Allow locale{nullptr} to compile (#4245)

Author: StephanTLavavej

stl/inc/xlocale

@@ -226,7 +226,7 @@ public:
         _Newimp->_Addfac(_Facptr, _Facet::id);
         _Newimp->_Catmask = none;
         _Newimp->_Name    = "*";
-        return locale{_Newimp};
+        return locale{_Secret_locale_construct_tag{}, _Newimp};
     }
 
     template <class _Facet>
@@ -391,7 +391,11 @@ public:
     static _MRTIMP2_PURE locale __CLRCALL_PURE_OR_CDECL empty(); // empty (transparent) locale
 
 private:
-    locale(_Locimp* _Ptrimp) : _Ptr(_Ptrimp) {}
+    struct _Secret_locale_construct_tag {
+        explicit _Secret_locale_construct_tag() = default;
+    };
+
+    explicit locale(_Secret_locale_construct_tag, _Locimp* _Ptrimp) : _Ptr(_Ptrimp) {}
 
     static _MRTIMP2_PURE _Locimp* __CLRCALL_PURE_OR_CDECL _Init(bool _Do_incref = false); // initialize locale
     static _MRTIMP2_PURE _Locimp* __CLRCALL_PURE_OR_CDECL _Getgloballocale();

stl/src/locale0.cpp

@@ -159,7 +159,7 @@ _MRTIMP2_PURE const locale& __CLRCALL_PURE_OR_CDECL locale::classic() { // get r
 
 _MRTIMP2_PURE locale __CLRCALL_PURE_OR_CDECL locale::empty() { // make empty transparent locale
     _Init();
-    return locale{_Locimp::_New_Locimp(true)};
+    return locale{_Secret_locale_construct_tag{}, _Locimp::_New_Locimp(true)};
 }
 
 _MRTIMP2_PURE locale::_Locimp* __CLRCALL_PURE_OR_CDECL locale::_Init(bool _Do_incref) { // setup global and "C" locales
@@ -176,7 +176,7 @@ _MRTIMP2_PURE locale::_Locimp* __CLRCALL_PURE_OR_CDECL locale::_Init(bool _Do_in
 
         // set classic to match
         ptr->_Incref();
-        ::new (&classic_locale) locale{ptr};
+        ::new (&classic_locale) locale{_Secret_locale_construct_tag{}, ptr};
 #if defined(_M_CEE_PURE)
         locale::_Locimp::_Clocptr = ptr;
 #else // ^^^ defined(_M_CEE_PURE) / !defined(_M_CEE_PURE) vvv