I think I just described 20 lines of shell haha. But I think there's good value to be had here, which is the important part.
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Option has or_else which you can return another Option from, and `ok_or_else(fn)` which turns an Option<T> into a Result<T, E> in a similar way https://doc.rust-lang.org/std/option/enum.Option.html#method.ok_or_else …
Yeah, but I'm still not seeing any way where we can handle errors inside the None branch. How would the initial example be expressed with these statements? I feel like I'm missing something obvious?
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let node = self.cache.get(key) // Option<K> .ok_or_else(|| self.db.get(key))?; // Result<K, E> can be ?-ed // node is now a K
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Ahhh, yeah I see where you're going. But believe there's a mistake there. The type returned by the closure will end up being: Result<Result<K, E>, E> Which is incompatible with the return type from `self.cache.get()`. So we'd still need to do `self.db.get(key).unwrap()` :(
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