[swift-users] Type "T?" does not conform to protocol 'Equatable'

[Keith Duvall]

Don’t mark it as optional in the generic definition. Mark it as optional in your implementation.

class C<T: Equatable> {
	let t: T?
	init(t: T?) {
		self.t = t
	}
}

let a = C<Int>(t: nil)

print(a.t) // nil

let b = C<Int>(t: 5)

print(b.t) // Optional(5)

Keith


> On Feb 29, 2016, at 9:24 AM, Rudolf Adamkovič via swift-users <swift-users at swift.org> wrote:
> 
> Hi everyone!
> 
> I have a generic class similar to this one:
> 
> class C<T: Equatable> {
>     let t: T
>     init(t: T) { self.t = t }
> }
> 
> When try to wrap ‘Int?' inside, I get the following error:
> 
> let a = C<Int?>(t: nil) // ERROR: Type "Int?" does not conform to protocol 'Equatable'
> 
> Yet when I try to compare two ‘Int?’ values, everything works:
> 
> let a: Int? = 5
> let b: Int? = 6
> 
> let c = a == b // NO ERROR
> 
> So, is ‘Int?' equatable or not?
> 
> Thanks!
> 
> R+
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