Re: 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; }