[clang] Add test for CWG1397

[Endill]

Summary

Resolution of this CWG breaks potential dependency loop between complete-class context of non-static data member initializer (NSDMI), and defaulted default constructor, which is noexcept depending on NSDMIs among other things.

For whatever reason in C++11 mode we issue an additional note and a different line number for the primary error. But I find the message itself even worse than aforementioned issues. It describes what's going on, but doesn't say what's bad about it. I find the previous version of this message more clear: https://github.com/llvm/llvm-project/commit/8dbc6b26171167b8ddf66a5f4b6d6fb9baf28336

[shafik]

LGTM

[shafik]

clang/test/CXX/drs/dr13xx.cpp

488

These diagnostic are pretty bad, maybe provide a comment above explaining them a little better or maybe better refactor the diagnostic?

[Endill]

Thank you for the review!

clang/test/CXX/drs/dr13xx.cpp

488

Totally agree about diagnostic not being accessible. I filed a bug for that, but not sure how to refactor it.

I don't think it's a good place to explain complicated diagnostic messages, though. If someone is interested enough, intent could be seen on this review and in CWG1397 itself. We better just fix the diagnostic, and expected message together with it.

clang/test/CXX/drs/dr13xx.cpp

#if __cplusplus >= 201103L
   template <typename T> void f(T);
   void h(int i) {
     // This is made ambiguous by dr692, but made valid again by dr1395.
     f(&i);
   }
 #endif
 }
 
+namespace dr1397 { // dr1397: 3.2
+#if __cplusplus >= 201103L
+struct A {       // #dr1397-struct-A
+  void *p = A{}; // #dr1397-void-p
+#if __cplusplus == 201103L
+  // expected-error@#dr1397-struct-A {{default member initializer for 'p' needed within definition of enclosing class 'A' outside of member functions}}
+  // expected-note@#dr1397-void-p {{in evaluation of exception specification for 'dr1397::A::A' needed here}}
+  // expected-note@#dr1397-void-p {{default member initializer declared here}}
+#elif __cplusplus >= 201402L
+  // expected-error@#dr1397-void-p {{default member initializer for 'p' needed within definition of enclosing class 'A' outside of member functions}}
+  // expected-note@#dr1397-void-p {{default member initializer declared here}}
+#endif
+  operator void*() const { return nullptr; }
+};
+#endif
+} // namespace dr1397
+
 namespace dr1399 { // dr1399: dup 1388
   template<typename ...T> void f(T..., int, T...) {} // expected-note {{candidate}} expected-error 0-1{{C++11}}
   void g() {
     f(0);
     f<int>(0, 0, 0);
     f(0, 0, 0); // expected-error {{no match}}
   }
 }

clang/www/cxx_dr_status.html

<tr id="1396">
     <td>DRWP</td>
     <td>Deferred instantiation and checking of non-static data member initializers</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="1397">
     <td><a href="https://cplusplus.github.io/CWG/issues/1397.html">1397</a></td>
     <td>CD4</td>
     <td>Class completeness in non-static data member initializers</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="full" align="center">Clang 3.2</td>
   </tr>
   <tr id="1398">
     <td><a href="https://cplusplus.github.io/CWG/issues/1398.html">1398</a></td>
     <td>CD3</td>
     <td>Non-type template parameters of type <TT>std::nullptr_t</TT></td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="1399">