Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Nathan Gray via swift-evolution]

On the other side, I'd say requiring explicit initialization to nil
increases the amount of busywork for the programmer for no good reason.  I
use it all the time and I would be pretty annoyed if it went away.  I would
be pretty shocked if most Swift users don't know that exists.

On Mon, Nov 6, 2017 at 2:33 PM, Slava Pestov via swift-evolution <
swift-evolution@swift.org> wrote:

> Hi all,
>
> Right now, the following two declarations are equivalent:
>
> struct S {
>   var x: Int?
> }
>
> struct S {
>   var x: Int? = nil
> }
>
> That is, mutable bindings of sugared optional type (but not Optional!)
> always have a default value of ‘nil’. This feature increases the surface
> area of the language for no good reason, and I would like to deprecate it
> in -swift-version 5 with a short proposal. Does anyone feel strongly about
> giving it up? I suspect most Swift users don’t even know it exists.
>
> Slava
> ___
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>



-- 
Functional Programmer, iOS Developer, Surfs Poorly
http://twitter.com/n8gray
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Mike Kluev via swift-evolution]

on Mon, 06 Nov 2017 14:33:44 -0800 Slava Pestov  wrote:

Hi all,
>
> Right now, the following two declarations are equivalent:
>
> struct S {
>   var x: Int?
> }
>
> struct S {
>   var x: Int? = nil
> }
>
> That is, mutable bindings of sugared optional type (but not Optional!)
> always have a default value of ‘nil’. This feature increases the surface
> area of the language for no good reason, and I would like to deprecate it
> in -swift-version 5 with a short proposal. Does anyone feel strongly about
> giving it up? I suspect most Swift users don’t even know it exists.
>

value types only or classes as well?

i use the first form (and rely on it every here and there) and to me having
to set to nil explicitly will amount to more visual noise in the source.

btw, what is "the surface area of the language"?

Mike
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Sebestyén Gábor via swift-evolution]

Although I’m fine with the current behavior I’d go for the explicit init form.
Swift promotes explicit value bindings avoiding surprises which I learnt to 
like.

In Java private Optional var; field declaration without RHS simply gets 
inited with a null value and not the expected “none”. Really annoying.

Gábor




Sent from my iPhone

> On 2017. Nov 8., at 9:06, Slava Pestov via swift-evolution 
>  wrote:
> 
> 
> 
>> On Nov 7, 2017, at 11:22 PM, Howard Lovatt via swift-evolution 
>>  wrote:
>> 
>> Not a big deal either way, but I prefer the 2nd (nil) form and therefore 
>> would like to see the 1st form go. It would make Swift more consistent, 
>> consider:
>> 
>> let o: Int? // Looks like nil is assigned.
>> if someTest {
>> o = 1 // Why isn't this an error? (OK I know why - but it looks odd.)
>> } else {
>> o = nil
>> }
>> 
>> 
>> Whilst the above works it is weird because if you are aware that o: Int? 
>> normally assigns nil then the above looks like o, which is a let, is 
>> assigned to twice. If you do the equivalent of the above for a non-optional 
>> it is an error.
> 
> The default initialization behavior is specifically not enabled for let 
> bindings. Compare:
> 
> let x: Int?
> print(x as Any) // error: constant 'x' used before being initialized
> 
> var y: Int?
> print(y as Any)
> 
> So your example is perfectly consistent, because you’re only initializing ‘o’ 
> once (along each control flow path).
> 
> Slava
> 
>> 
>>   -- Howard.
>> 
>>> On 8 November 2017 at 07:54, Adrian Zubarev via swift-evolution 
>>>  wrote:
>>> Same here, but I wouldn’t care much if it were gone.
>>> 
>>> 
>>> Am 7. November 2017 um 21:40:56, David Hart via swift-evolution 
>>> (swift-evolution@swift.org) schrieb:
>>> 
 Yeah, I use the first form constantly.
 
 > On 6 Nov 2017, at 23:33, Slava Pestov via swift-evolution 
 >  wrote:
 > 
 > Hi all,
 > 
 > Right now, the following two declarations are equivalent:
 > 
 > struct S {
 > var x: Int?
 > }
 > 
 > struct S {
 > var x: Int? = nil
 > }
 > 
 > That is, mutable bindings of sugared optional type (but not 
 > Optional!) always have a default value of ‘nil’. This feature 
 > increases the surface area of the language for no good reason, and I 
 > would like to deprecate it in -swift-version 5 with a short proposal. 
 > Does anyone feel strongly about giving it up? I suspect most Swift users 
 > don’t even know it exists.
 > 
 > Slava
 > ___
 > swift-evolution mailing list
 > swift-evolution@swift.org
 > https://lists.swift.org/mailman/listinfo/swift-evolution
 
 ___
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Slava Pestov via swift-evolution]

> On Nov 7, 2017, at 11:22 PM, Howard Lovatt via swift-evolution 
>  wrote:
> 
> Not a big deal either way, but I prefer the 2nd (nil) form and therefore 
> would like to see the 1st form go. It would make Swift more consistent, 
> consider:
> 
> let o: Int? // Looks like nil is assigned.
> if someTest {
> o = 1 // Why isn't this an error? (OK I know why - but it looks odd.)
> } else {
> o = nil
> }
> 
> 
> Whilst the above works it is weird because if you are aware that o: Int? 
> normally assigns nil then the above looks like o, which is a let, is assigned 
> to twice. If you do the equivalent of the above for a non-optional it is an 
> error.

The default initialization behavior is specifically not enabled for let 
bindings. Compare:

let x: Int?
print(x as Any) // error: constant 'x' used before being initialized

var y: Int?
print(y as Any)

So your example is perfectly consistent, because you’re only initializing ‘o’ 
once (along each control flow path).

Slava

> 
>   -- Howard.
> 
> On 8 November 2017 at 07:54, Adrian Zubarev via swift-evolution 
> > wrote:
> Same here, but I wouldn’t care much if it were gone.
> 
> 
> Am 7. November 2017 um 21:40:56, David Hart via swift-evolution 
> (swift-evolution@swift.org ) schrieb:
> 
>> Yeah, I use the first form constantly.
>> 
>> > On 6 Nov 2017, at 23:33, Slava Pestov via swift-evolution 
>> > > wrote:
>> > 
>> > Hi all,
>> > 
>> > Right now, the following two declarations are equivalent:
>> > 
>> > struct S {
>> > var x: Int?
>> > }
>> > 
>> > struct S {
>> > var x: Int? = nil
>> > }
>> > 
>> > That is, mutable bindings of sugared optional type (but not Optional!) 
>> > always have a default value of ‘nil’. This feature increases the surface 
>> > area of the language for no good reason, and I would like to deprecate it 
>> > in -swift-version 5 with a short proposal. Does anyone feel strongly about 
>> > giving it up? I suspect most Swift users don’t even know it exists.
>> > 
>> > Slava
>> > ___
>> > swift-evolution mailing list
>> > swift-evolution@swift.org 
>> > https://lists.swift.org/mailman/listinfo/swift-evolution 
>> > 
>> 
>> ___
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>> https://lists.swift.org/mailman/listinfo/swift-evolution 
>> 
> 
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> 
> 
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Howard Lovatt via swift-evolution]

Not a big deal either way, but I prefer the 2nd (nil) form and therefore
would like to see the 1st form go. It would make Swift more consistent,
consider:

let o: Int? // Looks like nil is assigned.
if someTest {
o = 1 // Why isn't this an error? (OK I know why - but it looks odd.)
} else {
o = nil
}


Whilst the above works it is weird because if you are aware that o: Int?
normally assigns nil then the above looks like o, which is a let, is
assigned to twice. If you do the equivalent of the above for a non-optional
it is an error.

  -- Howard.

On 8 November 2017 at 07:54, Adrian Zubarev via swift-evolution <
swift-evolution@swift.org> wrote:

> Same here, but I wouldn’t care much if it were gone.
>
>
> Am 7. November 2017 um 21:40:56, David Hart via swift-evolution (
> swift-evolution@swift.org) schrieb:
>
> Yeah, I use the first form constantly.
>
> > On 6 Nov 2017, at 23:33, Slava Pestov via swift-evolution <
> swift-evolution@swift.org> wrote:
> >
> > Hi all,
> >
> > Right now, the following two declarations are equivalent:
> >
> > struct S {
> > var x: Int?
> > }
> >
> > struct S {
> > var x: Int? = nil
> > }
> >
> > That is, mutable bindings of sugared optional type (but not
> Optional!) always have a default value of ‘nil’. This feature increases
> the surface area of the language for no good reason, and I would like to
> deprecate it in -swift-version 5 with a short proposal. Does anyone feel
> strongly about giving it up? I suspect most Swift users don’t even know it
> exists.
> >
> > Slava
> > ___
> > swift-evolution mailing list
> > swift-evolution@swift.org
> > https://lists.swift.org/mailman/listinfo/swift-evolution
>
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>
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Adrian Zubarev via swift-evolution]

Same here, but I wouldn’t care much if it were gone.


Am 7. November 2017 um 21:40:56, David Hart via swift-evolution 
(swift-evolution@swift.org) schrieb:

Yeah, I use the first form constantly.

> On 6 Nov 2017, at 23:33, Slava Pestov via swift-evolution 
>  wrote:
>  
> Hi all,
>  
> Right now, the following two declarations are equivalent:
>  
> struct S {
> var x: Int?
> }
>  
> struct S {
> var x: Int? = nil
> }
>  
> That is, mutable bindings of sugared optional type (but not Optional!) 
> always have a default value of ‘nil’. This feature increases the surface area 
> of the language for no good reason, and I would like to deprecate it in 
> -swift-version 5 with a short proposal. Does anyone feel strongly about 
> giving it up? I suspect most Swift users don’t even know it exists.
>  
> Slava
> ___
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> swift-evolution@swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution

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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[David Hart via swift-evolution]

Yeah, I use the first form constantly.

> On 6 Nov 2017, at 23:33, Slava Pestov via swift-evolution 
>  wrote:
> 
> Hi all,
> 
> Right now, the following two declarations are equivalent:
> 
> struct S {
>  var x: Int?
> }
> 
> struct S {
>  var x: Int? = nil
> }
> 
> That is, mutable bindings of sugared optional type (but not Optional!) 
> always have a default value of ‘nil’. This feature increases the surface area 
> of the language for no good reason, and I would like to deprecate it in 
> -swift-version 5 with a short proposal. Does anyone feel strongly about 
> giving it up? I suspect most Swift users don’t even know it exists.
> 
> Slava
> ___
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[T.J. Usiyan via swift-evolution]

I used the existence of the first one in my explanation of explain
optionals. "There is a reasonable default value for an optional type.
'nothing'."

TJ

On Mon, Nov 6, 2017 at 6:52 PM, Slava Pestov via swift-evolution <
swift-evolution@swift.org> wrote:

>
>
> On Nov 6, 2017, at 4:29 PM, Kelvin Ma  wrote:
>
> hot take: i use the second one a lot but only because i always forget the
> first one exists. So I type the = nil just to “be sure”.
>
>
> Yeah, that’s one of my arguments against having the feature, along with
> the simple fact that if the language did not have it already, nobody would
> be requesting this to be added as a special case for optionals.
>
> However, since I also want to avoid needless source compatibility churn,
> I’m fine with keeping the feature — it’s not a huge burden to maintain
> (unlike, say, AnyObject dispatch :) )
>
> Slava
>
>
> On Mon, Nov 6, 2017 at 4:33 PM, Slava Pestov via swift-evolution <
> swift-evolution@swift.org> wrote:
>
>> Hi all,
>>
>> Right now, the following two declarations are equivalent:
>>
>> struct S {
>>   var x: Int?
>> }
>>
>> struct S {
>>   var x: Int? = nil
>> }
>>
>> That is, mutable bindings of sugared optional type (but not Optional!)
>> always have a default value of ‘nil’. This feature increases the surface
>> area of the language for no good reason, and I would like to deprecate it
>> in -swift-version 5 with a short proposal. Does anyone feel strongly about
>> giving it up? I suspect most Swift users don’t even know it exists.
>>
>> Slava
>> ___
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>
>
>
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Slava Pestov via swift-evolution]

> On Nov 6, 2017, at 4:29 PM, Kelvin Ma  wrote:
> 
> hot take: i use the second one a lot but only because i always forget the 
> first one exists. So I type the = nil just to “be sure”.

Yeah, that’s one of my arguments against having the feature, along with the 
simple fact that if the language did not have it already, nobody would be 
requesting this to be added as a special case for optionals.

However, since I also want to avoid needless source compatibility churn, I’m 
fine with keeping the feature — it’s not a huge burden to maintain (unlike, 
say, AnyObject dispatch :) )

Slava

> 
> On Mon, Nov 6, 2017 at 4:33 PM, Slava Pestov via swift-evolution 
> > wrote:
> Hi all,
> 
> Right now, the following two declarations are equivalent:
> 
> struct S {
>   var x: Int?
> }
> 
> struct S {
>   var x: Int? = nil
> }
> 
> That is, mutable bindings of sugared optional type (but not Optional!) 
> always have a default value of ‘nil’. This feature increases the surface area 
> of the language for no good reason, and I would like to deprecate it in 
> -swift-version 5 with a short proposal. Does anyone feel strongly about 
> giving it up? I suspect most Swift users don’t even know it exists.
> 
> Slava
> ___
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> 
> 

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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Jacob Williams via swift-evolution]

> On Nov 6, 2017, at 5:29 PM, Kelvin Ma via swift-evolution 
>  wrote:
> 
> hot take: i use the second one a lot but only because i always forget the 
> first one exists. So I type the = nil just to “be sure”.
> 

Same here! I just changed a bunch of code since I’d forgotten they were the same

> On Mon, Nov 6, 2017 at 4:33 PM, Slava Pestov via swift-evolution 
> > wrote:
> Hi all,
> 
> Right now, the following two declarations are equivalent:
> 
> struct S {
>   var x: Int?
> }
> 
> struct S {
>   var x: Int? = nil
> }
> 
> That is, mutable bindings of sugared optional type (but not Optional!) 
> always have a default value of ‘nil’. This feature increases the surface area 
> of the language for no good reason, and I would like to deprecate it in 
> -swift-version 5 with a short proposal. Does anyone feel strongly about 
> giving it up? I suspect most Swift users don’t even know it exists.
> 
> Slava
> ___
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> 
> 
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Kelvin Ma via swift-evolution]

hot take: i use the second one a lot but only because i always forget the
first one exists. So I type the = nil just to “be sure”.

On Mon, Nov 6, 2017 at 4:33 PM, Slava Pestov via swift-evolution <
swift-evolution@swift.org> wrote:

> Hi all,
>
> Right now, the following two declarations are equivalent:
>
> struct S {
>   var x: Int?
> }
>
> struct S {
>   var x: Int? = nil
> }
>
> That is, mutable bindings of sugared optional type (but not Optional!)
> always have a default value of ‘nil’. This feature increases the surface
> area of the language for no good reason, and I would like to deprecate it
> in -swift-version 5 with a short proposal. Does anyone feel strongly about
> giving it up? I suspect most Swift users don’t even know it exists.
>
> Slava
> ___
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Slava Pestov via swift-evolution]

It sounds like several people rely on this behavior and are actually aware that 
it exists, so I won’t pursue the issue further.

Thanks for the feedback!

> On Nov 6, 2017, at 3:07 PM, Alejandro Martinez  wrote:
> 
> I won’t complain a lot if it’s decided to be removed but I would prefer it to 
> stay. I use it constantly.
> 
> Sent from my iPad
> 
>> On 6 Nov 2017, at 22:41, Jon Shier via swift-evolution 
>>  wrote:
>> 
>>   I use this on all of my mutable optional properties, when I have to use 
>> them. It’s just that little extra bit of code I don’t need to write, and it 
>> feels a lot like parameter defaults in use. By surface area, I assume you 
>> mean the fact that it’s an implicit behavior people may need to remember? As 
>> something like that, this seems like a very small one. As for users knowing 
>> about it, I’m guessing it falls into one of those things that people just 
>> never explicitly notice but would likely have a huge impact on anyone with 
>> lots of mutable optionals. Developers from other languages may also assume 
>> this behavior, since it replicates the “nil by default” behavior seen in 
>> other languages. 
>>   Ultimately, while I won’t feel this deeply, since I tend to view mutable 
>> optionals as poor practice in Swift, it’s a nice little convenience that 
>> will likely impact everyone using mutable optionals. If you really want to 
>> find out, perhaps run it agains the compatibility suite?
>> 
>> 
>> Jon
>> 
>>> On Nov 6, 2017, at 5:33 PM, Slava Pestov via swift-evolution 
>>>  wrote:
>>> 
>>> Hi all,
>>> 
>>> Right now, the following two declarations are equivalent:
>>> 
>>> struct S {
>>> var x: Int?
>>> }
>>> 
>>> struct S {
>>> var x: Int? = nil
>>> }
>>> 
>>> That is, mutable bindings of sugared optional type (but not Optional!) 
>>> always have a default value of ‘nil’. This feature increases the surface 
>>> area of the language for no good reason, and I would like to deprecate it 
>>> in -swift-version 5 with a short proposal. Does anyone feel strongly about 
>>> giving it up? I suspect most Swift users don’t even know it exists.
>>> 
>>> Slava
>>> ___
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Alejandro Martinez via swift-evolution]

I won’t complain a lot if it’s decided to be removed but I would prefer it to 
stay. I use it constantly.

Sent from my iPad

> On 6 Nov 2017, at 22:41, Jon Shier via swift-evolution 
>  wrote:
> 
>I use this on all of my mutable optional properties, when I have to use 
> them. It’s just that little extra bit of code I don’t need to write, and it 
> feels a lot like parameter defaults in use. By surface area, I assume you 
> mean the fact that it’s an implicit behavior people may need to remember? As 
> something like that, this seems like a very small one. As for users knowing 
> about it, I’m guessing it falls into one of those things that people just 
> never explicitly notice but would likely have a huge impact on anyone with 
> lots of mutable optionals. Developers from other languages may also assume 
> this behavior, since it replicates the “nil by default” behavior seen in 
> other languages. 
>Ultimately, while I won’t feel this deeply, since I tend to view mutable 
> optionals as poor practice in Swift, it’s a nice little convenience that will 
> likely impact everyone using mutable optionals. If you really want to find 
> out, perhaps run it agains the compatibility suite?
> 
> 
> Jon
> 
>> On Nov 6, 2017, at 5:33 PM, Slava Pestov via swift-evolution 
>>  wrote:
>> 
>> Hi all,
>> 
>> Right now, the following two declarations are equivalent:
>> 
>> struct S {
>> var x: Int?
>> }
>> 
>> struct S {
>> var x: Int? = nil
>> }
>> 
>> That is, mutable bindings of sugared optional type (but not Optional!) 
>> always have a default value of ‘nil’. This feature increases the surface 
>> area of the language for no good reason, and I would like to deprecate it in 
>> -swift-version 5 with a short proposal. Does anyone feel strongly about 
>> giving it up? I suspect most Swift users don’t even know it exists.
>> 
>> Slava
>> ___
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Jon Shier via swift-evolution]

I use this on all of my mutable optional properties, when I have to use 
them. It’s just that little extra bit of code I don’t need to write, and it 
feels a lot like parameter defaults in use. By surface area, I assume you mean 
the fact that it’s an implicit behavior people may need to remember? As 
something like that, this seems like a very small one. As for users knowing 
about it, I’m guessing it falls into one of those things that people just never 
explicitly notice but would likely have a huge impact on anyone with lots of 
mutable optionals. Developers from other languages may also assume this 
behavior, since it replicates the “nil by default” behavior seen in other 
languages. 
Ultimately, while I won’t feel this deeply, since I tend to view 
mutable optionals as poor practice in Swift, it’s a nice little convenience 
that will likely impact everyone using mutable optionals. If you really want to 
find out, perhaps run it agains the compatibility suite?


Jon

> On Nov 6, 2017, at 5:33 PM, Slava Pestov via swift-evolution 
>  wrote:
> 
> Hi all,
> 
> Right now, the following two declarations are equivalent:
> 
> struct S {
>  var x: Int?
> }
> 
> struct S {
>  var x: Int? = nil
> }
> 
> That is, mutable bindings of sugared optional type (but not Optional!) 
> always have a default value of ‘nil’. This feature increases the surface area 
> of the language for no good reason, and I would like to deprecate it in 
> -swift-version 5 with a short proposal. Does anyone feel strongly about 
> giving it up? I suspect most Swift users don’t even know it exists.
> 
> Slava
> ___
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Matthew Johnson via swift-evolution]

> On Nov 6, 2017, at 4:33 PM, Slava Pestov via swift-evolution 
>  wrote:
> 
> Hi all,
> 
> Right now, the following two declarations are equivalent:
> 
> struct S {
>  var x: Int?
> }
> 
> struct S {
>  var x: Int? = nil
> }
> 
> That is, mutable bindings of sugared optional type (but not Optional!) 
> always have a default value of ‘nil’. This feature increases the surface area 
> of the language for no good reason, and I would like to deprecate it in 
> -swift-version 5 with a short proposal. Does anyone feel strongly about 
> giving it up? I suspect most Swift users don’t even know it exists.

I don’t have too strong an opinion on this, leaning towards being supportive.  
That said, I think you underestimate the source breakage it will cause.  I have 
seen a lot  of code this change will break (albeit in a trivial way that’s easy 
to migrate).

> 
> Slava
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Re: [swift-evolution] Pitch: Remove default initialization of optional bindings

[Adrian Zubarev via swift-evolution]

Just a quick question for clarification. What will happen to these? Do we have 
to provide the default value ourselves?

class ViewController : UIViewController {

    @IBOutlet weak var view1: UIView?

    @IBOutlet weak var view2: UIView!
}


Am 6. November 2017 um 23:33:51, Slava Pestov via swift-evolution 
(swift-evolution@swift.org) schrieb:

Hi all,

Right now, the following two declarations are equivalent:

struct S {
var x: Int?
}

struct S {
var x: Int? = nil
}

That is, mutable bindings of sugared optional type (but not Optional!) 
always have a default value of ‘nil’. This feature increases the surface area 
of the language for no good reason, and I would like to deprecate it in 
-swift-version 5 with a short proposal. Does anyone feel strongly about giving 
it up? I suspect most Swift users don’t even know it exists.

Slava
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[swift-evolution] Pitch: Remove default initialization of optional bindings

[Slava Pestov via swift-evolution]

Hi all,

Right now, the following two declarations are equivalent:

struct S {
  var x: Int?
}

struct S {
  var x: Int? = nil
}

That is, mutable bindings of sugared optional type (but not Optional!) 
always have a default value of ‘nil’. This feature increases the surface area 
of the language for no good reason, and I would like to deprecate it in 
-swift-version 5 with a short proposal. Does anyone feel strongly about giving 
it up? I suspect most Swift users don’t even know it exists.

Slava
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