[clang] Mark CWG2009 as N/A

[Endill]

Summary

P1787: CWG2331 is resolved by defining lookup from complete-class contexts and out-of-line member definitions. The rest of CWG2009 is resolved by making it ill-formed NDR for forward lookup outside a complete-class context to change the results (before overload resolution, to avoid differences in instantiation).
Wording: The result of the search is the declaration set of S(N, T). If it is an invalid set, the program is ill-formed. If it differs from the result of a search in T for N from immediately after the class-specifier of T, the program is ill-formed, no diagnostic required. ([class.member.lookup]/7)

[shafik]

LGTM, from what I can tell this did not change anything.

clang/test/CXX/drs/dr20xx.cpp

 template<typename T> struct A { typename T::error e; };
 template<typename T> struct B { };
 B<A<void> > b1;
 B<A<void> > b2 = b1;
 int a = b2[0]; // expected-error {{does not provide a subscript operator}}
 int b = __builtin_addressof(b2)->foo; // expected-error {{no member}}
 }
 
+// dr2009: na
+
 namespace dr2026 { // dr2026: 11
   template<int> struct X {};
 
   const int a = a + 1; // expected-warning {{uninitialized}} expected-note {{here}} expected-note 0-1{{outside its lifetime}}
   X<a> xa; // expected-error {{constant expression}} expected-note {{initializer of 'a'}}
 
 #if __cplusplus >= 201103L
   constexpr int b = b; // expected-error {{constant expression}} expected-note {{outside its lifetime}}

clang/www/cxx_dr_status.html

<tr id="2008">
     <td>CD4</td>
     <td>Default <I>template-argument</I>s underspecified</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="2009">
     <td><a href="https://cplusplus.github.io/CWG/issues/2009.html">2009</a></td>
     <td>CD6</td>
     <td>Unclear specification of class scope</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="na" align="center">N/A</td>
   </tr>
   <tr id="2010">
     <td><a href="https://cplusplus.github.io/CWG/issues/2010.html">2010</a></td>
     <td>CD4</td>
     <td><I>exception-specification</I>s and conversion operators</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="2011">