"Determine if the arguments are [[identical]]. Equivalent to
 `x===y`. Only instances of [[Identifiable]] have 
 well-defined identity."​
​see (`function identityHash`)
​tagged("Comparisons")
​shared Boolean identical(
        "An object with well-defined identity."​
        Identifiable x, 
        "A second object with well-defined identity."​
        Identifiable y) 
                => x===y;
​