[swift-users] override-like keyword for default implementations

[Vladimir.S]

On 16.05.2017 20:44, Charles Srstka via swift-users wrote:
>> On May 16, 2017, at 12:32 PM, Nevin Brackett-Rozinsky via swift-users 
>> <swift-users at swift.org <mailto:swift-users at swift.org>> wrote:
>>
>> There is not.
>>
>> At some point in the future, I believe the plan is to eventually allow default 
>> implementations to be written in-line within the protocol declaration itself. In 
>> other words, the fact that default implementations currently must appear in 
>> extensions, is a temporary limitation that has not yet been a priority to address.

Very interested, why do you have this impression? I didn't see this idea in the list 
previously(probably I just missed it). I strongly believe there can't be such 'plan'.

>>
>> Once we gain the ability to define default implementations within protocols 
>> themselves, rather than extensions, then your use-case will “just work” (at least 
>> as long as you control the protocol anyway). I wouldn’t hold my breath though, as 
>> that behavior will not appear this year, and the plans for next year have not been 
>> hashed out yet.
> 
> Even that won’t completely solve the problem, though, because:
> 
> protocol P {
> func foo() {
> // default implementation
> }
> }
> 
> struct S: P {
> func foo() {
> // overriden implementation
> }
> }
> 
> If foo is refactored here, S will start getting the wrong implementation of it, 
> silently, with no warning.
> 
> People have tried to bring up proposals to add some sort of “override”-like keyword 
> for protocols on swift-evolution a bunch of times, but it always gets shouted down by 
> certain members of the group, so we’re probably permanently stuck with this situation 
> where a supposedly “protocol-oriented” language is not safe to use with protocols.

Exactly!
I can remember these related threads in swift-evolution:
"Requiring proactive overrides for default protocol implementations"
"Requiring special keyword to mark protocol implementation methods"


> 
> Charles
> 
> 
> 
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