[swift-evolution] Proposal: Re-instate mandatory self for accessing instance properties and functions

[ilya]

> It might seem obvious in a small piece of code like yours, but it becomes
less so in a class several hundred of lines long.

I'll be happy to take a look at the specific examples and see if perhaps
self-dot access will be useful there.
But even if we disagree you're still able to use self-dot access in any
place where you feel this to be beneficial without any changes in the
language.

> Why use a style guide when the language can enforce rules to eliminate
the ambiguity?

Because each project's situation can be unique. For the same reason there's
no need to rush to add concurrency at the language level without
considering other possibilities first.

For the record I would also like it if the "globals must start with an
uppercase letter" rule were enforced by the compiler (well, not in the
playground, those aren't true globals).

It still looks to me that if we make compiler enforce that and the
"instance names must not start with an uppercase letter" rule this
eliminates the ambiguity discussed in this thread.

On Sun, Dec 13, 2015 at 13:12 David Hart <david at hartbit.com
<javascript:_e(%7B%7D,'cvml','david at hartbit.com');>> wrote:

> struct Vector {
>     var dx: Double
>     var dy: Double
>     var length: Double { return sqrt(dx*dx + dy*dy) }
> }
>
> vs
>
> struct Vector {
>     var dx: Double
>     var dy: Double
>     var length: Double { return sqrt(@dx*@dx + @dy*@dy) }
> }
>
> struct Vector {
>     var dx: Double
>     var dy: Double
>     var length: Double { return sqrt(self.dx*self.dx + self.dy*self.dy) }
> }
>
>
> I don't agree with you because when reading your first example, I have to
> make a mental gymnastic to find out if the variables are local/global
> variables or if they are instance properties. It might seem obvious in a
> small piece of code like yours, but it becomes less so in a class several
> hundred of lines long.
>
> On 13 Dec 2015, at 10:48, ilya <ilya.nikokoshev at gmail.com
> <javascript:_e(%7B%7D,'cvml','ilya.nikokoshev at gmail.com');>> wrote:
>
> > For me, readability has always been more important, as we spend most of
> our time reading than writing code.
> Agree.
>
> > but they make code editing easier at the expense of readability.
> Disagree. This really depends on the example. E.g. which is more readable:
>
> struct Vector {
>     var dx: Double
>     var dy: Double
>     var length: Double { return sqrt(dx*dx + dy*dy) }
> }
>
> vs
>
> struct Vector {
>     var dx: Double
>     var dy: Double
>     var length: Double { return sqrt(@dx*@dx + @dy*@dy) }
> }
>
> struct Vector {
>     var dx: Double
>     var dy: Double
>     var length: Double { return sqrt(self.dx*self.dx + self.dy*self.dy) }
> }
>
>
>
> On Sun, Dec 13, 2015 at 12:40 PM, David Hart <david at hartbit.com
> <javascript:_e(%7B%7D,'cvml','david at hartbit.com');>> wrote:
>
>> Hi Ilya,
>>
>> Why use a style guide when the language can enforce rules to eliminate
>> the ambiguity?
>>
>> On the other hand, it allows a logical explanation of how you can take
>> code from global scope and put it into an instance scope
>>
>>
>> This helps implementing patterns like "take a long function and make it
>> into a struct with a bunch of small functions instead".
>>
>>
>> Both of your previous points make sense but they make code editing easier
>> at the expense of readability. For me, readability has always been more
>> important, as we spend most of our time reading than writing code.
>>
>> That's why I suggest using .x and .f() to mark implicit self.
>>>
>>
>> I agree that that would potentially add confusion to the grammar. I've
>> always liked the @ and @@ prefixes of Ruby for accessing instance and class
>> properties, but I agree that symbols like that would feel a bit foreign in
>> Swift.
>>
>> David
>>
>> On 13 Dec 2015, at 10:16, ilya via swift-evolution <
>> swift-evolution at swift.org
>> <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> wrote:
>>
>> > But implicit self is confusing in a lot of code
>>
>> On the other hand, it allows a logical explanation of how you can take
>> code from global scope and put it into an instance scope:
>>
>> let greeting = "Hello"
>> let name = "Michael"
>>
>> func greet() {
>>     print("\(greeting), \(name)")
>> }
>>
>> seemlessly becomes
>>
>> class Greeter {
>>
>>     let greeting = "Hello"
>>     let name = "Michael"
>>
>>     func greet() {
>>         print("\(greeting), \(name)")
>>     }
>>
>> }
>>
>> > can (and does) lead to shadowing bugs,
>>
>> There are simple strategies that help to minimize the amount of
>> shadowing, e.g.
>>
>> - only expose the minimum necessary amount of names in any scope
>> - break functions into small part so that it's easy to see all the local
>> name declarations
>> - not use any globals, or at least name them in a visually different way
>> (UppercaseCamelStyle)
>> - name properties and locals in a different way (classProperty, local_var)
>>
>> Even without a formal code style, if you tend to make property names
>> longer and local names shorter, your risk of shadowing goes down.
>>
>> > .x and .f() to mark implicit self. I realize that this may conflict
>> with enum usage.
>>
>> This will lead to a lot of ambiguity:
>>
>> func f() {
>>     let x = NSOperation()
>>     .name = "Name" // is it x.name or self.name??
>>    ...
>> }
>>
>> >  If so, then use another marker. For instance :x or ^x or anything.
>>
>> This is workable, but still I think this is one of the best points of
>> Swift – the existence of instance scope where names are simply written
>> as-is. This helps implementing patterns like "take a long function and make
>> it into a struct with a bunch of small functions instead".
>>
>> > is very difficult to reason about in diffs or any other interface that
>> isn't an IDE (especially code review)
>>
>> This is the point where I entirely agree, good code should be easily read
>> in any context.
>> Again, may I suggest you take a look into using a style guide to
>> differentiate visually between local and instance scope?
>>
>> Ilya
>>
>> On Sun, Dec 13, 2015 at 10:15 AM, Rob Napier via swift-evolution <
>> swift-evolution at swift.org
>> <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> wrote:
>>
>>> I wanted to reopen this discussion that seems to have trailed off.
>>> Requesting the return of self was my very first ask of Swift if I remember
>>> correctly (https://devforums.apple.com/message/1013085). Continued work
>>> in Swift has both strengthened and modified that ask. Here are several of
>>> the examples discussed before:
>>>
>>> https://gist.github.com/schwa/94b11dc0a7a331f46b25
>>> https://gist.github.com/rnapier/478465d1b15e95b98b42
>>> https://gist.github.com/rnapier/4213dc64206b17df6935
>>> https://gist.github.com/dwineman/d6c56ec0c0e2fdb761db
>>>
>>> I get that it seems tedious to type (and read) "self." and I get that
>>> "self." is currently a hint that self might be captured (but doesn't
>>> actually mean that, since you can use self. without capturing, and
>>> sometimes have to, very often in init, so really it's basically meaningless
>>> for that use).
>>>
>>> That's why I suggest using .x and .f() to mark implicit self. I realize
>>> that this may conflict with enum usage. If so, then use another marker. For
>>> instance :x or ^x or anything. But implicit self is confusing in a lot of
>>> code, can (and does) lead to shadowing bugs, and is very difficult to
>>> reason about in diffs or any other interface that isn't an IDE (especially
>>> code review).
>>>
>>> Thoughts, David? I agree with your basic proposal; I just want to amend
>>> it.
>>>
>>> -Rob
>>>
>>>
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>>> swift-evolution at swift.org
>>> <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>
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>>>
>>>
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>
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