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eliminating wildcard match on enum
f#

Is there a way to get rid of the wildcard case when matching on a C# enum?

I get the following error when matching without the wildcard case:

Incomplete pattern matches on this expression. For example, the value '0' may indicate a case not covered by the pattern(s).

.

No. (The same problem exists in C#, various static-analysis tools will force/encourage you to write a "default" clause in your 'switch'.) This is just a consequence of .Net enums being represented by an underlying integer type that contains more possible values than there are in an enumeration.

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type MyEnum =
    | One = 1
    | Two = 2

let f x =
    match x with
    | MyEnum.One -> "one"
    | MyEnum.Two -> "two"
    | _ -> failwith "some other bad value"


let s = f (enum 0)
By on 1/13/2010 8:35 AM ()

You can disable the warning, but in that case you'll probably miss it in many other places where it would be useful (so it is probably not a good idea to do this). Anyway:

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#nowarn "25"
let f x =
    match x with
    | MyEnum.One -> "one"
    | MyEnum.Two -> "two"

As far as I know, this can be done only in a per-file scope, so it's not as useful.

By on 1/13/2010 9:30 AM ()

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