Re: [swift-users] Weird protocol behaviour.

2016-12-30 Thread Mikhail Seriukov via swift-users
So as the *foo(_ x:A) *function is generic, when we call *foo(x) *compiler
needs to determine what type is *A *to be able to create concrete function.
But x defined as *let x = X() as P *so we only know about it that it
conforms to *P *but not its real type to put instead of *A*. Right?
But where is the "Protocols do not conform to themselves" limitation is
coming out?

2016-12-30 18:25 GMT+07:00 Rien :

>
> > On 30 Dec 2016, at 12:14, Mikhail Seriukov via swift-users <
> swift-users@swift.org> wrote:
> >
> > Ok,
> > But I think I still do not get it.
> > What does really happen when we write this?
> >> let x = X() as P
> >>
>
> 'X()' creates a value.
> 'as P’ constrains the value such that the only things we know about it is
> that the value will conform to the protocol P
> ‘let x =‘ assigns the value to a constant, and the only thing we know
> about that constant is that we can call an operation of protocol P on it.
>
> Rien.
>
> > As I said, I expect x to be Any after that. If it is, then it should
> be ok IMO.
> > But if it is not then what is the actual type of x?
> >
> > So the real question is how the type checker works here?
> >
> >
> > 2016-12-25 22:13 GMT+07:00 Slava Pestov :
> >
> >> On Dec 22, 2016, at 4:43 PM, Howard Lovatt via swift-users <
> swift-users@swift.org> wrote:
> >>
> >> The following variation works:
> >>
> >> protocol P {}
> >>
> >> class P1:P {}
> >>
> >> class X:P1 {}
> >>
> >> func foo(_ x:A) {}
> >>
> >> func bar() {
> >> //let x = X() // this compiles
> >> let x = X() as P1 // this does not compile. Why?
> >> foo(x)
> >> }
> >>
> >> Which adds credence to the bug theory.
> >
> > It’s an intentional limitation. Protocols do not conform to themselves.
> Lifting the restriction would be difficult to do efficiently given our
> representation of generics and protocols at runtime.
> >
> > Slava
> >
> >>
> >> Note two changes: 1. two levels of inheritance and 2. change to
> classes. If you do two levels using protocols it doesn't work if you use
> either classes or structs.
> >>
> >>
> >>   -- Howard.
> >>
> >> On 23 December 2016 at 07:29, Kevin Nattinger 
> wrote:
> >> I recall seeing a request on the -evolution list for something like `T
> := X` to indicate it could be X itself or anything inheriting /
> implementing it, so it’s certainly known behavior, if not desired. IMO it’s
> a bug and `:` should be fixed to include the root type, whether or not that
> requires a discussion on -evolution.
> >>
> >>> On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users <
> swift-users@swift.org> wrote:
> >>>
> >>> I suspect a compiler bug since A is a P. The equivalent in Java works:
> >>>
> >>> interface P {}
> >>> class X implements P {}
> >>>
> >>>  void foo(A x) {}
> >>>
> >>> void bar() {
> >>> final P x = new X();
> >>> foo(x);
> >>> }
> >>>
> >>> -- Howard.
> >>>
> >>> On 23 Dec 2016, at 3:19 am, Rien via swift-users <
> swift-users@swift.org> wrote:
> >>>
>  IMO the error message says it all:
> 
>  Playground execution failed: error: MyPlayground8.playground:9:5:
> error: cannot invoke 'foo' with an argument list of type '(P)'
> foo(x)
> ^
> 
>  MyPlayground8.playground:9:5: note: expected an argument list of type
> '(A)'
> foo(x)
> ^
> 
>  I.e. you are passing in a protocol while the function is specified
> for a type.
>  Said other way: On which data do you expect the protocol to operate?
> 
>  Regards,
>  Rien
> 
>  Site: http://balancingrock.nl
>  Blog: http://swiftrien.blogspot.com
>  Github: http://github.com/Swiftrien
>  Project: http://swiftfire.nl
> 
> 
> 
> 
> > On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users <
> swift-users@swift.org> wrote:
> >
> > Hello community! I' wondering if somebody can explain this to me.
> > Please take look at the snippet.
> >
> > protocol P {}
> > struct X:P {}
> >
> > func foo(_ x:A) {}
> >
> > func bar() {
> >//let x = X() // this compiles
> >let x = X() as P // this does not compile. Why?
> >foo(x)
> > }
> >
> > I expect the both cases to work though. But only first works? And I
> do not understand why.
> > My coworkers said that it is a compiler bug, but I'm not shure it is.
> > Thanks for the help.
> > ___
> > 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
> >>
> >>
> >> 

Re: [swift-users] Weird protocol behaviour.

2016-12-30 Thread Rien via swift-users

> On 30 Dec 2016, at 12:14, Mikhail Seriukov via swift-users 
>  wrote:
> 
> Ok, 
> But I think I still do not get it.
> What does really happen when we write this?
>> let x = X() as P
>> 

'X()' creates a value.
'as P’ constrains the value such that the only things we know about it is that 
the value will conform to the protocol P
‘let x =‘ assigns the value to a constant, and the only thing we know about 
that constant is that we can call an operation of protocol P on it.

Rien.

> As I said, I expect x to be Any after that. If it is, then it should be ok 
> IMO.
> But if it is not then what is the actual type of x? 
> 
> So the real question is how the type checker works here?
> 
> 
> 2016-12-25 22:13 GMT+07:00 Slava Pestov :
> 
>> On Dec 22, 2016, at 4:43 PM, Howard Lovatt via swift-users 
>>  wrote:
>> 
>> The following variation works:
>> 
>> protocol P {}
>> 
>> class P1:P {}
>> 
>> class X:P1 {}
>> 
>> func foo(_ x:A) {}
>> 
>> func bar() {
>> //let x = X() // this compiles
>> let x = X() as P1 // this does not compile. Why?
>> foo(x)
>> }
>> 
>> Which adds credence to the bug theory.
> 
> It’s an intentional limitation. Protocols do not conform to themselves. 
> Lifting the restriction would be difficult to do efficiently given our 
> representation of generics and protocols at runtime.
> 
> Slava
> 
>> 
>> Note two changes: 1. two levels of inheritance and 2. change to classes. If 
>> you do two levels using protocols it doesn't work if you use either classes 
>> or structs.
>> 
>> 
>>   -- Howard.
>> 
>> On 23 December 2016 at 07:29, Kevin Nattinger  wrote:
>> I recall seeing a request on the -evolution list for something like `T := X` 
>> to indicate it could be X itself or anything inheriting / implementing it, 
>> so it’s certainly known behavior, if not desired. IMO it’s a bug and `:` 
>> should be fixed to include the root type, whether or not that requires a 
>> discussion on -evolution.
>> 
>>> On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users 
>>>  wrote:
>>> 
>>> I suspect a compiler bug since A is a P. The equivalent in Java works:
>>> 
>>> interface P {}
>>> class X implements P {}
>>>  
>>>  void foo(A x) {}
>>>  
>>> void bar() {
>>> final P x = new X();
>>> foo(x);
>>> }
>>> 
>>> -- Howard. 
>>> 
>>> On 23 Dec 2016, at 3:19 am, Rien via swift-users  
>>> wrote:
>>> 
 IMO the error message says it all:
 
 Playground execution failed: error: MyPlayground8.playground:9:5: error: 
 cannot invoke 'foo' with an argument list of type '(P)'
foo(x)
^
 
 MyPlayground8.playground:9:5: note: expected an argument list of type '(A)'
foo(x)
^
 
 I.e. you are passing in a protocol while the function is specified for a 
 type.
 Said other way: On which data do you expect the protocol to operate?
 
 Regards,
 Rien
 
 Site: http://balancingrock.nl
 Blog: http://swiftrien.blogspot.com
 Github: http://github.com/Swiftrien
 Project: http://swiftfire.nl
 
 
 
 
> On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users 
>  wrote:
> 
> Hello community! I' wondering if somebody can explain this to me.
> Please take look at the snippet.
> 
> protocol P {}
> struct X:P {}
> 
> func foo(_ x:A) {}
> 
> func bar() {
>//let x = X() // this compiles
>let x = X() as P // this does not compile. Why?
>foo(x)
> }
> 
> I expect the both cases to work though. But only first works? And I do 
> not understand why.
> My coworkers said that it is a compiler bug, but I'm not shure it is.
> Thanks for the help.
> ___
> 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
>> 
>> 
>> ___
>> swift-users mailing list
>> swift-users@swift.org
>> https://lists.swift.org/mailman/listinfo/swift-users
> 
> 
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> https://lists.swift.org/mailman/listinfo/swift-users

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Re: [swift-users] Weird protocol behaviour.

2016-12-30 Thread Mikhail Seriukov via swift-users
Ok,
But I think I still do not get it.
What does really happen when we write this?

let x = X() as P

As I said, I expect x to be Any after that. If it is, then it should be
ok IMO.
But if it is not then what is the actual type of x?

So the real question is how the type checker works here?


2016-12-25 22:13 GMT+07:00 Slava Pestov :

>
> On Dec 22, 2016, at 4:43 PM, Howard Lovatt via swift-users <
> swift-users@swift.org> wrote:
>
> The following variation works:
>
> protocol P {}
>
> class P1:P {}
>
> class X:P1 {}
>
> func foo(_ x:A) {}
>
> func bar() {
> //let x = X() // this compiles
> let x = X() as P1 // this does not compile. Why?
> foo(x)
> }
>
> Which adds credence to the bug theory.
>
>
> It’s an intentional limitation. Protocols do not conform to themselves.
> Lifting the restriction would be difficult to do efficiently given our
> representation of generics and protocols at runtime.
>
> Slava
>
>
> Note two changes: 1. two levels of inheritance and 2. change to classes.
> If you do two levels using protocols it doesn't work if you use either
> classes or structs.
>
>
>   -- Howard.
>
> On 23 December 2016 at 07:29, Kevin Nattinger  wrote:
>
>> I recall seeing a request on the -evolution list for something like `T :=
>> X` to indicate it could be X itself or anything inheriting / implementing
>> it, so it’s certainly known behavior, if not desired. IMO it’s a bug and
>> `:` should be fixed to include the root type, whether or not that requires
>> a discussion on -evolution.
>>
>> On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users <
>> swift-users@swift.org> wrote:
>>
>> I suspect a compiler bug since A is a P. The equivalent in Java works:
>>
>> interface P {}
>> class X implements P {}
>>
>>  void foo(A x) {}
>>
>> void bar() {
>> final P x = new X();
>> foo(x);
>> }
>>
>> -- Howard.
>>
>> On 23 Dec 2016, at 3:19 am, Rien via swift-users 
>> wrote:
>>
>> IMO the error message says it all:
>>
>> Playground execution failed: error: MyPlayground8.playground:9:5: error:
>> cannot invoke 'foo' with an argument list of type '(P)'
>>foo(x)
>>^
>>
>> MyPlayground8.playground:9:5: note: expected an argument list of type
>> '(A)'
>>foo(x)
>>^
>>
>> I.e. you are passing in a protocol while the function is specified for a
>> type.
>> Said other way: On which data do you expect the protocol to operate?
>>
>> Regards,
>> Rien
>>
>> Site: http://balancingrock.nl
>> Blog: http://swiftrien.blogspot.com
>> Github: http://github.com/Swiftrien
>> Project: http://swiftfire.nl
>>
>>
>>
>>
>> On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users <
>> swift-users@swift.org> wrote:
>>
>>
>> Hello community! I' wondering if somebody can explain this to me.
>>
>> Please take look at the snippet.
>>
>>
>> protocol P {}
>>
>> struct X:P {}
>>
>>
>> func foo(_ x:A) {}
>>
>>
>> func bar() {
>>
>>//let x = X() // this compiles
>>
>>let x = X() as P // this does not compile. Why?
>>
>>foo(x)
>>
>> }
>>
>>
>> I expect the both cases to work though. But only first works? And I do
>> not understand why.
>>
>> My coworkers said that it is a compiler bug, but I'm not shure it is.
>>
>> Thanks for the help.
>>
>> ___
>>
>> 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
>>
>>
>>
> ___
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> swift-users@swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
>
>
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Re: [swift-users] Weird protocol behaviour.

2016-12-25 Thread Slava Pestov via swift-users

> On Dec 22, 2016, at 4:43 PM, Howard Lovatt via swift-users 
>  wrote:
> 
> The following variation works:
> 
> protocol P {}
> 
> class P1:P {}
> 
> class X:P1 {}
> 
> func foo(_ x:A) {}
> 
> func bar() {
> //let x = X() // this compiles
> let x = X() as P1 // this does not compile. Why?
> foo(x)
> }
> 
> Which adds credence to the bug theory.

It’s an intentional limitation. Protocols do not conform to themselves. Lifting 
the restriction would be difficult to do efficiently given our representation 
of generics and protocols at runtime.

Slava

> 
> Note two changes: 1. two levels of inheritance and 2. change to classes. If 
> you do two levels using protocols it doesn't work if you use either classes 
> or structs.
> 
> 
>   -- Howard.
> 
> On 23 December 2016 at 07:29, Kevin Nattinger  > wrote:
> I recall seeing a request on the -evolution list for something like `T := X` 
> to indicate it could be X itself or anything inheriting / implementing it, so 
> it’s certainly known behavior, if not desired. IMO it’s a bug and `:` should 
> be fixed to include the root type, whether or not that requires a discussion 
> on -evolution.
> 
>> On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users 
>> > wrote:
>> 
>> I suspect a compiler bug since A is a P. The equivalent in Java works:
>> 
>> interface P {}
>> class X implements P {}
>>  
>>  void foo(A x) {}
>>  
>> void bar() {
>> final P x = new X();
>> foo(x);
>> }
>> 
>> -- Howard. 
>> 
>> On 23 Dec 2016, at 3:19 am, Rien via swift-users > > wrote:
>> 
>>> IMO the error message says it all:
>>> 
>>> Playground execution failed: error: MyPlayground8.playground:9:5: error: 
>>> cannot invoke 'foo' with an argument list of type '(P)'
>>>foo(x)
>>>^
>>> 
>>> MyPlayground8.playground:9:5: note: expected an argument list of type '(A)'
>>>foo(x)
>>>^
>>> 
>>> I.e. you are passing in a protocol while the function is specified for a 
>>> type.
>>> Said other way: On which data do you expect the protocol to operate?
>>> 
>>> Regards,
>>> Rien
>>> 
>>> Site: http://balancingrock.nl 
>>> Blog: http://swiftrien.blogspot.com 
>>> Github: http://github.com/Swiftrien 
>>> Project: http://swiftfire.nl 
>>> 
>>> 
>>> 
>>> 
 On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users 
 > wrote:
 
 Hello community! I' wondering if somebody can explain this to me.
 Please take look at the snippet.
 
 protocol P {}
 struct X:P {}
 
 func foo(_ x:A) {}
 
 func bar() {
//let x = X() // this compiles
let x = X() as P // this does not compile. Why?
foo(x)
 }
 
 I expect the both cases to work though. But only first works? And I do not 
 understand why.
 My coworkers said that it is a compiler bug, but I'm not shure it is.
 Thanks for the help.
 ___
 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 
>> 
> 
> 
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Re: [swift-users] Weird protocol behaviour.

2016-12-23 Thread Zhao Xin via swift-users
My previous theory was wrong.

> P is an existential for x: P = … where it is upgraded to the static P in foo

Why it needs to be upgraded? Why not just use `P` as a protocol instead of
a `type`? Xcode error message calls `P` as a type.


Zhaoxin

On Fri, Dec 23, 2016 at 9:03 PM, Adrian Zubarev <
adrian.zuba...@devandartist.com> wrote:

> I’m not sure what you mean. P is an existential for x: P = … where it is
> upgraded to the static P in foo, but the static P does not conform
> to the existential P, which results in an error described by the OP.
>
> x: P = … here it’s Any any type that conforms to P. Any is a type
> of it’s own, and when existentials will be implemented I’d assume that
> there won’t be any upgrade to P from generic context.
>
> let x: Any = …
>
> foo(x)
> // A == Any which should make foo equivalent to
> // `func foo(_ x: Any)` or the current `func foo(_ x: P)`
>
> Right now we just cannot be explicit about existentials.
>
> Please correct me if I’m wrong. ;)
>
>
>
> --
> Adrian Zubarev
> Sent with Airmail
>
> Am 23. Dezember 2016 um 13:47:18, Zhao Xin (owe...@gmail.com) schrieb:
>
> You mis-labelled you problem in your original email.
>
> let x = X() as P // this does not compile. Why?
> foo(x)
>
> The issue is not in line ` let x = X() as P`. It is in line ` foo(x)`,
> `x's type is P`, but `foo(:)` request a parameter type of `A`, not `P`.
>
> `func foo(_ x:A) {}` means, `x` must be `A`, and `A` conforms `P`.
> But not all `P`s are `A`.
>
> Zhaoxin
>
> On Fri, Dec 23, 2016 at 5:26 PM, Adrian Zubarev via swift-users <
> swift-users@swift.org> wrote:
>
>> Whoops, wait a second. Correcting my self here. Copied the wrong url.
>>
>> Here is the proposal I meant. LINK
>> 
>>
>>
>> --
>> Adrian Zubarev
>> Sent with Airmail
>>
>> Am 23. Dezember 2016 um 09:57:49, Adrian Zubarev (
>> adrian.zuba...@devandartist.com) schrieb:
>>
>>
>>-
>>
>>What are you trying to solve here?
>>-
>>
>>Do you heavily rely on what A can be?
>>-
>>
>>Can’t you just write func foo(_ x: P) {} (here P is an *existential*
>>like [in some future] Any)?!
>>-
>>
>>AnyObject is for classes, but you’d get the same result changing X to
>>a class ;)
>>
>> If you want scratch the surface of what happens to protocols in a generic
>> context, you could read our proposal about meta types here
>> 
>> .
>>
>>
>> --
>> Adrian Zubarev
>> Sent with Airmail
>>
>> Am 23. Dezember 2016 um 09:43:34, Mikhail Seriukov via swift-users (
>> swift-users@swift.org) schrieb:
>>
>> No it does not.
>>> You have made a type out of the parameter. It’s no longer a protocol.
>>> IMO the failure here is to understand the difference between a type and
>>> a protocol.
>>> A type (even if empty) is always a combination of storage with functions
>>> (that are assumed to work on the data in storage)
>>> A protocol is just a definition of functions without the accompanying
>>> data.
>>>
>>
>> I see your point.
>> But actually when I write it as  `let x = X() as P` I really mean that I
>> want `x` to be `AnyObject` but conforming to P, not just protocol itself.
>> Is it even possible to downcast it this way?
>>
>> 2016-12-23 14:51 GMT+07:00 Marinus van der Lugt :
>>
>>>
>>> On 22 Dec 2016, at 22:43, Howard Lovatt  wrote:
>>>
>>> The following variation works:
>>>
>>> protocol P {}
>>>
>>> class P1:P {}
>>>
>>> class X:P1 {}
>>>
>>> func foo(_ x:A) {}
>>>
>>> func bar() {
>>> //let x = X() // this compiles
>>> let x = X() as P1 // this does not compile. Why?
>>> foo(x)
>>> }
>>>
>>> Which adds credence to the bug theory.
>>>
>>>
>>>
>>> No it does not.
>>> You have made a type out of the parameter. It’s no longer a protocol.
>>> IMO the failure here is to understand the difference between a type and
>>> a protocol.
>>> A type (even if empty) is always a combination of storage with functions
>>> (that are assumed to work on the data in storage)
>>> A protocol is just a definition of functions without the accompanying
>>> data.
>>>
>>> Rien.
>>>
>>>
>>>
>>>
>>> Note two changes: 1. two levels of inheritance and 2. change to classes.
>>> If you do two levels using protocols it doesn't work if you use either
>>> classes or structs.
>>>
>>>
>>>   -- Howard.
>>>
>>> On 23 December 2016 at 07:29, Kevin Nattinger 
>>> wrote:
>>>
 I recall seeing a request on the -evolution list for something like `T
 := X` to indicate it could be X itself or anything inheriting /
 implementing it, so it’s certainly known behavior, if not desired. IMO it’s
 a bug and `:` should be fixed to include the root type, whether or not that
 requires a discussion on 

Re: [swift-users] Weird protocol behaviour.

2016-12-23 Thread Adrian Zubarev via swift-users
I’m not sure what you mean. P is an existential for x: P = … where it is 
upgraded to the static P in foo, but the static P does not conform to 
the existential P, which results in an error described by the OP.

x: P = … here it’s Any any type that conforms to P. Any is a type of it’s 
own, and when existentials will be implemented I’d assume that there won’t be 
any upgrade to P from generic context.

let x: Any = …

foo(x)  
// A == Any which should make foo equivalent to  
// `func foo(_ x: Any)` or the current `func foo(_ x: P)`
Right now we just cannot be explicit about existentials.

Please correct me if I’m wrong. ;)



-- 
Adrian Zubarev
Sent with Airmail

Am 23. Dezember 2016 um 13:47:18, Zhao Xin (owe...@gmail.com) schrieb:

You mis-labelled you problem in your original email.

    let x = X() as P // this does not compile. Why?
    foo(x)

The issue is not in line ` let x = X() as P`. It is in line ` foo(x)`, `x's 
type is P`, but `foo(:)` request a parameter type of `A`, not `P`.

`func foo(_ x:A) {}` means, `x` must be `A`, and `A` conforms `P`. But not 
all `P`s are `A`.

Zhaoxin

On Fri, Dec 23, 2016 at 5:26 PM, Adrian Zubarev via swift-users 
 wrote:
Whoops, wait a second. Correcting my self here. Copied the wrong url.

Here is the proposal I meant. LINK



-- 
Adrian Zubarev
Sent with Airmail

Am 23. Dezember 2016 um 09:57:49, Adrian Zubarev 
(adrian.zuba...@devandartist.com) schrieb:

What are you trying to solve here?

Do you heavily rely on what A can be?

Can’t you just write func foo(_ x: P) {} (here P is an existential like [in 
some future] Any)?!

AnyObject is for classes, but you’d get the same result changing X to a class ;)

If you want scratch the surface of what happens to protocols in a generic 
context, you could read our proposal about meta types here.



-- 
Adrian Zubarev
Sent with Airmail

Am 23. Dezember 2016 um 09:43:34, Mikhail Seriukov via swift-users 
(swift-users@swift.org) schrieb:

No it does not.
You have made a type out of the parameter. It’s no longer a protocol.
IMO the failure here is to understand the difference between a type and a 
protocol.
A type (even if empty) is always a combination of storage with functions (that 
are assumed to work on the data in storage)
A protocol is just a definition of functions without the accompanying data.

I see your point. 
But actually when I write it as  `let x = X() as P` I really mean that I want 
`x` to be `AnyObject` but conforming to P, not just protocol itself.
Is it even possible to downcast it this way?

2016-12-23 14:51 GMT+07:00 Marinus van der Lugt :

On 22 Dec 2016, at 22:43, Howard Lovatt  wrote:

The following variation works:

protocol P {}

class P1:P {}

class X:P1 {}

func foo(_ x:A) {}

func bar() {
    //let x = X() // this compiles
    let x = X() as P1 // this does not compile. Why?
    foo(x)
}

Which adds credence to the bug theory.


No it does not.
You have made a type out of the parameter. It’s no longer a protocol.
IMO the failure here is to understand the difference between a type and a 
protocol.
A type (even if empty) is always a combination of storage with functions (that 
are assumed to work on the data in storage)
A protocol is just a definition of functions without the accompanying data.

Rien.




Note two changes: 1. two levels of inheritance and 2. change to classes. If you 
do two levels using protocols it doesn't work if you use either classes or 
structs.


  -- Howard.

On 23 December 2016 at 07:29, Kevin Nattinger  wrote:
I recall seeing a request on the -evolution list for something like `T := X` to 
indicate it could be X itself or anything inheriting / implementing it, so it’s 
certainly known behavior, if not desired. IMO it’s a bug and `:` should be 
fixed to include the root type, whether or not that requires a discussion on 
-evolution.

On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users 
 wrote:

I suspect a compiler bug since A is a P. The equivalent in Java works:

interface P {}
class X implements P {}
 
 void foo(A x) {}
 
void bar() {
    final P x = new X();
    foo(x);
}

-- Howard. 

On 23 Dec 2016, at 3:19 am, Rien via swift-users  wrote:

IMO the error message says it all:

Playground execution failed: error: MyPlayground8.playground:9:5: error: cannot 
invoke 'foo' with an argument list of type '(P)'
   foo(x)
   ^

MyPlayground8.playground:9:5: note: expected an argument list of type '(A)'
   foo(x)
   ^

I.e. you are passing in a protocol while the function is specified for a type.
Said other way: On which data do you expect the protocol to operate?

Regards,
Rien

Site: http://balancingrock.nl
Blog: http://swiftrien.blogspot.com
Github: http://github.com/Swiftrien
Project: http://swiftfire.nl




On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users 
 wrote:

Hello community! I' 

Re: [swift-users] Weird protocol behaviour.

2016-12-23 Thread Adrian Zubarev via swift-users
I assume when we get existentials, your problem could be solved like this:

protocol P {}
class X: P {}

func foo(_ x:A) {}

func bar() {
let x = X() as Any
foo(x)
}
Here A will be Any which conforms to P and makes the compiler happy.

let c: P = … here is P and existential like (future) Any.
x as P here is P used as a type.
It’s weird that the latter is a type but the first example is an existential. I 
think this is a design choice, because we almost never need the protocol as a 
type.



-- 
Adrian Zubarev
Sent with Airmail

Am 23. Dezember 2016 um 09:57:49, Adrian Zubarev 
(adrian.zuba...@devandartist.com) schrieb:

What are you trying to solve here?

Do you heavily rely on what A can be?

Can’t you just write func foo(_ x: P) {} (here P is an existential like [in 
some future] Any)?!

AnyObject is for classes, but you’d get the same result changing X to a class ;)

If you want scratch the surface of what happens to protocols in a generic 
context, you could read our proposal about meta types here.



-- 
Adrian Zubarev
Sent with Airmail

Am 23. Dezember 2016 um 09:43:34, Mikhail Seriukov via swift-users 
(swift-users@swift.org) schrieb:

No it does not.
You have made a type out of the parameter. It’s no longer a protocol.
IMO the failure here is to understand the difference between a type and a 
protocol.
A type (even if empty) is always a combination of storage with functions (that 
are assumed to work on the data in storage)
A protocol is just a definition of functions without the accompanying data.

I see your point. 
But actually when I write it as  `let x = X() as P` I really mean that I want 
`x` to be `AnyObject` but conforming to P, not just protocol itself.
Is it even possible to downcast it this way?

2016-12-23 14:51 GMT+07:00 Marinus van der Lugt :

On 22 Dec 2016, at 22:43, Howard Lovatt  wrote:

The following variation works:

protocol P {}

class P1:P {}

class X:P1 {}

func foo(_ x:A) {}

func bar() {
    //let x = X() // this compiles
    let x = X() as P1 // this does not compile. Why?
    foo(x)
}

Which adds credence to the bug theory.


No it does not.
You have made a type out of the parameter. It’s no longer a protocol.
IMO the failure here is to understand the difference between a type and a 
protocol.
A type (even if empty) is always a combination of storage with functions (that 
are assumed to work on the data in storage)
A protocol is just a definition of functions without the accompanying data.

Rien.




Note two changes: 1. two levels of inheritance and 2. change to classes. If you 
do two levels using protocols it doesn't work if you use either classes or 
structs.


  -- Howard.

On 23 December 2016 at 07:29, Kevin Nattinger  wrote:
I recall seeing a request on the -evolution list for something like `T := X` to 
indicate it could be X itself or anything inheriting / implementing it, so it’s 
certainly known behavior, if not desired. IMO it’s a bug and `:` should be 
fixed to include the root type, whether or not that requires a discussion on 
-evolution.

On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users 
 wrote:

I suspect a compiler bug since A is a P. The equivalent in Java works:

interface P {}
class X implements P {}
 
 void foo(A x) {}
 
void bar() {
    final P x = new X();
    foo(x);
}

-- Howard. 

On 23 Dec 2016, at 3:19 am, Rien via swift-users  wrote:

IMO the error message says it all:

Playground execution failed: error: MyPlayground8.playground:9:5: error: cannot 
invoke 'foo' with an argument list of type '(P)'
   foo(x)
   ^

MyPlayground8.playground:9:5: note: expected an argument list of type '(A)'
   foo(x)
   ^

I.e. you are passing in a protocol while the function is specified for a type.
Said other way: On which data do you expect the protocol to operate?

Regards,
Rien

Site: http://balancingrock.nl
Blog: http://swiftrien.blogspot.com
Github: http://github.com/Swiftrien
Project: http://swiftfire.nl




On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users 
 wrote:

Hello community! I' wondering if somebody can explain this to me.
Please take look at the snippet.

protocol P {}
struct X:P {}

func foo(_ x:A) {}

func bar() {
   //let x = X() // this compiles
   let x = X() as P // this does not compile. Why?
   foo(x)
}

I expect the both cases to work though. But only first works? And I do not 
understand why.
My coworkers said that it is a compiler bug, but I'm not shure it is.
Thanks for the help.
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Re: [swift-users] Weird protocol behaviour.

2016-12-23 Thread Rien via swift-users

> On 23 Dec 2016, at 09:43, Mikhail Seriukov  wrote:
> 
> No it does not.
> You have made a type out of the parameter. It’s no longer a protocol.
> IMO the failure here is to understand the difference between a type and a 
> protocol.
> A type (even if empty) is always a combination of storage with functions 
> (that are assumed to work on the data in storage)
> A protocol is just a definition of functions without the accompanying data.
> 
> I see your point. 
> But actually when I write it as  `let x = X() as P` I really mean that I want 
> `x` to be `AnyObject` but conforming to P, not just protocol itself.
> Is it even possible to downcast it this way?

Yes, but only for a destination that needs a protocol. Not for a destination 
that needs a type.

I.e. in the example

protocol P {}
struct X:P {}

func foo(_ x:A) {}

func bar(_ x:P) {}

func bar() {
var p: P
//let x = X() // this compiles
let x = X() as P // this does not compile. Why?
p = x
bar(p)
}

Regards,
Rien.

> 
> 2016-12-23 14:51 GMT+07:00 Marinus van der Lugt :
> 
>> On 22 Dec 2016, at 22:43, Howard Lovatt  wrote:
>> 
>> The following variation works:
>> 
>> protocol P {}
>> 
>> class P1:P {}
>> 
>> class X:P1 {}
>> 
>> func foo(_ x:A) {}
>> 
>> func bar() {
>> //let x = X() // this compiles
>> let x = X() as P1 // this does not compile. Why?
>> foo(x)
>> }
>> 
>> Which adds credence to the bug theory.
> 
> 
> No it does not.
> You have made a type out of the parameter. It’s no longer a protocol.
> IMO the failure here is to understand the difference between a type and a 
> protocol.
> A type (even if empty) is always a combination of storage with functions 
> (that are assumed to work on the data in storage)
> A protocol is just a definition of functions without the accompanying data.
> 
> Rien.
> 
> 
> 
>> 
>> Note two changes: 1. two levels of inheritance and 2. change to classes. If 
>> you do two levels using protocols it doesn't work if you use either classes 
>> or structs.
>> 
>> 
>>   -- Howard.
>> 
>> On 23 December 2016 at 07:29, Kevin Nattinger  wrote:
>> I recall seeing a request on the -evolution list for something like `T := X` 
>> to indicate it could be X itself or anything inheriting / implementing it, 
>> so it’s certainly known behavior, if not desired. IMO it’s a bug and `:` 
>> should be fixed to include the root type, whether or not that requires a 
>> discussion on -evolution.
>> 
>>> On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users 
>>>  wrote:
>>> 
>>> I suspect a compiler bug since A is a P. The equivalent in Java works:
>>> 
>>> interface P {}
>>> class X implements P {}
>>>  
>>>  void foo(A x) {}
>>>  
>>> void bar() {
>>> final P x = new X();
>>> foo(x);
>>> }
>>> 
>>> -- Howard. 
>>> 
>>> On 23 Dec 2016, at 3:19 am, Rien via swift-users  
>>> wrote:
>>> 
 IMO the error message says it all:
 
 Playground execution failed: error: MyPlayground8.playground:9:5: error: 
 cannot invoke 'foo' with an argument list of type '(P)'
foo(x)
^
 
 MyPlayground8.playground:9:5: note: expected an argument list of type '(A)'
foo(x)
^
 
 I.e. you are passing in a protocol while the function is specified for a 
 type.
 Said other way: On which data do you expect the protocol to operate?
 
 Regards,
 Rien
 
 Site: http://balancingrock.nl
 Blog: http://swiftrien.blogspot.com
 Github: http://github.com/Swiftrien
 Project: http://swiftfire.nl
 
 
 
 
> On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users 
>  wrote:
> 
> Hello community! I' wondering if somebody can explain this to me.
> Please take look at the snippet.
> 
> protocol P {}
> struct X:P {}
> 
> func foo(_ x:A) {}
> 
> func bar() {
>//let x = X() // this compiles
>let x = X() as P // this does not compile. Why?
>foo(x)
> }
> 
> I expect the both cases to work though. But only first works? And I do 
> not understand why.
> My coworkers said that it is a compiler bug, but I'm not shure it is.
> Thanks for the help.
> ___
> 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
>> 
>> 
> 
> 

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Re: [swift-users] Weird protocol behaviour.

2016-12-23 Thread Adrian Zubarev via swift-users
What are you trying to solve here?

Do you heavily rely on what A can be?

Can’t you just write func foo(_ x: P) {} (here P is an existential like [in 
some future] Any)?!

AnyObject is for classes, but you’d get the same result changing X to a class ;)

If you want scratch the surface of what happens to protocols in a generic 
context, you could read our proposal about meta types here.



-- 
Adrian Zubarev
Sent with Airmail

Am 23. Dezember 2016 um 09:43:34, Mikhail Seriukov via swift-users 
(swift-users@swift.org) schrieb:

No it does not.
You have made a type out of the parameter. It’s no longer a protocol.
IMO the failure here is to understand the difference between a type and a 
protocol.
A type (even if empty) is always a combination of storage with functions (that 
are assumed to work on the data in storage)
A protocol is just a definition of functions without the accompanying data.

I see your point. 
But actually when I write it as  `let x = X() as P` I really mean that I want 
`x` to be `AnyObject` but conforming to P, not just protocol itself.
Is it even possible to downcast it this way?

2016-12-23 14:51 GMT+07:00 Marinus van der Lugt :

On 22 Dec 2016, at 22:43, Howard Lovatt  wrote:

The following variation works:

protocol P {}

class P1:P {}

class X:P1 {}

func foo(_ x:A) {}

func bar() {
    //let x = X() // this compiles
    let x = X() as P1 // this does not compile. Why?
    foo(x)
}

Which adds credence to the bug theory.


No it does not.
You have made a type out of the parameter. It’s no longer a protocol.
IMO the failure here is to understand the difference between a type and a 
protocol.
A type (even if empty) is always a combination of storage with functions (that 
are assumed to work on the data in storage)
A protocol is just a definition of functions without the accompanying data.

Rien.




Note two changes: 1. two levels of inheritance and 2. change to classes. If you 
do two levels using protocols it doesn't work if you use either classes or 
structs.


  -- Howard.

On 23 December 2016 at 07:29, Kevin Nattinger  wrote:
I recall seeing a request on the -evolution list for something like `T := X` to 
indicate it could be X itself or anything inheriting / implementing it, so it’s 
certainly known behavior, if not desired. IMO it’s a bug and `:` should be 
fixed to include the root type, whether or not that requires a discussion on 
-evolution.  

On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users 
 wrote:

I suspect a compiler bug since A is a P. The equivalent in Java works:

interface P {}
class X implements P {}
 
 void foo(A x) {}
 
void bar() {
    final P x = new X();
    foo(x);
}

-- Howard. 

On 23 Dec 2016, at 3:19 am, Rien via swift-users  wrote:

IMO the error message says it all:

Playground execution failed: error: MyPlayground8.playground:9:5: error: cannot 
invoke 'foo' with an argument list of type '(P)'
   foo(x)
   ^

MyPlayground8.playground:9:5: note: expected an argument list of type '(A)'
   foo(x)
   ^

I.e. you are passing in a protocol while the function is specified for a type.
Said other way: On which data do you expect the protocol to operate?

Regards,
Rien

Site: http://balancingrock.nl
Blog: http://swiftrien.blogspot.com
Github: http://github.com/Swiftrien
Project: http://swiftfire.nl




On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users 
 wrote:

Hello community! I' wondering if somebody can explain this to me.
Please take look at the snippet.

protocol P {}
struct X:P {}

func foo(_ x:A) {}

func bar() {
   //let x = X() // this compiles
   let x = X() as P // this does not compile. Why?
   foo(x)
}

I expect the both cases to work though. But only first works? And I do not 
understand why.
My coworkers said that it is a compiler bug, but I'm not shure it is.
Thanks for the help.
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Re: [swift-users] Weird protocol behaviour.

2016-12-23 Thread Mikhail Seriukov via swift-users
>
> No it does not.
> You have made a type out of the parameter. It’s no longer a protocol.
> IMO the failure here is to understand the difference between a type and a
> protocol.
> A type (even if empty) is always a combination of storage with functions
> (that are assumed to work on the data in storage)
> A protocol is just a definition of functions without the accompanying data.
>

I see your point.
But actually when I write it as  `let x = X() as P` I really mean that I
want `x` to be `AnyObject` but conforming to P, not just protocol itself.
Is it even possible to downcast it this way?

2016-12-23 14:51 GMT+07:00 Marinus van der Lugt :

>
> On 22 Dec 2016, at 22:43, Howard Lovatt  wrote:
>
> The following variation works:
>
> protocol P {}
>
> class P1:P {}
>
> class X:P1 {}
>
> func foo(_ x:A) {}
>
> func bar() {
> //let x = X() // this compiles
> let x = X() as P1 // this does not compile. Why?
> foo(x)
> }
>
> Which adds credence to the bug theory.
>
>
>
> No it does not.
> You have made a type out of the parameter. It’s no longer a protocol.
> IMO the failure here is to understand the difference between a type and a
> protocol.
> A type (even if empty) is always a combination of storage with functions
> (that are assumed to work on the data in storage)
> A protocol is just a definition of functions without the accompanying data.
>
> Rien.
>
>
>
>
> Note two changes: 1. two levels of inheritance and 2. change to classes.
> If you do two levels using protocols it doesn't work if you use either
> classes or structs.
>
>
>   -- Howard.
>
> On 23 December 2016 at 07:29, Kevin Nattinger  wrote:
>
>> I recall seeing a request on the -evolution list for something like `T :=
>> X` to indicate it could be X itself or anything inheriting / implementing
>> it, so it’s certainly known behavior, if not desired. IMO it’s a bug and
>> `:` should be fixed to include the root type, whether or not that requires
>> a discussion on -evolution.
>>
>> On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users <
>> swift-users@swift.org> wrote:
>>
>> I suspect a compiler bug since A is a P. The equivalent in Java works:
>>
>> interface P {}
>> class X implements P {}
>>
>>  void foo(A x) {}
>>
>> void bar() {
>> final P x = new X();
>> foo(x);
>> }
>>
>> -- Howard.
>>
>> On 23 Dec 2016, at 3:19 am, Rien via swift-users 
>> wrote:
>>
>> IMO the error message says it all:
>>
>> Playground execution failed: error: MyPlayground8.playground:9:5: error:
>> cannot invoke 'foo' with an argument list of type '(P)'
>>foo(x)
>>^
>>
>> MyPlayground8.playground:9:5: note: expected an argument list of type
>> '(A)'
>>foo(x)
>>^
>>
>> I.e. you are passing in a protocol while the function is specified for a
>> type.
>> Said other way: On which data do you expect the protocol to operate?
>>
>> Regards,
>> Rien
>>
>> Site: http://balancingrock.nl
>> Blog: http://swiftrien.blogspot.com
>> Github: http://github.com/Swiftrien
>> Project: http://swiftfire.nl
>>
>>
>>
>>
>> On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users <
>> swift-users@swift.org> wrote:
>>
>>
>> Hello community! I' wondering if somebody can explain this to me.
>>
>> Please take look at the snippet.
>>
>>
>> protocol P {}
>>
>> struct X:P {}
>>
>>
>> func foo(_ x:A) {}
>>
>>
>> func bar() {
>>
>>//let x = X() // this compiles
>>
>>let x = X() as P // this does not compile. Why?
>>
>>foo(x)
>>
>> }
>>
>>
>> I expect the both cases to work though. But only first works? And I do
>> not understand why.
>>
>> My coworkers said that it is a compiler bug, but I'm not shure it is.
>>
>> Thanks for the help.
>>
>> ___
>>
>> swift-users mailing list
>>
>> swift-users@swift.org
>>
>> https://lists.swift.org/mailman/listinfo/swift-users
>>
>>
>> ___
>> swift-users mailing list
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>> https://lists.swift.org/mailman/listinfo/swift-users
>>
>> ___
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>> https://lists.swift.org/mailman/listinfo/swift-users
>>
>>
>>
>
>
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Re: [swift-users] Weird protocol behaviour.

2016-12-22 Thread Guillaume Lessard via swift-users
The function foo(x: A){} requires a type which conforms to protocol P.

An existential of protocol P does not actually conform to protocol P.
It’s always been a limitation in Swift: https://bugs.swift.org/browse/SR-55

If the function’s signature were foo(x: P){}, it would work.


Howard’s example swaps the protocol P for a concrete type (P1), which is what 
makes it work.

Cheers,
Guillaume Lessard

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Re: [swift-users] Weird protocol behaviour.

2016-12-22 Thread Howard Lovatt via swift-users
The following variation works:

protocol P {}


class P1:P {}


class X:P1 {}


func foo(_ x:A) {}


func bar() {

//let x = X() // this compiles

let x = X() as P1 // this does not compile. Why?

foo(x)

}

Which adds credence to the bug theory.

Note two changes: 1. two levels of inheritance and 2. change to classes. If
you do two levels using protocols it doesn't work if you use either classes
or structs.


  -- Howard.

On 23 December 2016 at 07:29, Kevin Nattinger  wrote:

> I recall seeing a request on the -evolution list for something like `T :=
> X` to indicate it could be X itself or anything inheriting / implementing
> it, so it’s certainly known behavior, if not desired. IMO it’s a bug and
> `:` should be fixed to include the root type, whether or not that requires
> a discussion on -evolution.
>
> On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users <
> swift-users@swift.org> wrote:
>
> I suspect a compiler bug since A is a P. The equivalent in Java works:
>
> interface P {}
> class X implements P {}
>
>
>  void foo(A x) {}
>
>
> void bar() {
> final P x = new X();
> foo(x);
> }
>
> -- Howard.
>
> On 23 Dec 2016, at 3:19 am, Rien via swift-users 
> wrote:
>
> IMO the error message says it all:
>
> Playground execution failed: error: MyPlayground8.playground:9:5: error:
> cannot invoke 'foo' with an argument list of type '(P)'
>foo(x)
>^
>
> MyPlayground8.playground:9:5: note: expected an argument list of type '(A)'
>foo(x)
>^
>
> I.e. you are passing in a protocol while the function is specified for a
> type.
> Said other way: On which data do you expect the protocol to operate?
>
> Regards,
> Rien
>
> Site: http://balancingrock.nl
> Blog: http://swiftrien.blogspot.com
> Github: http://github.com/Swiftrien
> Project: http://swiftfire.nl
>
>
>
>
> On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users <
> swift-users@swift.org> wrote:
>
>
> Hello community! I' wondering if somebody can explain this to me.
>
> Please take look at the snippet.
>
>
> protocol P {}
>
> struct X:P {}
>
>
> func foo(_ x:A) {}
>
>
> func bar() {
>
>//let x = X() // this compiles
>
>let x = X() as P // this does not compile. Why?
>
>foo(x)
>
> }
>
>
> I expect the both cases to work though. But only first works? And I do not
> understand why.
>
> My coworkers said that it is a compiler bug, but I'm not shure it is.
>
> Thanks for the help.
>
> ___
>
> swift-users mailing list
>
> swift-users@swift.org
>
> https://lists.swift.org/mailman/listinfo/swift-users
>
>
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Re: [swift-users] Weird protocol behaviour.

2016-12-22 Thread Kevin Nattinger via swift-users
I recall seeing a request on the -evolution list for something like `T := X` to 
indicate it could be X itself or anything inheriting / implementing it, so it’s 
certainly known behavior, if not desired. IMO it’s a bug and `:` should be 
fixed to include the root type, whether or not that requires a discussion on 
-evolution.

> On Dec 22, 2016, at 2:17 PM, Howard Lovatt via swift-users 
>  wrote:
> 
> I suspect a compiler bug since A is a P. The equivalent in Java works:
> 
> interface P {}
> class X implements P {}
>  
>  void foo(A x) {}
>  
> void bar() {
> final P x = new X();
> foo(x);
> }
> 
> -- Howard. 
> 
> On 23 Dec 2016, at 3:19 am, Rien via swift-users  > wrote:
> 
>> IMO the error message says it all:
>> 
>> Playground execution failed: error: MyPlayground8.playground:9:5: error: 
>> cannot invoke 'foo' with an argument list of type '(P)'
>>foo(x)
>>^
>> 
>> MyPlayground8.playground:9:5: note: expected an argument list of type '(A)'
>>foo(x)
>>^
>> 
>> I.e. you are passing in a protocol while the function is specified for a 
>> type.
>> Said other way: On which data do you expect the protocol to operate?
>> 
>> Regards,
>> Rien
>> 
>> Site: http://balancingrock.nl 
>> Blog: http://swiftrien.blogspot.com 
>> Github: http://github.com/Swiftrien 
>> Project: http://swiftfire.nl 
>> 
>> 
>> 
>> 
>>> On 22 Dec 2016, at 17:05, Mikhail Seriukov via swift-users 
>>> > wrote:
>>> 
>>> Hello community! I' wondering if somebody can explain this to me.
>>> Please take look at the snippet.
>>> 
>>> protocol P {}
>>> struct X:P {}
>>> 
>>> func foo(_ x:A) {}
>>> 
>>> func bar() {
>>>//let x = X() // this compiles
>>>let x = X() as P // this does not compile. Why?
>>>foo(x)
>>> }
>>> 
>>> I expect the both cases to work though. But only first works? And I do not 
>>> understand why.
>>> My coworkers said that it is a compiler bug, but I'm not shure it is.
>>> Thanks for the help.
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