DIP66 - Multiple alias this

[IgorStepanov via Digitalmars-d]

On Friday, 10 October 2014 at 22:18:36 UTC, Timon Gehr wrote:
> On 10/11/2014 12:07 AM, IgorStepanov wrote:
>> On Friday, 10 October 2014 at 21:25:17 UTC, Walter Bright 
>> wrote:
>>>
>>> If 'a' and 'b' both contain overloads for function foo, then 
>>> it should
>>> behave like imports do (which is a bit complex).
>>
>> Hmm. Now it works as I wrote it DIP pseudo-code:
>
> The pseudo-code doesn't actually specify that the arguments the 
> identifier is being called with are considered at all.
>
>> struct A
>> {
>>     void foo(string);
>>     void foo(int);
>> }
>>
>> struct B
>> {
>>     void foo(double);
>> }
>>
>> struct C
>> {
>>     A a;
>>     B b;
>>     alias a this;
>>     alias b this;
>> }
>>
>> C.foo("test"); //found only one acceptable foo: C.a.foo(string)
>> C.foo(5);      //1. Check a: found C.a.foo(int);
>>                //2. Check b: found C.b.foo(double);
>>                //3. Raise error: C.a.foo(int) vs 
>> C.b.foo(double) conflict
>> C.foo(5.0);    //found only one acceptable foo: C.b.foo(double)
>>
>> Is it Ok?
>> ...
>
> That is the right behaviour. What happens in this case:
>
> struct A{
>     void foo(int);
>     void foo(double);
> }
>
> struct B
>     void foo(string);
> }
>
> ... // (struct C and calls as yours)

C.foo("test"); //Ok, C.b.foo(string);
C.foo(5);      //Ok, C.a.foo(int);
C.foo(5.0);    //Ok, C.a.foo(double);

Compiler simply tries to forward c.foo(ARG) -> c.a.foo(ARG) and 
c.b.foo(ARG). If only one is correct, compiler will accept it. If 
both is correct, compiler will raise an error.