Better support for Enums in Collection methods

[ProgrammerZ]

It would greatly improve if we had better support for Enums in collection methods, so we don't have to do something like this when working with collection of Enums.

$col_1 = collect([Enum::CaseOne, Enum::CaseTwo]);
$col_2 = collect([Enum::CaseOne]);

$col_1->diffUsing($col_2, function ($a, $b) {
    return $a->value <=> $b->value;
});

[shaedrich]

It would be nice to have something like this:

interface Diffable
{
    public function diff(self $a, self $b): bool;
}

or

interface Diffable
{
    /**
     * Diffs `$this` with `$other`
     */
    public function diff(self $other): bool;
}

or

interface Diffable
{
    /**
     * Diff will be called on the result of
     * $this->toDiffable()` instead of `$this`
     */
    public function toDiffable();
}