Operator overloading through UFCS doesn't work

[Tommi]

On Sunday, 14 October 2012 at 07:14:25 UTC, Maxim Fomin wrote:
> If this request is approved and compiler has opUnary definition 
> outside type (which suits better then alias
> this) such function would hijack alias this.

Free functions cannot and must not ever hijack, i.e. modify 
existing functionality of a type. Free functions should only be 
able to add new functionality to a type. This is what currently 
happens with alias this vs free function which is accessed 
through UFCS:

struct B
{
     void fun()
     {
         writeln("B.fun()");
     }
}

struct A
{
     B b;
     alias b this;
}

void fun(A a)
{
     writeln(".fun(A)");
}

void main()
{
     A a;
     a.fun(); // prints B.fun() as it should
}

It shouldn't be any different if fun was some operator function, 
like opUnary; the free function mustn't hijack type A's existing 
functionality (which is currently being provided to A by that 
alias this thingy).