[clang] Add tests for DRs about inheriting constructors (#79981)

Covers CWG issues
[1150](https://cplusplus.github.io/CWG/issues/1150.html),
[1487](https://cplusplus.github.io/CWG/issues/1487.html),
[1567](https://cplusplus.github.io/CWG/issues/1567.html),
[1738](https://cplusplus.github.io/CWG/issues/1738.html),
[2273](https://cplusplus.github.io/CWG/issues/2273.html),
[2277](https://cplusplus.github.io/CWG/issues/2277.html),
[2356](https://cplusplus.github.io/CWG/issues/2356.html),
[2504](https://cplusplus.github.io/CWG/issues/2504.html).

On top of the wording in proposed resolutions,
[P0136R1](https://wg21.link/p0136r1) "Rewording inheriting constructors
(core issue 1941 et al)" is a very relevant paper.

Note that status for 1738 `sup P0136R1` is not officially recognized by
CWG, but saying `yes` or `no` seems even more confusing to me. Official
resolution is to reject certain code, but Clang is the only
implementation that still rejects it to this day:
https://godbolt.org/z/b1W8jc1o5. GCC rejected it until 9, now it's
accepted: https://godbolt.org/z/of6oh4sdT

clang/test/CXX/drs/dr11xx.cpp

@@ -70,3 +70,5 @@ namespace dr1113 { // dr1113: partial
   }
   void g() { f(); }
 }
+
+// dr1150: na

clang/test/CXX/drs/dr14xx.cpp

@@ -614,6 +614,30 @@ enum E2 : S<E2>::I { e };
 #endif
 } // namespace dr1482
 
+namespace dr1487 { // dr1487: 3.3
+#if __cplusplus >= 201103L
+struct A { // #dr1482-A
+  struct B {
+    using A::A;
+    // since-cxx11-error@-1 {{using declaration refers into 'A::', which is not a base class of 'B'}}
+  };
+
+  struct C : A {
+  // since-cxx11-error@-1 {{base class has incomplete type}}
+  //   since-cxx11-note@#dr1482-A {{definition of 'dr1487::A' is not complete until the closing '}'}}
+    using A::A;
+    // since-cxx11-error@-1 {{using declaration refers into 'A::', which is not a base class of 'C'}}
+  };
+
+  struct D;
+};
+
+struct D : A {
+  using A::A;
+};
+#endif
+} // namespace dr1487
+
 namespace dr1490 {  // dr1490: 3.7 c++11
 #if __cplusplus >= 201103L
   // List-initialization from a string literal

clang/test/CXX/drs/dr15xx.cpp

@@ -360,6 +360,45 @@ namespace dr1563 { // dr1563: yes
 #endif
 }
 
+namespace dr1567 { // dr1567: 3.3
+#if __cplusplus >= 201103L
+struct B;
+struct A {
+  A(const A&);
+  A(const B&) = delete;
+  A(A&&);
+  A(B&&) = delete;
+  A(int); // #dr1567-A-int
+};
+
+struct B: A { // #dr1567-B
+  using A::A; // #dr1567-using-A
+  B(double); // #dr1567-B-double
+};
+
+A a{0};
+B b{1.0};
+// Good, deleted converting ctors are not inherited as copy/move ctors
+B b2{b};
+B b3{B{1.0}};
+// Good, copy/move ctors are not inherited
+B b4{a};
+// since-cxx11-error@-1 {{no matching constructor for initialization of 'B'}}
+//   since-cxx11-note@#dr1567-A-int {{candidate inherited constructor not viable: no known conversion from 'A' to 'int' for 1st argument}}
+//   since-cxx11-note@#dr1567-using-A {{constructor from base class 'A' inherited here}}
+//   since-cxx11-note@#dr1567-B {{candidate constructor (the implicit copy constructor) not viable: no known conversion from 'A' to 'const B' for 1st argument}}
+//   since-cxx11-note@#dr1567-B {{candidate constructor (the implicit move constructor) not viable: no known conversion from 'A' to 'B' for 1st argument}}
+//   since-cxx11-note@#dr1567-B-double {{candidate constructor not viable: no known conversion from 'A' to 'double' for 1st argument}}
+B b5{A{0}};
+// since-cxx11-error@-1 {{no matching constructor for initialization of 'B'}}
+//   since-cxx11-note@#dr1567-A-int {{candidate inherited constructor not viable: no known conversion from 'A' to 'int' for 1st argument}}
+//   since-cxx11-note@#dr1567-using-A {{constructor from base class 'A' inherited here}}
+//   since-cxx11-note@#dr1567-B {{candidate constructor (the implicit copy constructor) not viable: no known conversion from 'A' to 'const B' for 1st argument}}
+//   since-cxx11-note@#dr1567-B {{candidate constructor (the implicit move constructor) not viable: no known conversion from 'A' to 'B' for 1st argument}}
+//   since-cxx11-note@#dr1567-B-double {{candidate constructor not viable: no known conversion from 'A' to 'double' for 1st argument}}
+#endif
+}
+
 namespace dr1573 { // dr1573: 3.9
 #if __cplusplus >= 201103L
   // ellipsis is inherited (p0136r1 supersedes this part).

clang/test/CXX/drs/dr17xx.cpp

@@ -89,6 +89,23 @@ S s(q); // #dr1736-s
 #endif
 }
 
+namespace dr1738 { // dr1738: sup P0136R1
+#if __cplusplus >= 201103L
+struct A {
+  template <typename T>
+  A(int, T) {}
+};
+
+struct B : A {
+  using A::A;
+};
+
+// FIXME: this is well-formed since P0136R1
+template B::B(int, double);
+// since-cxx11-error@-1 {{explicit instantiation of 'B' does not refer to a function template, variable template, member function, member class, or static data member}}
+#endif
+}
+
 // dr1748 is in dr1748.cpp
 
 namespace dr1753 { // dr1753: 11

clang/test/CXX/drs/dr22xx.cpp

@@ -154,6 +154,47 @@ const D &d3(c); // FIXME ill-formed
 #endif
 }
 
+namespace dr2273 { // dr2273: 3.3
+#if __cplusplus >= 201103L
+struct A {
+  A(int = 0) = delete; // #dr2273-A
+};
+
+struct B : A { // #dr2273-B
+  using A::A;
+};
+
+B b;
+// since-cxx11-error@-1 {{call to implicitly-deleted default constructor of 'B'}}
+//   since-cxx11-note@#dr2273-B {{default constructor of 'B' is implicitly deleted because base class 'A' has a deleted default constructor}}
+//   since-cxx11-note@#dr2273-A {{'A' has been explicitly marked deleted here}}
+#endif
+}
+
+namespace dr2277 { // dr2277: partial
+#if __cplusplus >= 201103L
+struct A {
+  A(int, int = 0);
+  void f(int, int = 0); // #dr2277-A-f
+};
+struct B : A {
+  B(int);
+  using A::A;
+
+  void f(int); // #dr2277-B-f
+  using A::f;
+};
+
+void g() {
+  B b{0};
+  b.f(0); // FIXME: this is well-formed for the same reason as initialization of 'b' above
+  // since-cxx11-error@-1 {{call to member function 'f' is ambiguous}}
+  //   since-cxx11-note@#dr2277-A-f {{candidate function}}
+  //   since-cxx11-note@#dr2277-B-f {{candidate function}}
+}
+#endif
+}
+
 namespace dr2292 { // dr2292: 9
 #if __cplusplus >= 201103L
   template<typename T> using id = T;

clang/test/CXX/drs/dr23xx.cpp

@@ -147,6 +147,31 @@ enum struct alignas(64) B {};
 #endif
 } // namespace dr2354
 
+namespace dr2356 { // dr2356: 4
+#if __cplusplus >= 201103L
+struct A {
+  A();
+  A(A &&);                        // #1
+  template<typename T> A(T &&);   // #2
+};
+struct B : A {
+  using A::A;
+  B(const B &);                   // #3
+  B(B &&) = default;              // #4, implicitly deleted
+  // since-cxx11-warning@-1 {{explicitly defaulted move constructor is implicitly deleted}}
+  //   since-cxx11-note@#dr2356-X {{move constructor of 'B' is implicitly deleted because field 'x' has a deleted move constructor}}
+  //   since-cxx11-note@#dr2356-X {{'X' has been explicitly marked deleted here}}
+  //   since-cxx11-note@-4 {{replace 'default' with 'delete'}}
+
+  struct X { X(X &&) = delete; } x; // #dr2356-X
+};
+extern B b1;
+B b2 = static_cast<B&&>(b1);      // calls #3: #1, #2, and #4 are not viable
+struct C { operator B&&(); };
+B b3 = C();                       // calls #3
+#endif
+}
+
 #if __cplusplus >= 201402L
 namespace dr2358 { // dr2358: 16
   void f2() {

clang/test/CXX/drs/dr2504.cpp

@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 -std=c++98 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++11 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK,SINCE-CXX11
+// RUN: %clang_cc1 -std=c++14 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK,SINCE-CXX11
+// RUN: %clang_cc1 -std=c++17 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK,SINCE-CXX11
+// RUN: %clang_cc1 -std=c++20 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK,SINCE-CXX11
+// RUN: %clang_cc1 -std=c++23 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK,SINCE-CXX11
+// RUN: %clang_cc1 -std=c++2c %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK,SINCE-CXX11
+
+namespace dr2504 { // dr2504: no
+#if __cplusplus >= 201103L
+struct V { V() = default; V(int); };
+struct Q { Q(); };
+struct A : virtual V, Q {
+  using V::V;
+  A() = delete;
+};
+int bar() { return 42; }
+struct B : A {
+  B() : A(bar()) {}  // ok
+};
+struct C : B {};
+void foo() { C c; } // bar is not invoked, because the V subobject is not initialized as part of B
+#endif
+}
+
+// FIXME: As specified in the comment above (which comes from an example in the Standard),
+//        we are not supposed to unconditionally call `bar()` and call a constructor
+//        inherited from `V`.
+
+// SINCE-CXX11-LABEL: define linkonce_odr void @dr2504::B::B()
+// SINCE-CXX11-NOT:     br
+// SINCE-CXX11:         call noundef i32 @dr2504::bar()
+// SINCE-CXX11-NOT:     br
+// SINCE-CXX11:         call void @dr2504::A::A(int)
+// SINCE-CXX11-LABEL: }
+
+// CHECK: {{.*}}

clang/test/CXX/drs/dr25xx.cpp

@@ -10,6 +10,8 @@
 // expected-no-diagnostics
 #endif
 
+// dr2504 is in dr2504.cpp
+
 namespace dr2516 { // dr2516: 3.0
                    // NB: reusing 1482 test
 #if __cplusplus >= 201103L

clang/www/cxx_dr_status.html

@@ -6708,7 +6708,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/1150.html">1150</a></td>
     <td>NAD</td>
     <td>Inheriting constructors have not been implemented</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="na" align="center">N/A</td>
   </tr>
   <tr id="1151">
     <td><a href="https://cplusplus.github.io/CWG/issues/1151.html">1151</a></td>
@@ -8730,7 +8730,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/1487.html">1487</a></td>
     <td>CD3</td>
     <td>When are inheriting constructors declared?</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="full" align="center">Clang 3.3</td>
   </tr>
   <tr class="open" id="1488">
     <td><a href="https://cplusplus.github.io/CWG/issues/1488.html">1488</a></td>
@@ -9210,7 +9210,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/1567.html">1567</a></td>
     <td>C++14</td>
     <td>Inheriting constructors and copy/move constructors</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="full" align="center">Clang 3.3</td>
   </tr>
   <tr id="1568">
     <td><a href="https://cplusplus.github.io/CWG/issues/1568.html">1568</a></td>
@@ -10236,7 +10236,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/1738.html">1738</a></td>
     <td>C++14</td>
     <td>Explicit instantiation/specialization of inheriting constructor templates</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="na" align="center">Superseded by <a href="https://wg21.link/P0136R1">P0136R1</a></td>
   </tr>
   <tr id="1739">
     <td><a href="https://cplusplus.github.io/CWG/issues/1739.html">1739</a></td>
@@ -13446,7 +13446,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2273.html">2273</a></td>
     <td>CD5</td>
     <td>Inheriting constructors vs implicit default constructor</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="full" align="center">Clang 3.3</td>
   </tr>
   <tr id="2274">
     <td><a href="https://cplusplus.github.io/CWG/issues/2274.html">2274</a></td>
@@ -13470,7 +13470,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2277.html">2277</a></td>
     <td>CD5</td>
     <td>Ambiguity inheriting constructors with default arguments</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="partial" align="center">Partial</td>
   </tr>
   <tr id="2278">
     <td><a href="https://cplusplus.github.io/CWG/issues/2278.html">2278</a></td>
@@ -13944,7 +13944,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2356.html">2356</a></td>
     <td>CD5</td>
     <td>Base class copy and move constructors should not be inherited</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="full" align="center">Clang 4</td>
   </tr>
   <tr id="2357">
     <td><a href="https://cplusplus.github.io/CWG/issues/2357.html">2357</a></td>
@@ -14832,7 +14832,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2504.html">2504</a></td>
     <td>DR</td>
     <td>Inheriting constructors from virtual base classes</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="none" align="center">No</td>
   </tr>
   <tr class="open" id="2505">
     <td><a href="https://cplusplus.github.io/CWG/issues/2505.html">2505</a></td>