[swift-evolution] [Pitch] separate syntax of class inheritance and protocol conformance

[Charlie Monroe]

Coming to someone elses code, it adds an extra effort to understand the declaration. Putting inheritance and conformance separately makes the declaration easier to read. At least for me.

> On Jul 22, 2016, at 4:05 PM, Brandon Knope <bknope at me.com> wrote:
> 
> Honest question: what is actually confusing about the current behavior?
> 
> I.E. What is important about knowing whether "DataSource" is a class or a protocol?
> 
> I thought the blurred distinction was intentional?
> 
> Brandon 
> 
>> On Jul 22, 2016, at 9:47 AM, Charlie Monroe via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> I agree that this is an issue. Mostly nowadays when more and more classes in Swift do not have a superclass - it simply looks weird:
>> 
>> class MyClass: DataSource
>> 
>> One doesn't know whether "DataSource" is a class, protocol, etc. Nevertheless, I do not feel that :: is the answer. I really liked, how ObjC did it (which isn't possible with the generics now - is it?), but what about something like this?
>> 
>> class BaseClass [SomeDelegate, OtherDelegate, ProtocolX]
>> class MyClass: BaseClass [SomeDelegate, OtherDelegate, ProtocolX]
>> extension MyClass [OtherProtocol]
>> 
>> 
>>> On Jul 22, 2016, at 3:14 PM, Vladimir.S via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> I remember that this was discussed, but can't find any decision regarding this.. So, as a last chance, don't we want in Swift 3.0, as big source breaking change, separate class inheritance and protocol conformance in syntax?
>>> 
>>> Sorry if there was a decision about this suggestions. Please let know in this case.
>>> 
>>> I.e. when I see the following I can't understand if the class inherits from base class and conforms to protocols or just conforms to two protocols:
>>> 
>>> class MyClass : First, Second, Third {
>>> }
>>> 
>>> We don't have a rule to name protocols with 'Protocol'/other suffix/prefix, or classes with 'T'/'C' prefix or something like this, so I believe to improve the clarity of code we should separate in syntax inheritance and conformance.
>>> 
>>> As I understand we should discuss changes in these areas:
>>> 
>>> 1. class inheritance :
>>> class Child: BaseClass
>>> 
>>> 2. class conformance :
>>> class Child: SomeProtocol1, SomeProtocol2
>>> 
>>> 3. class inheritance + conformance :
>>> class Child: BaseClass, SomeProtocol1, SomeProtocol2
>>> 
>>> 4. protocol conformance for structs:
>>> struct Struct: SomeProtocol1, SomeProtocol2
>>> 
>>> 5. protocol inheritance:
>>> protocol Child: BaseProtocol1, BaseProtocol2
>>> 
>>> 
>>> My suggestions:
>>> 
>>> I) separate inheritance with double colon :
>>> 
>>> 1. class inheritance :
>>> class Child:: BaseClass
>>> 
>>> 2. class conformance :
>>> class Child: SomeProtocol1, SomeProtocol2
>>> 
>>> 3. class inheritance + conformance :
>>> class Child:: BaseClass : SomeProtocol1, SomeProtocol2
>>> 
>>> 4. protocol conformance for structs:
>>> struct Struct: SomeProtocol1, SomeProtocol2
>>> 
>>> 5. protocol inheritance:
>>> protocol Child:: BaseProtocol1, BaseProtocol2
>>> 
>>> 
>>> II) in class definition use parenthesis to separate inheritance and conformance :
>>> 
>>> 1. class inheritance :
>>> class Child: BaseClass
>>> 
>>> 2. class conformance :
>>> class Child: (SomeProtocol1, SomeProtocol2)
>>> 
>>> 3. class inheritance + conformance :
>>> class Child: BaseClass (SomeProtocol1, SomeProtocol2)
>>> 
>>> 4. protocol conformance for structs:
>>> struct Struct: SomeProtocol1, SomeProtocol2
>>> or
>>> struct Struct: (SomeProtocol1, SomeProtocol2)
>>> should be discussed
>>> 
>>> 5. protocol inheritance:
>>> protocol Child: BaseProtocol1, BaseProtocol2
>>> 
>>> 
>>> III) special word like 'conforms'
>>> 
>>> 1. class inheritance :
>>> class Child: BaseClass
>>> 
>>> 2. class conformance :
>>> class Child: conforms SomeProtocol1, SomeProtocol2
>>> or
>>> class Child conforms SomeProtocol1, SomeProtocol2
>>> 
>>> 3. class inheritance + conformance :
>>> class Child: BaseClass conforms SomeProtocol1, SomeProtocol2
>>> 
>>> 4. protocol conformance for structs:
>>> struct Struct: conforms SomeProtocol1, SomeProtocol2
>>> or
>>> struct Struct conforms SomeProtocol1, SomeProtocol2
>>> 
>>> 5. protocol inheritance:
>>> protocol Child: BaseProtocol1, BaseProtocol2
>>> 
>>> 
>>> Thoughts?
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>> 
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