Bug 10843 – Combinatorial problem of struct & alias this & null

These tree samples don't work: ------------------ unittest { static struct HANDLE { void* h; alias h this; } //HANDLE a = null; // NG HANDLE a; a = null; // OK } unittest { static struct HANDLE { void* h; alias h this; this(void* h) { this.h = h; } } HANDLE a = null; // OK static void foo(HANDLE h){} //foo(null); // NG } unittest { static struct HANDLE { void* h; alias h this; this(void* h) { this.h = h; } } static struct WSAEVENT { HANDLE h; alias h this; this(HANDLE h) { this.h = h; } } auto a = cast(HANDLE)null; // OK //auto b = cast(WSAEVENT)null; // NG }

This is invalid report in all there cases. 1) is implicit construction for which constructor with respective arguments should be defined (as provided in second example). 2) is implicit construction on argument passing for which variardic functions do exists. Spec is explicit that for such cases ctor is required. 3) same as #2 with difference that now function is a ctor This is compilable: unittest { static struct HANDLE { void* h; alias h this; } //HANDLE a = null; // NG HANDLE a; a = null; // OK } unittest { static struct HANDLE { void* h; alias h this; this(void* h) { this.h = h; } } HANDLE a = null; // OK static void foo(HANDLE h ...){} foo(null); // OK } unittest { static struct HANDLE { void* h; alias h this; this(void* h) { this.h = h; } } static struct WSAEVENT { HANDLE h; alias h this; this(HANDLE h ...) { this.h = h; } } auto a = cast(HANDLE)null; // OK auto b = cast(WSAEVENT)null; // OK } void main() {}