[swift-evolution] 'T =?utf-8?Q?=21=3D_?=Type' in where clause

[Adrian Zubarev]

The or operator for types is rejected in Swift, and probably won’t ever make it, however there might be hope for enums to solve this issue. Some people pointed out in different threads how enums could mimic such behavior.

+1 for != type operator

I bumped myself once or twice into such a scenario, but I cannot remember what the use case was back then.



-- 
Adrian Zubarev
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Am 28. Februar 2017 um 08:22:07, Nicolas Fezans via swift-evolution (swift-evolution at swift.org) schrieb:

+1
I would also welcome to be able to use "or" and "and" logical operators (not only the not operator) on these constraints.
I have sometimes generic functions whose code is identical but is written twice: first with 'where T=P1' and then with 'where T=P2', being able to write for instance 'where T=(P1 or P2)' would be very handy IMO.
One could often argue that additional protocols and extensions could be defined as a workaround to the situation I just mentioned but it seems often a bit of an overkill to me when you only have a couple of functions with that combination of requirements.


Nicolas

On Tue, Feb 28, 2017 at 7:53 AM, Nicholas Maccharoli via swift-evolution <swift-evolution at swift.org> wrote:
+ 1 
 I personally find this frustrating, but at the same time Im curious as to what the argument against 
introducing this is. 

- Nick 

On Tue, Feb 28, 2017 at 3:21 PM, David Sweeris via swift-evolution <swift-evolution at swift.org> wrote:



Sent from my iPhone
> On Feb 27, 2017, at 16:34, Rex Fenley via swift-evolution <swift-evolution at swift.org> wrote:
>
> I often find myself running into situations where I'll receive "Ambiguous use of..." for overloaded functions or operators. In every case these situations would be easily solved if I could specify "Generic != CertainType" in the where clause of one of the overloads so I can disambiguate the cases. Could this be added to language?

+ all the 1s, along with something like "where !(T: Foo)"

IIRC, the topic has come up before, though I couldn't (quickly) find it and don't recall what the response was (other than some variation of "no", since we don't have it).

- Dave Sweeris


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