Re: pure opApply

[Steven Schveighoffer via Digitalmars-d-learn]

On 3/31/16 6:23 AM, Q. Schroll wrote:
Simple as that, shouldn't this work?
struct X
{
     int opApply(int delegate(string) dg)
     {
         return dg("impure");
     }

     int opApply(int delegate(string) pure dg) pure
     {
         return dg("pure");
     }
}

void main()
{
     X x;
     string result;

     x.opApply(
         (string s)
         {
             result = s;
             return 0;
         }
     );
     writeln(result); // does compile and prints "pure".

     x.opApply(
         (string s)
         {
             result = s;
             write("");
             return 0;
         }
     );
     writeln(result); // does compile and prints "impure".

     /+ (1)
     foreach (string s; x)
     {
         result = s;
     }
     writeln(result); // does not compile: x.opApply matches more than
one declaration
     +/
     /+ (2)
     foreach (string s; x)
     {
         result = s;
         write("");
     }
     writeln(result); // does not compile: x.opApply matches more than
one declaration
     +/
}

Can someone explain me, why the compiler cannot resolve the right
opApply? From what I know, it generates a delegate with inferred pure
attribute and looks for the best match of opApply. Why does the manual
rewrite work? If I've done the rewrite improperly, please tell me.

I think it's a bug. foreach and opApply are specially coded in the 
compiler I think, so there's bound to be inconsistencies between them 
and normal overload rules.

-Steve