ad133 on That Shouldn't Happen – UnreachableException in .NET 7

Comment on That Shouldn't Happen – UnreachableException in .NET 7 parent

This was my initial thought as well, but from the text I gather there is a flow like this:

[Input Data, maybe null] -> Validate field is not null -> Call this method with the assertion.

This is a small bug-bear for me with nullable types and I wish there was a better way to do it, but many languages allow you to smart-cast away nulls, but only within the local scope. If you want to pass a struct-type around which has nullable fields, but you have already checked for non-null (like this one) you need to convert to a different struct-type, which doesn't have the nullability on its fields. I can't think of a good way round this - as you say with the unit test remark, there is nothing to stop another piece of code calling this method with nulls.

piaste 3y

If you want to pass a struct-type around which has nullable fields, but you have already checked for non-null (like this one) you need to convert to a different struct-type, which doesn't have the nullability on its fields.

Which is exactly what IMO the author should have done. It's actually a reasonable use-case for inheritance:

    #nullable enable

    record SlackEvent
        ( int EventId
        , string Content
        , string? TeamId
        );

    record TeamSlackEvent
        ( int EventId
        , string Content
        , string TeamId
        ) 
        : SlackEvent
            ( EventId : EventId
            , Content : Content
            , TeamId : TeamId
            );

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