> On May 15, 2016, at 11:55 AM, Neil Faiman via swift-users
> <swift-users@swift.org> wrote:
>
> Is this a relatively new language change? When I try it with the version of
> Swift that comes with Xcode 7.3.1, I get
>
> error: same-type requirement makes generic parameters 'T1' and 'T2'
> equivalent
> extension Foo where T1 == T2 {
> ^
Unfortunately, it's a limitation of our type system today that
class/struct/enum extensions can't use '==' constraints. It can often be worked
around by making a protocol instead.
-Joe
>
>> On May 15, 2016, at 1:33 PM, Karl <razie...@gmail.com> wrote:
>>
>> Yes. You need to put it in an extension.
>>
>> extension Foo where T1 == T2 {
>> convenience init(values: [T1]){
>> ….
>> }
>> }
>>
>>> On 15 May 2016, at 14:45, Neil Faiman via swift-users
>>> <swift-users@swift.org> wrote:
>>>
>>> Is it possible for a generic class to have methods (specifically,
>>> initializers) which are only defined if the generic parameters meet certain
>>> constratins?
>>>
>>> Here’s a concrete example:
>>>
>>> class Foo <T1, T2> {
>>> init(pairs: [(T1, T2)]) {}
>>> // What I’d like to be able to doL
>>> convenience init "where T1 == T2" (values: [T1]) { self.init(pairs:
>>> values.map{ ($0, $0) }) }
>>> }
>>>
>>> That is, I’d like to provide a convenience initializer that takes an array
>>> of values instead of pairs, and turns the values into pairs, IF THE TWO
>>> GENERIC TYPE PARAMETERS ARE THE SAME.
>>>
>>> I can’t find a way to accomplish this. Is there one?
>
>
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