    "Given two [[Comparable]] values, return largest of the two.

     If exactly one of the given values violates the reflexivity
     requirement of [[Object.equals]] such that `x!=x`, then the
     other value is returned. In particular, if exactly one is
     an [[undefined `Float`|Float.undefined]], it is not
     returned.

     _On the JVM platform, for arguments of type `Integer` or
     `Float`, prefer [[Integer.largest]] or [[Float.largest]]
     in performance-sensitive code._"
    see (`interface Comparable`,
         `function smallest`,
         `function max`,
         `function Integer.largest`,
         `function Float.largest`)
    tagged("Comparisons")
    shared Element largest<Element>(Element x, Element y)
            given Element satisfies Comparable<Element>
            => if (x!=x || y>x) then y else x;