[swift-evolution] [Review] SE-0077: Improved operator declarations

[Matthew Johnson]

> On May 20, 2016, at 4:22 PM, Антон Жилин <antonyzhilin at gmail.com> wrote:
> 
> Yes, in this case it should be allowed, because this relationship already existed in imported modules. I will add that, too, thanks!

Cool.

What is the latest syntax you are using?  Did you consider any of the lighter weight options?  That subthread died without conclusion (unless I missed something somehow).


> 
> - Anton
> 
> 2016-05-21 0:01 GMT+03:00 Matthew Johnson <matthew at anandabits.com <mailto:matthew at anandabits.com>>:
> 
>> On May 20, 2016, at 3:51 PM, John McCall <rjmccall at apple.com <mailto:rjmccall at apple.com>> wrote:
>> 
>>> On May 20, 2016, at 1:25 PM, Антон Жилин <antonyzhilin at gmail.com <mailto:antonyzhilin at gmail.com>> wrote:
>>> Inline:
>>> 
>>> 2016-05-20 20:58 GMT+03:00 John McCall <rjmccall at apple.com <mailto:rjmccall at apple.com>>:
>>> The transitivity rule plus the ability to define precedence relationships in both directions on a new precedence group allows a new precedence group to create a precedence relationship between existing unrelated precedence groups.  This should be forbidden.
>>> 
>>> Agreed, although there is an alternate solution to allow global-scope relationship definition.
>>> Trying to write it formally:
>>> 
>>> ====begin====
>>> Precedence relationships that, by transitivity rule, create relationship between two imported groups, is an error. Example:
>>> 
>>> // Module X
>>> precedencegroup A { }
>>> precedencegroup C { }
>>> 
>>> // Module Y
>>> import X
>>> precedencegroup B { precedence(> A) precedence(< C) }
>>> 
>>> This results in compilation error "B uses transitivity to define relationship between imported groups A and C".
>>> The rationale behind this is that otherwise one can create relationships between standard precedence groups that are confusing for the reader.
>>> ====end====
>> 
>> Seems good to me.
> 
> Would this be allowed if Module X already defined precedence group C > A (it would not be defining a *new* relationship between A and C in that case)?
> 
>> 
>>> What's the purpose of equality relationships between precedence groups?
>>> 
>>> Agreed, will remove.
>> 
>> Ok.
>>  
>>> Your proposal should call out the special treatment of the Assignment and Ternary groups.
>>> 
>>> Do you mean that most operators should define greater precedence than Assignment / Ternary? Or there should be some other special treatment?
>> 
>> Just that they have implicit members.
>> 
>> John.
> 
> 

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