[clang] [clang] Add test for CWG 2006 and update status (PR #215259)

[Shengxin Pei via cfe-commits]

https://github.com/TPPPP72 updated https://github.com/llvm/llvm-project/pull/215259

>From ec5fb83e47a90025479f387a5b4beb73e5981742 Mon Sep 17 00:00:00 2001
From: Shengxin Pei <TPPPP72 at outlook.com>
Date: Tue, 11 Aug 2026 00:20:46 +0800
Subject: [PATCH 1/3] [clang] Add test for CWG 2006 and update status

---
 clang/test/CXX/drs/cwg20xx.cpp | 83 ++++++++++++++++++++++++++++++++++
 clang/www/cxx_dr_status.html   |  2 +-
 2 files changed, 84 insertions(+), 1 deletion(-)

diff --git a/clang/test/CXX/drs/cwg20xx.cpp b/clang/test/CXX/drs/cwg20xx.cpp
index 75b4094283db0..13286ef446325 100644
--- a/clang/test/CXX/drs/cwg20xx.cpp
+++ b/clang/test/CXX/drs/cwg20xx.cpp
@@ -11,6 +11,89 @@
 // cxx98-error at -1 {{variadic macros are a C99 feature}}
 #endif
 
+namespace std { class type_info; }
+namespace cwg2006 { // cwg2006: 2.7
+  void test_object_pointer(const void *cp, volatile void *vp, const volatile void *cvp) {
+    (void)static_cast<const void*>(cp);
+    (void)static_cast<volatile void*>(vp);
+    (void)static_cast<const volatile void*>(cvp);
+
+    int x = 0;
+    const int cx = 0;
+    const void *p1 = &x;
+    const void *p2 = &cx;
+    (void)p1;
+    (void)p2;
+  }
+
+  void test_cast(int x) {
+    (const void)x;
+    (volatile void)x;
+    (const volatile void)x;
+  }
+
+  const void get_const_void()
+#if __cplusplus >= 201103L
+    noexcept
+#endif
+  {}
+
+  volatile void get_volatile_void()
+#if __cplusplus >= 201103L
+    noexcept
+#endif
+  {}
+  // since-cxx20-warning at -5 {{volatile-qualified return type 'volatile void' is deprecated}}
+
+  const volatile void get_cv_void()
+#if __cplusplus >= 201103L
+    noexcept
+#endif
+  {}
+  // since-cxx20-warning at -5 {{volatile-qualified return type 'const volatile void' is deprecated}}
+
+  void test_return() {
+    return get_const_void();
+  }
+
+  void test_return_volatile() {
+    return get_volatile_void();
+  }
+
+  void test_return_cv() {
+    return get_cv_void();
+  }
+
+  void test_conditional(bool b) {
+    b ? get_const_void() : get_const_void();
+    b ? get_volatile_void() : get_const_void();
+    b ? get_cv_void() : get_const_void();
+  }
+
+  namespace std { class type_info; }
+  void test_typeid() {
+    (void)typeid(const void);
+    (void)typeid(volatile void);
+    (void)typeid(const volatile void);
+  }
+
+#if __cplusplus >= 201103L
+  template <typename T, typename U>
+  struct is_same { static constexpr bool value = false; };
+
+  template <typename T>
+  struct is_same<T, T> { static constexpr bool value = true; };
+
+  void test_cxx11() {
+    decltype(get_const_void()) *p = nullptr;
+    static_assert(noexcept(get_const_void()), "");
+
+    using CommonType = decltype(true ? get_const_void() : get_volatile_void());
+    static_assert(is_same<CommonType, void>::value, "");
+  }
+#endif
+} // namespace cwg2006
+
 namespace cwg2007 { // cwg2007: 3.4
 template<typename T> struct A { typename T::error e; };
 template<typename T> struct B { };
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 4d29e6b4b32f4..40cac7f440832 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -13831,7 +13831,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td>[<a href="https://wg21.link/basic.compound">basic.compound</a>]</td>
     <td>CD4</td>
     <td>Cv-qualified <TT>void</TT> types</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="full" align="center">Clang 2.7</td>
   </tr>
   <tr id="2007">
     <td><a href="https://cplusplus.github.io/CWG/issues/2007.html">2007</a></td>

>From a4eb6481014f46642aeeb88e4e7d8ed2e7df7e86 Mon Sep 17 00:00:00 2001
From: Shengxin Pei <TPPPP72 at outlook.com>
Date: Tue, 11 Aug 2026 00:37:27 +0800
Subject: [PATCH 2/3] remove an extra line

---
 clang/test/CXX/drs/cwg20xx.cpp | 1 -
 1 file changed, 1 deletion(-)

diff --git a/clang/test/CXX/drs/cwg20xx.cpp b/clang/test/CXX/drs/cwg20xx.cpp
index 13286ef446325..45cf69c850dba 100644
--- a/clang/test/CXX/drs/cwg20xx.cpp
+++ b/clang/test/CXX/drs/cwg20xx.cpp
@@ -70,7 +70,6 @@ namespace cwg2006 { // cwg2006: 2.7
     b ? get_cv_void() : get_const_void();
   }
 
-  namespace std { class type_info; }
   void test_typeid() {
     (void)typeid(const void);
     (void)typeid(volatile void);

>From 54a9b941bb061488fa9a694918444736f75137d8 Mon Sep 17 00:00:00 2001
From: Shengxin Pei <TPPPP72 at outlook.com>
Date: Tue, 11 Aug 2026 16:10:36 +0800
Subject: [PATCH 3/3] use __is_same

---
 clang/test/CXX/drs/cwg20xx.cpp | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/clang/test/CXX/drs/cwg20xx.cpp b/clang/test/CXX/drs/cwg20xx.cpp
index 45cf69c850dba..0f5622f4734c8 100644
--- a/clang/test/CXX/drs/cwg20xx.cpp
+++ b/clang/test/CXX/drs/cwg20xx.cpp
@@ -77,18 +77,12 @@ namespace cwg2006 { // cwg2006: 2.7
   }
 
 #if __cplusplus >= 201103L
-  template <typename T, typename U>
-  struct is_same { static constexpr bool value = false; };
-
-  template <typename T>
-  struct is_same<T, T> { static constexpr bool value = true; };
-
   void test_cxx11() {
     decltype(get_const_void()) *p = nullptr;
     static_assert(noexcept(get_const_void()), "");
 
     using CommonType = decltype(true ? get_const_void() : get_volatile_void());
-    static_assert(is_same<CommonType, void>::value, "");
+    static_assert(__is_same(CommonType, void), "");
   }
 #endif
 } // namespace cwg2006