[Issue 16705] [REG2.069] TaskPool.reduce fails to compile "cannot get frame pointer to D main"

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=16705

--- Comment #13 from Ajieskola at gmail.com ---
Simplified test case of the issue itself:

```d
void main()
{   import std.parallelism;

    struct MyIota
    { size_t front;
      void popFront(){front++;}
      auto empty(){return front >= 100;}
      auto opIndex(size_t i){return front+i;}
      auto length(){return 100-front;}
    }

    auto mySum = taskPool.reduce!"a + b"(MyIota());
}
```

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