[swift-evolution] [Discussion] Using dot prefixes to infer non-enumeration static members

[Erica Sadun]

Sounds like a compelling response to me. Thanks, Jordan.

-- E

> On Feb 15, 2016, at 11:40 AM, Jordan Rose <jordan_rose at apple.com> wrote:
> 
>> 
>> On Feb 15, 2016, at 8:58, Erica Sadun via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> While discussing leading enumeration dot prefixes, Howard Lovatt asked why static properties and methods could not be inferred via a dot prefix as well. Based on Swift-Evolution conventions, here's a new thread to discuss this idea: specifically, would it be beneficial (and/or possible) to use dot prefixes to denote static member references in instance member code.
>> 
>> Howard wrote:
>> 
>>> +1 for the proposal, it is wierd to use `.` in some places and not others. 
>>> 
>>> On the subject of static methods and properties in general, would it be possible for `.name` to be a reference to a static and `name` a reference to an instance? EG:
>>> 
>>>     .name = x // static
>>>     name = x // instance
>>>     x = name + .name // instance + static
>>>     r = name ... .name // instance ... static, needs space
>>>     r = name...Type.name // Can still qualify with type name
>>> 
>> 
>> Under the current system, you must explicitly name or derive a type to access static members from instance member implementations.
>> 
>> struct MyStruct {
>>     static func staticMember() {}
>>     
>>     func instanceMember() {
>>         // name a type
>>         MyStruct.staticMember() // works
>> 
>>         // derive a type
>>         self.dynamicType.staticMember() // works
>>         
>>         // error: value of tuple type '()' has no member 'staticMember'
>>         // does not work
>>         .staticMember()
>>     }
>> }
>> 
>> Using dot prefixes for static member access:
>> 
>> * Has precedent in enumeration members
>> * Would streamline Swift code
>> * Is visually differentiated from `self`-prefixed instance member references
>> 
>> What are your thoughts, both technical and philosophical, on a change like this? Thanks in advance for your feedback.
> 
> Dot-prefixed member expressions are currently looked up as static members of the contextual type, which lets you do things like this:
> 
> import AppKit
> let colors: [NSColor] = [.redColor(), .blueColor()]
> 
> I don't think we want to change or overload that rule to also look up static members of the enclosing lexical context type (i.e. the type of 'self').
> 
> Jordan

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