pattern-match "leaf" errors, you give up the ability to add any additional context in function1 and function2. Although, there are workarounds like

    struct Error {
        leaf_error: A | B | C,
        context: Vec<String>,
    }

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