[Issue 18289] static function and access frame

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18289

--- Comment #1 from Aurelien Fredouelle <aurelien.fredouelle+dlang at gmail.com> ---
Ran into the same issue, here is some extra sample code to better understand
the problem:

template A(alias fun)
{
  void A() {
    fun();
  }
}

struct B(alias fun)
{
  static void opCall() {
    fun();
  }
}

void foo() {}

void main() {

  static void bar() {}

  void hun() {}

  A!foo(); // OK
  B!foo(); // OK

  A!bar(); // OK
  B!bar(); // OK

  A!hun(); // OK
  B!hun(); // ERROR! static function app.main.B!(hun).B.opCall cannot access
frame of function D main
}

The issue happens when instantiating the templated struct with an object that
lives on the stack of the calling function (such as the `hun` function). But it
looks like this case is not so different from the previous one (`A!hun()`),
using an eponymous function template rather than a struct with a static opCall.
Is it really expected for one case to succeed and the other to fail?

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