[Issue 12710] New: Bad @nogc requirement for Windows callbacks

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12710

          Issue ID: 12710
           Summary: Bad @nogc requirement for Windows callbacks
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: regression
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: thecybershadow at gmail.com

////////////////////// test.d /////////////////////
import core.sys.windows.windows;

extern(Windows)
LRESULT wndProc(HWND, UINT, WPARAM, LPARAM) nothrow
{
    return 0;
}

void main()
{
    WNDCLASSW c;
    c.lpfnWndProc = &wndProc;
    RegisterClassW(&c);
}
///////////////////////////////////////////////////

The above no longer compiles. For some reason lpfnWndProc is now required to be
@nogc, which makes no sense, as the callback is called from within the same
thread and is allowed to interact freely with the GC.

A cast is now required, which is not very safe since the cast may subtly allow
an incorrect callback signature or calling convention.

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