> On Oct 9, 2016, at 3:43 PM, Charles Srstka via swift-evolution 
> <swift-evolution@swift.org> wrote:
> Let extensions introduce stored properties, but only in the same module as 
> the type’s definition. Then, the compiler can just take any extensions into 
> consideration when it’s determining the size of the type, just as if the 
> properties had been declared in the type. Declaring stored properties on an 
> extension outside of the type’s module results in a compiler error, exactly 
> as today. This would, without any performance drawbacks, solve one of the big 
> problems that people are hoping to solve via stored properties in 
> extensions—the ability to organize members by protocol conformance.

Yes please! A big strong +1 to this from me. I can think of several specific 
chunks of problem code that this would clean up immensely.

Contra Karl in another message, it’s _in-module_ stored property extensions 
that I want most frequently. By far.

It seems to me that Charles’s idea could be introduced as its own proposal. If 
out-of-module stored property extensions do eventually become feasible, then 
Charles’s proposal is a good stepping stone. If they never do, then his 
proposal has done no harm.

I realize this probably falls into the post-ABI stability bucket, but I’d love 
to help write/support the proposal when its time comes.



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