> On Jul 9, 2017, at 10:06, David Baraff via swift-users
> <swift-users@swift.org> wrote:
>
>
>> On Jul 9, 2017, at 8:27 AM, Jens Persson <j...@bitcycle.com> wrote:
>>
>> (Also, note that your implementation of == uses lhs === rhs thus will only
>> return true when lhs and rhs are the same instance of SomeClass.)
> Of course — i threw that in just to make a simple example.
>
> Followup question: what I really wanted to write was an == operator for a
> tree:
>
> // silly tree, useful for nothing
> class Tree : Equatable {
> let rootData:Int
> let children:[(String, Tree)]
>
> static public func ==(_ lhs:Tree, _ rhs:Tree) {
> return lhs.rootData == rhs.rootData &&
> lhs.children == rhs.children // sadly, this doesn’t
> compile
> }
> }
Right, the `==` func is *defined* for 2-element tuples where both elements
conform to `Equatable`, but that tuple type doesn't itself *conform* to
`Equatable`. So the`==` func that's defined on "Array where Element: Equatable"
can't see it.
We'd need both "conditional conformance" and "tuple conformance" in order for
that to Just Work.
- Dave Sweeris
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