Define a UoM which can only be created from a "constructor"

PrivateUoM.fsx

module Units =

    [<Measure>] type private Chicken

    module Chicken =

        let create x =
            if x < 0 then
                invalidArg (nameof x) "Cannot have a Chicken <0"

            LanguagePrimitives.Int32WithMeasure<Chicken> x

open Units


let myChicken = Chicken.create 1

// The "normal" way to add UoM annotation to a primitive
let failChicken = LanguagePrimitives.Int32WithMeasure<Chicken> 1
let otherFailChicken = 1 * 1<Chicken>