DIP 1020--Named Parameters--Community Review Round 1

[Yuxuan Shui]

On Monday, 8 April 2019 at 13:31:48 UTC, bauss wrote:
> On Monday, 8 April 2019 at 10:10:14 UTC, Yuxuan Shui wrote:
>> On Sunday, 7 April 2019 at 21:19:20 UTC, Walter Bright wrote:
>>> On 4/7/2019 10:14 AM, Yuxuan Shui wrote:
>>>> this proposal seems to mandate the inclusion of parameter 
>>>> names in mangled name of functions.
>>>
>>> Nope.
>>
>> OK, I probably misunderstood, but what happens in the 
>> following case?
>>
>> void fun(int a, int b) {...}
>> void fun(int c, int d) {...}
>>
>> fun(c:1, d:1);
>>
>>
>> Is it ambiguous? Or does it invoke the second function? If the 
>> latter, then you have to include the parameter names in 
>> mangled name.
>
> That wouldn't work because the compiler would reject your 
> function definitions when you attempt to call either of them 
> because they're ambiguous.
>
> Just like it is today.
>
> Basically you could look at them just being:
>
> void fun(int,int);
> void fun(int,int);
>
> When you call a function like:
>
> void fun(int a, int b);
>
> ...
>
> fun(a: 1, b: 2);
>
> the compiler would really just reorder the passed values to 
> match the parameters (If they can be specified in any order, if 
> not then it will just them as it is.
>
> Which means:
>
> fun(a: 1, b: 2);
>
> becomes:
>
> fun(1, 2);
>
> and by then it should be clear why it wouldn't be allowed nor 
> would work at all.

Yes, what you said _could_ be the case. But it's not immediately 
clear from Walter's proposal, that's why I would prefer a direct 
answer from him.

Quoting from Walter's proposal:

> I.e. function resolution is done by constructing an argument 
> list separately for each function before testing it for 
> matching. Of course, if the parameter name(s) don't match, the 
> function doesn't match.

 From that, it sounds like fun(c:1,d:1) shouldn't match fun(int a, 
int b). That's why I asked that question.

The interpretation of his proposal suggested by you (i.e. this 
call is ambiguous) is obviously a possible one, but not 
necessarily what Walter intended.