[swift-evolution] specialize a generic type in a method

[Charlie Monroe]

Something like this should work:

protocol P1 {
	associatedtype T
	func foo(t: T)
	func bar<U where U == T, U: Equatable>(t: U)
}


> On Jun 20, 2016, at 8:07 PM, Vladimir.S <svabox at gmail.com> wrote:
> 
> Thank you for reply. Yes, seems this could be solved by extension. No other solutions?
> 
> But how should I be if I need such a protocol?
> 
> protocol P1 {
>    associatedtype T
>    func foo(t: T)
>    func bar(t: T) // where T:Equatable  ??
> }
> 
> I.e. I need to specify T & Equatable for bar in requirements
> 
> On 20.06.2016 20:03, Charlie Monroe wrote:
>> This is IMHO better solved via an extension - it even makes more sense to put together methods whose use is limited only to certain generics constraint:
>> 
>> extension Foo where I: Equatable {
>> 
>> 	func bar(i: I) {
>> 		///
>> 	}
>> 
>> }
>> 
>> 
>>> On Jun 20, 2016, at 6:57 PM, Vladimir.S via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> Should we be able to specialize a generic type in a method, if that generic type declared in type's definition like here? :
>>> 
>>> struct Foo<I> {
>>>   func bar(i: I) where I: Equatable { } // should this work?
>>> }
>>> 
>>> As I understand, for concrete instance of foo: Foo<X>, if X is not Equatable, then compiler should prevent us from calling foo.bar(x)
>>> 
>>> Or, probably, the better way to express this could be :
>>> 
>>>   func bar(i: I & Equatable) { }
>>> or
>>>   func bar(i: Any<I, Equatable>) { }
>>> 
>>> Can't check if it possible now because my compiler crashes because of 'where I:Equatable' text (submitted to bugs.swift.org)
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>> 
>>