experimental conditional conformances flag

mwhiteside.dev · December 6, 2017, 3:31am

Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing the new '-enable-experimental-conditional-conformances' flag to Xcode? It works when I run swift from the command line, with the Dec. 5th snapshot toolchain, but not Xcode. I have tried whats in the screenshot below as well as adding -Xfrontend, but I’m still getting the usual ‘extension of protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

Jens · December 6, 2017, 6:48am

It works for me with Xcode 9.1 and 9.2 using latest dev snapshot (from
2017-11-28 and 2017-12-03), I
added -enable-experimental-conditional-conformances in Other Swift Flags as
you show in the screenshot.
/Jens

···

On Wed, Dec 6, 2017 at 4:32 AM, Matt Whiteside via swift-users < swift-users@swift.org> wrote:

Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing
the new '-enable-experimental-conditional-conformances' flag to Xcode?
It works when I run swift from the command line, with the Dec. 5th snapshot
toolchain, but not Xcode. I have tried whats in the screenshot below as
well as adding -Xfrontend, but I’m still getting the usual ‘extension of
protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

AlexSedykh · December 6, 2017, 6:46am

Please explain, what is conditional conformances with another words?

···

Среда, 6 декабря 2017, 6:32 +03:00 от Matt Whiteside via swift-users <swift-users@swift.org>:

Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing the new '-enable-experimental-conditional-conformances' flag to Xcode? It works when I run swift from the command line, with the Dec. 5th snapshot toolchain, but not Xcode. I have tried whats in the screenshot below as well as adding -Xfrontend, but I’m still getting the usual ‘extension of protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

--

mwhiteside.dev · December 6, 2017, 7:52am

Here’s an explanation:

github.com

apple/swift-evolution/blob/main/proposals/0143-conditional-conformances.md

# Conditional conformances

* Proposal: [SE-0143](0143-conditional-conformances.md)
* Author: [Doug Gregor](https://github.com/DougGregor)
* Review Manager: [Joe Groff](https://github.com/jckarter)
* Status: **Implemented (Swift 4.2)**
* Decision Notes: [Review extended](https://forums.swift.org/t/review-se-0143-conditional-conformances/4130/10), [Rationale](https://forums.swift.org/t/accepted-se-0143-conditional-conformances/4537)
* Previous Revision: [1](https://github.com/apple/swift-evolution/blob/91725ee83fa34c81942a634dcdfa9d2441fbd853/proposals/0143-conditional-conformances.md)

## Introduction

Conditional conformances express the notion that a generic type will
conform to a particular protocol only when its type arguments meet
certain requirements. For example, the `Array` collection can
implement the `Equatable` protocol only when its elements are
themselves `Equatable`, which can be expressed via the following
conditional conformance on `Equatable`:

```swift
extension Array: Equatable where Element: Equatable {

This file has been truncated. show original

Matt

···

On Dec 5, 2017, at 22:46, Седых Александр <se-a@mail.ru> wrote:

Please explain, what is conditional conformances with another words?

Среда, 6 декабря 2017, 6:32 +03:00 от Matt Whiteside via swift-users <swift-users@swift.org>:

Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing the new '-enable-experimental-conditional-conformances' flag to Xcode? It works when I run swift from the command line, with the Dec. 5th snapshot toolchain, but not Xcode. I have tried whats in the screenshot below as well as adding -Xfrontend, but I’m still getting the usual ‘extension of protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

--

mwhiteside.dev · December 6, 2017, 7:52am

Ok thanks for your reply

Matt

···

On Dec 5, 2017, at 22:48, Jens Persson <jens@bitcycle.com> wrote:

It works for me with Xcode 9.1 and 9.2 using latest dev snapshot (from 2017-11-28 and 2017-12-03), I added -enable-experimental-conditional-conformances in Other Swift Flags as you show in the screenshot.
/Jens

On Wed, Dec 6, 2017 at 4:32 AM, Matt Whiteside via swift-users <swift-users@swift.org> wrote:
Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing the new '-enable-experimental-conditional-conformances' flag to Xcode? It works when I run swift from the command line, with the Dec. 5th snapshot toolchain, but not Xcode. I have tried whats in the screenshot below as well as adding -Xfrontend, but I’m still getting the usual ‘extension of protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

Jens · December 6, 2017, 8:24am

I've now installed 2017-12-05 snapshot and can confirm that it too works
for me.
In more detail:

1. Install swift-DEVELOPMENT-SNAPSHOT-2017-12-05-a-osx.pkg

2. Restart Xcode (I'm using Xcode 9.2 (9C40b))
(I guess it shouldn't be necessary to restart, but I think it might be
...)

3. Create a new command line project.

4. Put -enable-experimental-conditional-conformances in Other Swift Flags
in the project's Build Settings.

5. Enter the following code in main.swift and Build (which works without
errors):

protocol P {}
struct S<T> {}
extension S: P where T: P {}

Regarding step 2. I'm not 100% sure, but I think that it might be necessary
to restart Xcode after installing a new snapshot, because even if the new
snapshot can be selected from the toolchains menu, it doesn't take affect
until after restarting Xcode. I'm always restarting Xcode after installing
and selecting a new toolchain. Someone please correct me if you can prove
that this isn't necessary.

/Jens

···

On Wed, Dec 6, 2017 at 7:48 AM, Jens Persson via swift-users < swift-users@swift.org> wrote:

It works for me with Xcode 9.1 and 9.2 using latest dev snapshot (from
2017-11-28 and 2017-12-03), I added -enable-experimental-conditional-conformances
in Other Swift Flags as you show in the screenshot.
/Jens

On Wed, Dec 6, 2017 at 4:32 AM, Matt Whiteside via swift-users < > swift-users@swift.org> wrote:

Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing
the new '-enable-experimental-conditional-conformances' flag to Xcode?
It works when I run swift from the command line, with the Dec. 5th snapshot
toolchain, but not Xcode. I have tried whats in the screenshot below as
well as adding -Xfrontend, but I’m still getting the usual ‘extension of
protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

Jens · December 6, 2017, 8:25am

Oh I forgot to include the step where I select the newly installed
toolchain ...

···

On Wed, Dec 6, 2017 at 9:24 AM, Jens Persson via swift-users < swift-users@swift.org> wrote:

I've now installed 2017-12-05 snapshot and can confirm that it too works
for me.
In more detail:

1. Install swift-DEVELOPMENT-SNAPSHOT-2017-12-05-a-osx.pkg

2. Restart Xcode (I'm using Xcode 9.2 (9C40b))
(I guess it shouldn't be necessary to restart, but I think it might be
...)

3. Create a new command line project.

4. Put -enable-experimental-conditional-conformances in Other Swift Flags
in the project's Build Settings.

5. Enter the following code in main.swift and Build (which works without
errors):

protocol P {}
struct S<T> {}
extension S: P where T: P {}

Regarding step 2. I'm not 100% sure, but I think that it might be
necessary to restart Xcode after installing a new snapshot, because even if
the new snapshot can be selected from the toolchains menu, it doesn't take
affect until after restarting Xcode. I'm always restarting Xcode after
installing and selecting a new toolchain. Someone please correct me if you
can prove that this isn't necessary.

/Jens

On Wed, Dec 6, 2017 at 7:48 AM, Jens Persson via swift-users < > swift-users@swift.org> wrote:

It works for me with Xcode 9.1 and 9.2 using latest dev snapshot (from
2017-11-28 and 2017-12-03), I added -enable-experimental-conditional-conformances
in Other Swift Flags as you show in the screenshot.
/Jens

On Wed, Dec 6, 2017 at 4:32 AM, Matt Whiteside via swift-users < >> swift-users@swift.org> wrote:

Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing
the new '-enable-experimental-conditional-conformances' flag to Xcode?
It works when I run swift from the command line, with the Dec. 5th snapshot
toolchain, but not Xcode. I have tried whats in the screenshot below as
well as adding -Xfrontend, but I’m still getting the usual ‘extension of
protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

mwhiteside.dev · December 6, 2017, 3:35pm

Thanks Jens. Your example does work for me. The use case I have been trying to accomplish is conditional conformance of a protocol, not a struct. After re-reading, it looks like this is not covered by SE-0143.

import CoreGraphics

protocol Drawable {
func draw()
}

protocol Point2D{
  associatedtype T:FloatingPoint & ExpressibleByFloatLiteral
  var x:T{
    get
  }
  var y:T{
    get
  }
}

extension Collection: Drawable where Element:Point2D {//error: Extension of protocol ‘Collection’ cannot have an inheritance clause
  func draw(){
    print("drawing something here")
  }
}

Matt

···

On Dec 6, 2017, at 00:25, Jens Persson <jens@bitcycle.com> wrote:

Oh I forgot to include the step where I select the newly installed toolchain ...

On Wed, Dec 6, 2017 at 9:24 AM, Jens Persson via swift-users <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
I've now installed 2017-12-05 snapshot and can confirm that it too works for me.
In more detail:

1. Install swift-DEVELOPMENT-SNAPSHOT-2017-12-05-a-osx.pkg

2. Restart Xcode (I'm using Xcode 9.2 (9C40b))
(I guess it shouldn't be necessary to restart, but I think it might be ...)

3. Create a new command line project.

4. Put -enable-experimental-conditional-conformances in Other Swift Flags in the project's Build Settings.

5. Enter the following code in main.swift and Build (which works without errors):

protocol P {}
struct S<T> {}
extension S: P where T: P {}

Regarding step 2. I'm not 100% sure, but I think that it might be necessary to restart Xcode after installing a new snapshot, because even if the new snapshot can be selected from the toolchains menu, it doesn't take affect until after restarting Xcode. I'm always restarting Xcode after installing and selecting a new toolchain. Someone please correct me if you can prove that this isn't necessary.

/Jens

On Wed, Dec 6, 2017 at 7:48 AM, Jens Persson via swift-users <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
It works for me with Xcode 9.1 and 9.2 using latest dev snapshot (from 2017-11-28 and 2017-12-03), I added -enable-experimental-conditional-conformances in Other Swift Flags as you show in the screenshot.
/Jens

On Wed, Dec 6, 2017 at 4:32 AM, Matt Whiteside via swift-users <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing the new '-enable-experimental-conditional-conformances' flag to Xcode? It works when I run swift from the command line, with the Dec. 5th snapshot toolchain, but not Xcode. I have tried whats in the screenshot below as well as adding -Xfrontend, but I’m still getting the usual ‘extension of protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

<Screen Shot 2017-12-05 at 19.19.06.png>

_______________________________________________
swift-users mailing list
swift-users@swift.org <mailto:swift-users@swift.org>
https://lists.swift.org/mailman/listinfo/swift-users

_______________________________________________
swift-users mailing list
swift-users@swift.org <mailto:swift-users@swift.org>
https://lists.swift.org/mailman/listinfo/swift-users

_______________________________________________
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swift-users@swift.org <mailto:swift-users@swift.org>
https://lists.swift.org/mailman/listinfo/swift-users

mwhiteside.dev · December 6, 2017, 4:13pm

Looking into this a bit further, I see that this use case is specifically mentioned in the generics manifesto under the ‘unlikely' section.

<https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md#conditional-conformances-via-protocol-extensions> <https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md#conditional-conformances-via-protocol-extensions

···

On Dec 6, 2017, at 07:35, Matt Whiteside <mwhiteside.dev@gmail.com> wrote:

Thanks Jens. Your example does work for me. The use case I have been trying to accomplish is conditional conformance of a protocol, not a struct. After re-reading, it looks like this is not covered by SE-0143.

import CoreGraphics

protocol Drawable {
  func draw()
}

protocol Point2D{
  associatedtype T:FloatingPoint & ExpressibleByFloatLiteral
  var x:T{
    get
  }
  var y:T{
    get
  }
}

extension Collection: Drawable where Element:Point2D {//error: Extension of protocol ‘Collection’ cannot have an inheritance clause
  func draw(){
    print("drawing something here")
  }
}

Matt

On Dec 6, 2017, at 00:25, Jens Persson <jens@bitcycle.com <mailto:jens@bitcycle.com>> wrote:

Oh I forgot to include the step where I select the newly installed toolchain ...

On Wed, Dec 6, 2017 at 9:24 AM, Jens Persson via swift-users <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
I've now installed 2017-12-05 snapshot and can confirm that it too works for me.
In more detail:

1. Install swift-DEVELOPMENT-SNAPSHOT-2017-12-05-a-osx.pkg

2. Restart Xcode (I'm using Xcode 9.2 (9C40b))
    (I guess it shouldn't be necessary to restart, but I think it might be ...)

3. Create a new command line project.

4. Put -enable-experimental-conditional-conformances in Other Swift Flags in the project's Build Settings.

5. Enter the following code in main.swift and Build (which works without errors):

protocol P {}
struct S<T> {}
extension S: P where T: P {}

Regarding step 2. I'm not 100% sure, but I think that it might be necessary to restart Xcode after installing a new snapshot, because even if the new snapshot can be selected from the toolchains menu, it doesn't take affect until after restarting Xcode. I'm always restarting Xcode after installing and selecting a new toolchain. Someone please correct me if you can prove that this isn't necessary.

/Jens

On Wed, Dec 6, 2017 at 7:48 AM, Jens Persson via swift-users <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
It works for me with Xcode 9.1 and 9.2 using latest dev snapshot (from 2017-11-28 and 2017-12-03), I added -enable-experimental-conditional-conformances in Other Swift Flags as you show in the screenshot.
/Jens

On Wed, Dec 6, 2017 at 4:32 AM, Matt Whiteside via swift-users <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
Hello Swift Users,

[This is a resend with smaller attachment] Has anyone had luck passing the new '-enable-experimental-conditional-conformances' flag to Xcode? It works when I run swift from the command line, with the Dec. 5th snapshot toolchain, but not Xcode. I have tried whats in the screenshot below as well as adding -Xfrontend, but I’m still getting the usual ‘extension of protocol cannot have an inheritance clause’ error:

Thanks for any suggestions on this,

Matt

<Screen Shot 2017-12-05 at 19.19.06.png>

_______________________________________________
swift-users mailing list
swift-users@swift.org <mailto:swift-users@swift.org>
https://lists.swift.org/mailman/listinfo/swift-users

_______________________________________________
swift-users mailing list
swift-users@swift.org <mailto:swift-users@swift.org>
https://lists.swift.org/mailman/listinfo/swift-users

_______________________________________________
swift-users mailing list
swift-users@swift.org <mailto:swift-users@swift.org>
https://lists.swift.org/mailman/listinfo/swift-users