[clang] Add tests for CWG issues 977, 1482, 2516

[Endill]

Summary

CWG977 focus on point of /completeness/ of enums. Wording provided in CWG1482.
CWG1482 and CWG2516 focus on locus (point) of /declaration/. Wording provided in CWG2516.

[shafik]

LGTM

[thakis]

This breaks check-clang on windows: http://45.33.8.238/win/78827/step_7.txt

Please take a look and revert for now if it takes a while to fix.

[Endill]

In D151042#4364108, @thakis wrote:

This breaks check-clang on windows: http://45.33.8.238/win/78827/step_7.txt

Please take a look and revert for now if it takes a while to fix.

It's not hard to fix, but is it just windows? Sorry I'm not too familiar with buildbots.

[thakis]

On my bots (which cover linux, mac/arm, and windows), it's only failing on the windows bot.

[Endill]

All tests pass for me on Linux.
As far as I understand, diagnostics on Windows are not supposed to be different given the same -cc1 flags. Reverting for further investigation.

[thakis]

In D151042#4364131, @Endill wrote:

All tests pass for me on Linux.
As far as I understand, diagnostics on Windows are not supposed to be different given the same -cc1 flags. Reverting for further investigation.

Thanks for the revert. The test also failed on the official llvm win buildbot here https://lab.llvm.org/buildbot/#/builders/123 fwiw (but it takes a long time to load).

Diagnostics on windows absolutely can be different on windows with the same cc1 flags. Clang uses the host system's target triple, and for (say) x86_64-pc-windows clang runs in MS mode, which enables some cl.exe compatibility things.

In fact, you can probably repro the test failure on your linux box if you change that test and add locally add -triple=i386-pc-win32 to the RUN line (or maybe the behavior to enable MS extensions based on target lives in the driver; in that case you'd have to add -fms-extensions -fms-compatibility).

[Endill]

In D151042#4364149, @thakis wrote:

In fact, you can probably repro the test failure on your linux box if you change that test and add locally add -triple=i386-pc-win32 to the RUN line

You're right, MSVC-specific triple make the issue reproduce on my Linux box. Thank you!

clang/test/CXX/drs/dr14xx.cpp

#endif
   } // namespace StringLiterals
 #endif
 } // dr1467
 
 namespace dr1479 { // dr1479: yes
   int operator"" _a(const char*, std::size_t = 0); // expected-error {{literal operator cannot have a default argument}}
 }
 
+namespace dr1482 { // dr1482: yes
+                   // NB: sup 2516, test reused there
+#if __cplusplus >= 201103L
+template <typename T> struct S {
+  typedef char I;
+};
+enum E2 : S<E2>::I { e };
+// expected-error@-1 {{use of undeclared identifier 'E2'}}
+#endif
+} // namespace dr1482
+
 namespace dr1490 {  // dr1490: 3.7 c++11
   // List-initialization from a string literal
 
   char s[4]{"abc"};                   // Ok
   std::initializer_list<char>{"abc"}; // expected-error {{expected unqualified-id}}}
 } // dr1490
 
 namespace dr1495 { // dr1495: 4

clang/test/CXX/drs/dr25xx.cpp

 // RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown %s -verify
 
+namespace dr2516 { // dr2516: yes
+                   // NB: reusing 1482 test
+#if __cplusplus >= 201103L
+template <typename T> struct S {
+  typedef char I;
+};
+enum E2 : S<E2>::I { e };
+// expected-error@-1 {{use of undeclared identifier 'E2'}}
+#endif
+} // namespace dr2516
+
 namespace dr2518 { // dr2518: 17
 
 template <class T>
 void f(T t) {
   if constexpr (sizeof(T) != sizeof(int)) {
     static_assert(false, "must be int-sized"); // expected-error {{must be int-size}}
   }
 }

clang/test/CXX/drs/dr9xx.cpp

 namespace dr974 { // dr974: yes
 #if __cplusplus >= 201103L
   void test() {
     auto lam = [](int x = 42) { return x; };
   }
 #endif
 }
 
+namespace dr977 { // dr977: yes
+enum E { e = E() };
+// expected-error@-1 {{invalid use of incomplete type 'E'}}
+// expected-note@-2 {{definition of 'dr977::E' is not complete until the closing '}'}}
+#if __cplusplus >= 201103L
+enum E2 : int { e2 = E2() };
+enum struct E3 { e = static_cast<int>(E3()) };
+enum struct E4 : int { e = static_cast<int>(E4()) };
+#endif
+} // namespace dr977
+
 namespace dr990 { // dr990: 3.5
 #if __cplusplus >= 201103L
   struct A { // expected-note 2{{candidate}}
     A(std::initializer_list<int>); // expected-note {{candidate}}
   };
   struct B {
     A a;
   };

clang/www/cxx_dr_status.html

<tr id="976">
     <td>CD2</td>
     <td>Deduction for <TT>const T&amp;</TT> conversion operators</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="977">
     <td><a href="https://cplusplus.github.io/CWG/issues/977.html">977</a></td>
     <td>CD3</td>
     <td>When is an enumeration type complete?</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="full" align="center">Yes</td>
   </tr>
   <tr id="978">
     <td><a href="https://cplusplus.github.io/CWG/issues/978.html">978</a></td>
     <td>CD2</td>
     <td>Incorrect specification for copy initialization</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="979">
<tr id="1481">
     <td>CD3</td>
     <td>Increment/decrement operators with reference parameters</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="1482">
     <td><a href="https://cplusplus.github.io/CWG/issues/1482.html">1482</a></td>
     <td>CD3</td>
     <td>Point of declaration of enumeration</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="full" align="center">Yes</td>
   </tr>
   <tr id="1483">
     <td><a href="https://cplusplus.github.io/CWG/issues/1483.html">1483</a></td>
     <td>NAD</td>
     <td>Non-dependent <I>static_assert-declaration</I>s</td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="1484">
<tr class="open" id="2515">
     <td>open</td>
     <td>Result of a function call</td>
     <td align="center">Not resolved</td>
   </tr>
   <tr id="2516">
     <td><a href="https://cplusplus.github.io/CWG/issues/2516.html">2516</a></td>
     <td>DR</td>
     <td>Locus of <I>enum-specifier</I> or <I>opaque-enum-declaration</I></td>
-    <td class="none" align="center">Unknown</td>
+    <td class="full" align="center">Yes</td>
   </tr>
   <tr id="2517">
     <td><a href="https://cplusplus.github.io/CWG/issues/2517.html">2517</a></td>
     <td>DR</td>
     <td>Useless restriction on use of parameter in <I>constraint-expression</I></td>
     <td class="none" align="center">Unknown</td>
   </tr>
   <tr id="2518">