Why does BinaryHeap sometime cause compile-error in foeach?

[user1234]

On Saturday, 30 September 2017 at 09:27:23 UTC, Shigeki Karita 
wrote:
> https://dpaste.dzfl.pl/cd605899d050
>
> why this code cannot convert to foreach (over Structs and 
> Classes with Ranges).
>
>     auto h = new BinaryHeap!(int[])(new int[0]);
>     typeof(h).stringof.writeln;
>     static assert(isInputRange!(typeof(h)));
>     h.insert(3);
>     h.insert(1);
>     h.insert(2);
>     // Error: invalid foreach aggregate `h`
>     // foreach (e; h) e.writeln;
>     for (; !h.empty; h.popFront()) {
>       auto e = h.front();
>       e.writeln;
>     }
>
>
> https://dlang.org/spec/statement.html#foreach-with-ranges

The reason why it doesn't work is much more simple than you 
think: h is not a BinaryHeap, it's a pointer to.

Try "foreach (e; *h) e.writeln;" and it works.