Working on Project Euler, I come across a lot of situations where I need to use bigint -- but would rather be able to use it seamlessly.

sqrt is implemented like this:

let inline sqrtImpl(x: ^T) : ^U =

(^T: (static member Sqrt : ^T -> ^U) (x))

when ^T : float = System.Math.Sqrt(retype x : float)

when ^T : float32 = System.Math.Sqrt(toFloat (retype x)) |> toFloat32

I tried to do something similar to make a more generic "even" function, like this:

let evenI (x:^T) : ^T =

when ^T : bigint = x % 2I = 0I

when ^T : int = x % 2 = 0

But I get this error:

Static optimization conditionals are only for use within the F# library

Is there any better way to do this so that I don't have to keep messing with changing all my int implementations of everything to bigint?