Sorry about the typo (filenames for the code were mentioned wrong).
The corrected filenames are as follows (problem still occurs):
Question:
- Why does the error occur when extension CarID : P2 {} is defined in
CarID.swift ?
CreateCars.swift:
import Foundation
protocol P1 {
associatedtype ItemID
}
class Car : P1 {
typealias ItemID = CarID
}
//extension CarID : P2 {} //Error wouldn't occur if this line is uncommented
and the line in CarID.swift is commented out
protocol P2 {}
class CreateItems<Something : P1>
where Something.ItemID : P2 {}
class CreateCars : CreateItems<Car> {} //Error: Type 'Car.ItemID' (aka 'CarID')
does not conform to protocol 'P2'
extension CreateCars {}
CarID.swift:
import Foundation
class CarID {}
extension CarID : P2 {} //If this line is moved to CreateCars.swift the error
vanishes away
Thanks and regards,
Muthu
> On 17 Sep 2017, at 10:55 AM, somu subscribe via swift-users
> <swift-users@swift.org> wrote:
>
> Hi,
>
> When using Generics with Protocols I get a compilation error depending on
> whether or not conformance to a protocol is defined in the same file or not.
>
> Error:
> Type 'Car.ItemID' (aka 'CarID') does not conform to protocol 'P2'
>
> I have 2 swift files:
> - CarID.swift
> - CreateCars.swift
>
> Observations:
> - I get the error when extension CarID : P2 {} is defined in CarID.swift
> - I don’t get the error when extension CarID : P2 {} is defined in
> CreateCars.swift as shown in the comments below.
>
> Tested On:
> - Xcode 9.0 (9A235) - GM
> - Command Line project / iOS project
>
>
> CarID.swift:
>
> import Foundation
>
> protocol P1 {
> associatedtype ItemID
> }
>
> class Car : P1 {
> typealias ItemID = CarID
> }
>
> //extension CarID : P2 {} //Error wouldn't occur if this line is uncommented
> and the line in CarID.swift is commented out
>
> protocol P2 {}
>
> class CreateItems<Something : P1>
> where Something.ItemID : P2 {}
>
> class CreateCars : CreateItems<Car> {} //Error: Type 'Car.ItemID' (aka
> 'CarID') does not conform to protocol 'P2'
>
> extension CreateCars {}
>
>
>
> CreateCars.swift:
>
> import Foundation
>
> class CarID {}
>
> extension CarID : P2 {} //If this line is moved to CreateCars.swift the error
> vanishes away
>
>
> Thanks and regards,
> Muthu
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