DIP23 draft: Fixing properties redux

[Andrei Alexandrescu]

On 2/4/13 12:53 AM, kenji hara wrote:
> If the expression is generated from string mixin, might have a problem.
>
> // This is much simple case. Real example might be more complicated.
> template AddressOf(string exp)
> {
>      enum AddressOf = "&" ~ exp;
> }
> struct S {
>      @property int prop() { return 1; }
> }
> void main() {
>      S s;
>      assert(s.prop == 1);
>      int* p = mixin(AddressOf!("s.prop"));  // &s.prop returns delegate
> }
>
> I think that parenthesis-dependent syntax is not good.
>
> Kenji Hara

Couldn't AddressOf use "&(" + exp + ")"?

I thought more about this. The problem remains even without @property, 
due to optional parens in function invocation. Consider:

ref int fun() { ... }
auto p1 = &fun;
auto p2 = &(fun);
auto p3 = &(fun());

What are the types of the three? The optional parens in invocation 
require some disambiguation. I think the sensible disambiguation is to 
have &fun take the address of fun and the other two take the address of 
fun's result.

I would agree restricting the properties, but requiring a __trait to 
take the address of a regular function or method seems overkill.


Andrei