"instanceOf" trait for conditional implementations

[monarch_dodra]

On Thursday, 4 October 2012 at 12:48:51 UTC, so wrote:
> On Thursday, 4 October 2012 at 09:43:08 UTC, monarch_dodra 
> wrote:
>
>> The current implementation for "isAssignable" is
>> //----
>> template isAssignable(Lhs, Rhs)
>> {
>>    enum bool isAssignable = is(typeof({
>>        Lhs l = void;
>>        void f(Rhs r) { l = r; }
>>        return l;
>>    }));
>> }
>
> OT - Is there any reason for disabling UFCS for this?
>
> template isAssignable(Lhs, Rhs)
> {
>     enum bool isAssignable =
>     {
>         Lhs l = void;
>         void f(Rhs r) { l = r; }
>         return l;
>     }.typeof.is;
> }

Because typeof is a keyword, and is is a declaration.

There are two open ER to allow typeof to be used as a property: 
While not strictly EFCS, it would be convenient.

Regarding is, There are no open requests. But I guess it would be 
fun to write
if( T.is(U) ).

But where would it end? Make if UFCS too?
T.is(U).if()

IMO, I can see typeof being a property, but not is.