Hi Rudolf,
What you are describing is not possible right now. The protocol PointType
cannot be used as a type at all, because it has an associated type requirement.
Also it is not clear what a ‘where’ clause attached to a type alias would mean.
There has been some discussion of ‘generalized existentials’ on the evolution
list. So eventually, you might be able to say something like this:
typealias Point = Any<Point : PointType where Point.Float == Float>
Slava
> On Sep 4, 2017, at 6:12 PM, Rudolf Adamkovič via swift-users
> <swift-users@swift.org> wrote:
>
> I have the following ProceduralDrawing type:
>
> public struct ProceduralDrawing<Float, Point: PointType> where Point.Float ==
> Float {
> // ... code that used Float and Point ...
> }
>
> public protocol PointType {
> associatedtype Float: FloatingPoint
> var x: Float { get }
> var y: Float { get }
> }
>
> I would like to avoid adding Point as a generic parameter but the following
> doesn’t work:
>
> public struct ProceduralDrawing<Float: FloatingPoint> {
> // ERROR: 'where' clause cannot be attached to a non-generic declaration
> typealias Point = PointType where Point.Float == Float
> // ... code that uses Float and Point ...
> }
>
> Is there a way to do this? If not, why?
>
> Thanks!
>
> R+
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