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

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>, }