[swift-evolution] Proposal SE-0009 Reconsideration

Michael Peternell michael.peternell at gmx.at
Wed May 18 16:01:34 CDT 2016


> Am 18.05.2016 um 21:53 schrieb Goffredo Marocchi via swift-evolution <swift-evolution at swift.org>:
> 
> The code you pasted  really ought to print a warning out (allowing variable shadowing without even a warning can lead to annoying bugs), a generation of Swift developers will be trained by relying on the Swift compiler to make their code automagically safe and this is another one of those Not Fun To Debug bits (similar to the dispatching rules of protocol extensions default methods).

There are dispatching rules of protocol extension default methods? I thought the methods are selected randomly... just kidding - I think this issue would be worth a proposal...

> 
> Sent from my iPhone
> 
>> On 18 May 2016, at 17:39, Vladimir.S via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> Fully support your opinion. +1 for warning option.
>> Also, I believe we need a warning (not error as suggested by @Sean in reply to this thread) when type's property shadowed with local variable.
>> 
>> Or do we *really* feel that this code don't require at least a warning ?? :
>> 
>> class A {
>>   var x = 100
>> 
>>   func f() {
>>       let x = 10
>>       print(x)
>>   }
>> }
>> 
>> 
>>> On 18.05.2016 8:09, Krystof Vasa via swift-evolution wrote:
>>> Hi there,
>>> 
>>> I've been an OS X developer for over a decade now and was a huge fan of ObjC, implementing ObjC runtime into FreeBSD kernel as a intern at Cambridge University and my Masters thesis was a modular ObjC runtime that ran on Win 3.11. With the advance of Swift, it was clear to me, however, that this is a point to say goodbye to ObjC and move to Swift.
>>> 
>>> And so, I've migrated all my projects over 5 months into Swift, which is over 200 KLOC of code, with one project being 90 KLOC. This has lead unfortunately to various hiccups due to bugs in Swift, Xcode, compiler, where I was unable to build a project for a month, etc. - I've filed 84 bug reports at bugreport.apple.com over the past few months regarding developer tools (including Swift) and have begun closely watching the evolution of Swift.
>>> 
>>> While I strongly disagree with the rejection of SE-0009, I understood the reasoning that it's a boilerplate to keep adding self. in front of all variables. I personally always refer to self when accessing instance variables (and methods), unless they are private variables starting with underscore. I know the underscore thing isn't very Swift-y, but on the other hand, reading the code you immediately know you are dealing with a private instance variable, not something local.
>>> 
>>> This was until I spent 2 hours chasing a bug that was caused by the exact issue this proposal was trying to prevent. I was furious.
>>> 
>>> a) When you read someone elses code and you see myVar.doSomething(), you assume it's refering to a local variable. Which is incredibly confusing, if this is an instance variable. Swift is all about compile-time checks and this is where it fails.
>>> 
>>> b) If you indeed decide not to go with this proposal, please consider adding a warning option. When you take a look at LLVM warning options, I bet there would be a place for this. Let the user decide. I personally would immediately turn it on on all my projects. Don't make it an error, make it a warning.
>>> 
>>> I speak to you as someone with quite a huge real-life experience with Swift, mainly in the last year - the question whether to force the reference to self is something that may be dividing the community, but I believe that most people with more developing experience would be all for this. At least as an option.
>>> 
>>> Sincerely yours,
>>> 
>>> Krystof Vasa
>>> 
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