Consider adding Result.requireNonNull

I really like this library! I just found myself wanting a function that takes a nullable value and makes sure that it is not null by turning it into an Error value if it is null (useful for the many dotnet function that might return null). Would you consider a PR that adds something like the code below?

let requireNotNull (errorValue : 'error) (value : 'a when 'a : null ) =
    match value with
    | null -> Error errorValue
    | nonnull -> Ok nonnull

[cmeeren]

The helper function makes sense to me. 🙂

I’d call it requireNotNull (as OP suggested) instead of requireNonNull though, to fit with other functions (e.g. notEqualTo) (and in my mind it sounds better), but I certainly don’t want to create a fuss over the difference.

[danyx23]

Looks good. I have some strange issue with the update of the nuget file in the project that I am using this but the assembly has the new code and everything should work so I’m closing the issue.