[swift-evolution] [Draft] A Consistent Foundation For Access Control: Scope-Bounded Capabilities

[Matthew Johnson]

Sent from my iPad

> On Mar 4, 2017, at 10:09 AM, Rien <Rien at Balancingrock.nl> wrote:
> 
> 
>> On 04 Mar 2017, at 16:01, Matthew Johnson via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> I have updated this proposal with a few more refinements based on yesterday’s discussion.  You can find the final proposal on Github:
>> 
>> https://github.com/anandabits/swift-evolution/blob/scope-bounded-capabilities/proposals/NNNN-scope-bounded-capabilities.md.
>> 
>> Matthew
>> 
>>> On Mar 2, 2017, at 1:58 PM, Matthew Johnson via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> ...
>>> The rules which make up the essential complexity in Swift's access control system are:
>>> 
>>>    • The default scope for all capabilites a declaration offers is module-wide (or submodule-wide in the future).
>>>    • The scope of a capability may be modified by an explicit access modifier.
>>>    • The scope of an additional capability is implicitly bounded by the scope of the basic capability.
>>>    • The scope of an additional capability may not be explicitly specified as greater than that of the basic capability.
>>>    • If no scope is explicitly provided for the basic capability and an additional capability is specified to be available outside the (sub)module the basic capability is also given the same availability.
>>>    • The scope of a declaration (including all capabilities) may be bounded by the declaration of ancestor.
> 
> Do you mean: IS bounded by?

No, not necessarily.  If the declaration is bounded to the module and all ancestors are public the ancestors don't bound really bound it.  I suppose you could say the ancestor still provides a bound that is just never reached.  I'm that sense, it depends on how you want to look at it.  :)

> 
> 
>>>    • The scope of a declaration may not be greater than the scope of the capabilities necessary to use that declaration: if you can't see a parameter type you can't call the function.
>>> Most of these rules already exist in Swift's access control system. There is one change and one addition:
> 
> Overall I think the draft is pretty solid.
> Imo this would give Swift the best available access control system I know of ;-)
> Thanks for your work on this!

I'm glad to hear you like it!  Thanks!  I'm hoping the core team is willing to review it for Swift 4 and feedback continues to be positive.  It feels like something that should be done in Swift 4 if we're going to do it.

> 
> Regards,
> Rien
> 
> Site: http://balancingrock.nl
> Blog: http://swiftrien.blogspot.com
> Github: http://github.com/Balancingrock
> Project: http://swiftfire.nl
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