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

[Vladimir.S]

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?