[swift-dev] Disallowing weak struct properties

Austin Zheng austinzheng at gmail.com
Fri Jan 29 20:05:23 CST 2016

+1, and +1 to first-class weak-supporting sets and hash tables.


On Fri, Jan 29, 2016 at 5:56 PM, Jordan Rose via swift-dev <
swift-dev at swift.org> wrote:

> Hi, everyone. What do you think about dropping support for 'weak' in
> struct properties? This would fix a semantic issue—'let' structs containing
> weak properties won't change out from under you—and (AFAICT) would make all
> values trivially movable, which is a great quality to have.
> This wouldn't change local variables, top-level variables, or class
> properties, just structs. It *would* make having an array of weak
> references a little harder, but honestly we should have proper
> weak-supporting collections anyway; as I understand it the behavior you
> usually want is auto-compacting rather than leaving a hole. (Evidence:
> Cocoa has NSHashTable for weak sets and NSMapTable for dictionaries with
> weak keys and/or values; there's no variant of NSArray that supports weak
> references other than by making a custom CFArray and being very very
> careful how you access it.)
> Anyway, thoughts? It's not really my department but it cleans up the same
> areas that are being affected by struct resilience.
> Jordan
> P.S. I know this would have to go through swift-evolution for real. I just
> want to know if it's a silly idea to begin with.
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