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i can't imagine why you would want that. for example, why would i want something defined as an integer hold something other than an integer? this is how strongly-typed languages work.

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Scott Wlaschin's "F# For Fun and Profit" website is a great resource for strongly-typed (yes) data modeling with sum types as a fundamental tool.

https://fsharpforfunandprofit.com/series/designing-with-type...

By the third entry in the linked series, we've motivated the use of a sum type with three variants in the example domain model.

You definitely want an integer to always be an integer, but you often want to represent "A or B". E.g. user has a contact method that's a phone number or an email address. Result of validation is a validated value or a failure message.

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