[swift-users] Overload Resolution of Binary Operators

[Toni Suter]

@David
If you would split up the statement like this...

let x = 0 *** 4
let result = x +++ 0

... the compiler would report an ambiguity error, because both overloads of *** are valid and of equivalent priority.
You could do something like this though:

let x: Int = 0 *** 4	// picks f2
let result = x +++ 0	// picks f4

or this:

let x: String = 0 *** 4	// picks f1
let result = x +++ 0	// picks f3

Now the compiler has enough type information to know which overload to pick.

@Mark
Ok, thanks. I reported a bug at https://bugs.swift.org/browse/SR-3209 <https://bugs.swift.org/browse/SR-3209> and assigned it to you.

@Rien
Yes, it is even possible to use the operators as the example above shows, but it is requires a bit more explicit
type information so that the type checker knows which overload to pick.

Thanks and best regards,
Toni

> Am 15.11.2016 um 08:41 schrieb Rien <Rien at Balancingrock.nl>:
> 
> I seem to remember that while it is possible to define, the compiler will yield an error if you try to use the functions (“cannot resolve”).
> 
> Regards,
> Rien
> 
> Site: http://balancingrock.nl
> Blog: http://swiftrien.blogspot.com
> Github: http://github.com/Swiftrien
> Project: http://swiftfire.nl
> 
> 
> 
> 
>> On 14 Nov 2016, at 23:05, Toni Suter via swift-users <swift-users at swift.org> wrote:
>> 
>> Hi,
>> 
>> I would have expected that the following code reports an error, because
>> of ambiguous function overloads:
>> 
>> infix operator ***: MultiplicationPrecedence
>> infix operator +++: AdditionPrecedence
>> 
>> func ***(x: Int, y: Int) -> String {
>> 	print("f1")
>> 	return ""
>> }
>> 
>> func ***(x: Int, y: Int) -> Int {
>> 	print("f2")
>> 	return 0
>> }
>> 
>> func +++(x: String, y: Int) -> Int {
>> 	print("f3")
>> 	return 0
>> }
>> 
>> func +++(x: Int, y: Int) -> Int {
>> 	print("f4")
>> 	return 0
>> }
>> 
>> let result = 0 *** 4 +++ 0		// prints f2 and f4
>> 
>> 
>> As far as I can tell, there are two possible overload resolutions: f1 + f3 or f2 + f4.
>> I thought that these two solutions get an "equivalent score" and therefore there would
>> be a compile error. However, that's not the case. Instead, the type checker picks
>> f2 and f4.
>> 
>> So, I guess my question is, whether there is some rule, that prefers
>> operators, which have the same argument types and the same return type
>> or whether this is simply a bug.
>> 
>> Thanks and best regards,
>> Toni
>> _______________________________________________
>> swift-users mailing list
>> swift-users at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-users
> 

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