DIP66 1.2 (Multiple) alias this. Continuation of work.

[Timon Gehr via Digitalmars-d]

On 05/26/2015 01:17 AM, IgorStepanov wrote:
>
>
> My example:
> auto foo(T)(){ return 1; }
> auto foo(T)()if(is(T: int)){ return 2; }
>
> struct Foo
> {
>      //...
> }
> struct Bar
> {
>       Foo f;
>       int i;
>       alias i this;
> }
>
> auto ret = foo!Bar;
> assert(ret == 2); //exactly the second function
> ...

(No, this actually raises an ambiguity error, but I see the point.)

> After that, imagine, someone added alias intVal this to Foo.
> Now there are many ways to convert Bar to int. However, user
> don't know about it.
>
> And if foo!Bar will start to return 1, it is very ugly situation.

I'm not convinced the alternative is better.

One can still do e.g.:

auto foo(T)()if(!is(typeof({static assert(is(T: int));}))){ return 1; }
auto foo(T)()if(is(typeof({static assert(is(T: int));}))){ return 2; }