found a neat use for 's new opaque type aliases: type safe stringified values. errors if an unknown/arbitrary string is passed
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Was wanting this recently for tagging various IDs. Would really reduce the chance of mixing them up and allow for type-driven refactors.
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Isn't it still safer / easier to enumerate possible values in `type S = 'someid' | 'otherid'`? Works even in the same file.
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if it's practical to enumerate all valid ids, sure, but if eg. valid ids = string of any number in a large range then it's not practical
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Ah yeah, agree, TS and Flow always felt a bit limited in that regard (I'd love to be able to specify regexp as a type).
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Opaque types plus a fallible constructor function could help with that! Check the regex in the function :)
Nah, I don't want it to be a runtime check, exactly the opposite. E.g. to strengthen defs of parseInt and similar funcs.
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