Things that make writing a clean binding system more difficult

[Manu via Digitalmars-d]

On 29 July 2016 at 16:51, Jonathan M Davis via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On Friday, July 29, 2016 08:29:19 Timon Gehr via Digitalmars-d wrote:
>> On 29.07.2016 06:52, Jonathan M Davis via Digitalmars-d wrote:
>> > On Friday, July 29, 2016 06:44:16 Timon Gehr via Digitalmars-d wrote:
>> >> My parser accepts the following:
>> >>
>> >> int function(int,int)ref functionPointer;
>> >>
>> >> I wasn't really aware that this was illegal in DMD. (Other function
>> >> attributes, such as pure, are accepted.)
>> >>
>> >> In fact, even the following is disallowed:
>> >> int foo(int)ref{}
>> >>
>> >>
>> >> Should I file an enhancement request?
>> >
>> > Except that ref isn't a function attribute.
>>
>> Yes it is.
>>
>> int x;
>> ref{
>>      int foo(){ return x;}
>> }
>> pragma(msg, typeof(&foo()));
>
> That's downright bizzarre given that ref applies to the return type and not
> to the this pointer (and that function doesn't even have a this pointer,
> since it's not a member function).
>
>> > It's an attribute on the return type.
>>
>> There is no such thing. Types cannot have attributes.
>
> Sure they can. e.g.
>
> auto func(ref int param) {...}
>
> The same with in and out. They apply to the type of the parameter without
> actually being part of it.
>
>> > So, it doesn't make sense for it to be on the right. That would be
>> > like having the const on the right-hand side of a member function apply to
>> > the return type rather than the function itself.
>> > ...
>>
>> You have it backwards.
>
> It looks to me like the compiler is treating ref in a schizophrenic manner
> given that when it's used on a parameter, it treats it as part of the
> parameter, whereas with the return type, it's treating it as a function
> attribute instead of associating it with the return type. I'd guess that
> that stems from the fact that while ref is really supposed to be associated
> with the type, it's not actually part of the type.

Bingo! But it's much deeper than that. ref is a disaster. Use it to
any real extent; in particular, binding (or fabricating bindings) to
extern(C++) code, and you will see just how fast it breaks down in the
most horrific of ways (almost always resulting in text mixin). I would
fork D just to fix ref!