inout and opApply

[Timon Gehr via Digitalmars-d]

On 23.06.2016 14:58, Steven Schveighoffer wrote:
> On 6/21/16 5:19 PM, Timon Gehr wrote:
>
>>
>> The problem here is that both variants make sense depending on context
>> and there is no syntax to distinguish between them. This proposal
>> interacts in a weird way with IFTI.
>
> I know you are probably right, but can you explain maybe via an example
> what you mean? I'm not understanding your point.
>
> -Steve

One might legitimately want to pass a inout delegate to some inout 
function and then use the delegate on data with arbitrary mutability 
qualifiers, not just inout.


The IFTI comment was about for example something like this:

struct S{
     void bar(inout int){}
     void foo(T)(T arg)inout{
         // this looks like it can be called with any argument
         arg(&bar);
     }
}

void main(){
     immutable(S) s;
     void delegate(void delegate(inout(int))) dg = x=>x(2);
     s.foo(dg); // today, this works
     // with the proposed semantics, IFTI deduces
     // T = void delegate(void delegate(inout(int)))
     // but then cannot convert dg to a T after
     // inout resolution
}

But I don't feel strongly about which of the two variants it should be. 
It's weird either way, as long as there can be only one inout in scope.