[swift-evolution] Synthesizing Equatable, Hashable, and Comparable for tuple types

[Douglas Gregor]

> On Nov 21, 2017, at 10:37 PM, Chris Lattner <clattner at nondot.org> wrote:
> 
> On Nov 21, 2017, at 9:25 PM, Douglas Gregor <dgregor at apple.com <mailto:dgregor at apple.com>> wrote:
>>> Or alternatively, one could decide to make the generics system *only and forever* work on nominal types, and make the syntactic sugar just be sugar for named types like Swift.Tuple, Function, and Optional.  Either design could work.
>> 
>> We don’t have a way to make it work for function types, though, because of parameter-passing conventions. Well, assuming we don’t invent something that allows:
>> 
>> 	Function<Double, inout String>
>> 
>> to exist in the type system. Tuple labels have a similar problem.
> 
> I’m totally aware of that and mentioned it upthread.

Eh, sorry I missed it.

>  There are various encoding tricks that could make this work depending on how you want to stretch the current generics system…

I think it’s straightforward and less ugly to make structural types allow extensions and protocol conformances.

	- Doug


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