[clang] Add test for CWG952

[Endill]

Summary

P1787: CWG952 is resolved by refining the definition of “naming class” per Richard’s suggestion in “CWG1621 and [class.static/2”.
Wording:

• [class.static]/2 removed;
• [class.access.base]/5 rephrased.

Currently behavior is the following: unqualified names undergo unqualified name lookup [1], which perform unqualified search in immediate scope [2]. This scope is the scope the definition of naming class [3] refers to. A::I is not accessible when named in classes C and D per [3]. In particular, the last item regarding base class ([class.access.base]/5.4) is not applicable, because class A is not accessible in both classes C and D per [4].

References:

1. basic.lookup.unqual/4
2. basic.lookup.unqual/3
3. class.access.base/5
4. class.access.base/4

[erichkeane]

This appears right to me! I'd like others to take a look though.

[aaron.ballman]

LGTM, though I would appreciate another test (that I expect to pass).

clang/test/CXX/drs/dr9xx.cpp

76

I wouldn't mind another test case:

struct A {
protected:
  static int x;
};
struct B : A {
  friend int get(B) { return x; }
};

this was something Richard had pointed out needs to still work as part of the reflector discussions of this issue.

[Endill]

clang/test/CXX/drs/dr9xx.cpp

76

Sorry, it seems I missed your comment when I landed the patch. Would it be fine to add this test as NFC patch?

clang/test/CXX/drs/dr9xx.cpp

 // RUN: %clang_cc1 -std=c++98 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++11 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++14 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
-// RUN: %clang_cc1 -std=c++1z %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
-
-#if __cplusplus < 201103L
-// expected-no-diagnostics
-#endif
+// RUN: %clang_cc1 -std=c++17 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++20 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++2b %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
 
 namespace std {
   __extension__ typedef __SIZE_TYPE__ size_t;
 
   template<typename T> struct initializer_list {
     const T *p; size_t n;
     initializer_list(const T *p, size_t n);
   };
void f() {
      if (constexpr A i = 101) { }
      switch (constexpr A i = 2) { default: break; case 2: break; }
      for (; constexpr A i = 0; ) { }
      while (constexpr A i = 0) { }
   }
 #endif
 }
 
+namespace dr952 { // dr952: yes
+struct A {
+  typedef int I; // #dr952-typedef-decl
+};
+struct B : private A { // #dr952-inheritance
+};
+struct C : B {
+  void f() {
+    I i1; // expected-error {{private member}}
+    // expected-note@#dr952-inheritance {{constrained by private inheritance}}
+    // expected-note@#dr952-typedef-decl {{declared here}}
+  }
+  I i2; // expected-error {{private member}}
+  // expected-note@#dr952-inheritance {{constrained by private inheritance}}
+  // expected-note@#dr952-typedef-decl {{declared here}}
+  struct D {
+    I i3; // expected-error {{private member}}
+    // expected-note@#dr952-inheritance {{constrained by private inheritance}}
+    // expected-note@#dr952-typedef-decl {{declared here}}
+    void g() {
+      I i4; // expected-error {{private member}}
+      // expected-note@#dr952-inheritance {{constrained by private inheritance}}
+      // expected-note@#dr952-typedef-decl {{declared here}}
+    }
+  };
+};
+} // namespace dr952
+
 namespace dr974 { // dr974: yes
 #if __cplusplus >= 201103L
   void test() {
     auto lam = [](int x = 42) { return x; };
   }
 #endif
 }

clang/www/cxx_dr_status.html

<tr id="951">
     <td>CD2</td>
     <td>Problems with <I>attribute-specifier</I>s</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="952">
     <td><a href="https://wg21.link/cwg952">952</a></td>
     <td>CD6</td>
     <td>Insufficient description of &#8220;naming class&#8221;</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="full" align="center">Yes</td>
   </tr>
   <tr id="953">
     <td><a href="https://wg21.link/cwg953">953</a></td>
     <td>CD2</td>
     <td>Rvalue references and function viability</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr class="open" id="954">