Expected or Bug? struct range unmodified after foreach

[Jonathan M Davis]

On Sunday, November 06, 2011 23:26:02 Jesse Phillips wrote:
> I'm sure if this was changed there would be other interesting behavior,
> such as arrays being consumed. And suggestions other than
> 
>     for(S s; !s.empty, s.popFront())...
> 
> Example:
> 
>     void main() {
>         S s;
> 
>         foreach(i; s) {
>             assert(i == s.popCount); // Fail
>         }
> 
>         assert(s.popCount == 10); // Fail
>     }
> 
>     struct S {
>         size_t popCount;
> 
>         auto empty() {
>             if(popCount > 9)
>                 return true;
>             return false;
>         }
>         auto front() { return popCount; }
>         auto popFront() {
>             popCount++;
>         }
>     }

I'd say that it's expected. Stuff isn't normally consumed by foreach iterating 
over it - an exception would be a class which is a range, but since it's a 
reference, copying it is a shallow copy, unlike with a struct, and my guess 
would be that s is being copied when it's passed to the foreach. If it 
_wasn't_ copied like this, then passing a range to foreach would consume it 
unless you explicitly sliced it or saved it, which would probably break a lot 
of code.

- Jonathan M Davis