[clang] [clang] Implement CWG3135 - constexpr structured bindings with prvalues from tuples (PR #191880)

[Yanzuo Liu via cfe-commits]

================
@@ -1,16 +1,61 @@
-// RUN: %clang_cc1 -std=c++98 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected
-// RUN: %clang_cc1 -std=c++11 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected
-// RUN: %clang_cc1 -std=c++14 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected
-// RUN: %clang_cc1 -std=c++17 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected
-// RUN: %clang_cc1 -std=c++20 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected
-// RUN: %clang_cc1 -std=c++23 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected
-// RUN: %clang_cc1 -std=c++2c -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected
+// RUN: %clang_cc1 -std=c++98 %s -fexceptions -fcxx-exceptions -pedantic-errors -verify-directives -verify=expected,cxx98-14
+// RUN: %clang_cc1 -std=c++11 %s -fexceptions -fcxx-exceptions -pedantic-errors -verify-directives -verify=expected,cxx98-14,cxx11-17,since-cxx11
+// RUN: %clang_cc1 -std=c++14 %s -fexceptions -fcxx-exceptions -pedantic-errors -verify-directives -verify=expected,cxx98-14,cxx14-17,cxx11-17,since-cxx11,since-cxx14
+// RUN: %clang_cc1 -std=c++17 %s -fexceptions -fcxx-exceptions -pedantic-errors -verify-directives -verify=expected,cxx14-17,cxx11-17,since-cxx11,since-cxx14,since-cxx17
+// RUN: %clang_cc1 -std=c++20 %s -fexceptions -fcxx-exceptions -pedantic-errors -verify-directives -verify=expected,since-cxx11,since-cxx14,since-cxx17,since-cxx20
+// RUN: %clang_cc1 -std=c++23 %s -fexceptions -fcxx-exceptions -pedantic-errors -verify-directives -verify=expected,since-cxx11,since-cxx14,since-cxx17,since-cxx20
+// RUN: %clang_cc1 -std=c++2c %s -fexceptions -fcxx-exceptions -pedantic-errors -verify-directives -verify=expected,since-cxx11,since-cxx14,since-cxx17,since-cxx20
 
+// RUN: %clang_cc1 -std=c++98 %s -fexceptions -fcxx-exceptions -pedantic-errors -fexperimental-new-constant-interpreter -verify-directives -verify=expected,cxx98-14
+// RUN: %clang_cc1 -std=c++11 %s -fexceptions -fcxx-exceptions -pedantic-errors -fexperimental-new-constant-interpreter -verify-directives -verify=expected,cxx98-14,cxx11-17,since-cxx11
+// RUN: %clang_cc1 -std=c++14 %s -fexceptions -fcxx-exceptions -pedantic-errors -fexperimental-new-constant-interpreter -verify-directives -verify=expected,cxx98-14,cxx14-17,cxx11-17,since-cxx11,since-cxx14
+// RUN: %clang_cc1 -std=c++17 %s -fexceptions -fcxx-exceptions -pedantic-errors -fexperimental-new-constant-interpreter -verify-directives -verify=expected,cxx14-17,cxx11-17,since-cxx11,since-cxx14,since-cxx17
+// RUN: %clang_cc1 -std=c++20 %s -fexceptions -fcxx-exceptions -pedantic-errors -fexperimental-new-constant-interpreter -verify-directives -verify=expected,since-cxx11,since-cxx14,since-cxx17,since-cxx20
+// RUN: %clang_cc1 -std=c++23 %s -fexceptions -fcxx-exceptions -pedantic-errors -fexperimental-new-constant-interpreter -verify-directives -verify=expected,since-cxx11,since-cxx14,since-cxx17,since-cxx20
+// RUN: %clang_cc1 -std=c++2c %s -fexceptions -fcxx-exceptions -pedantic-errors -fexperimental-new-constant-interpreter -verify-directives -verify=expected,since-cxx11,since-cxx14,since-cxx17,since-cxx20
 
-// expected-no-diagnostics
+// cxx98-14-no-diagnostics
 
 namespace cwg3106 { // cwg3106: 2.7
 #if __cplusplus >= 201103L
 const char str[9] = R"(\u{1234})";
 #endif
 } // namespace cwg3106
+
+namespace cwg3135 { // cwg3135: 23
+#if __cplusplus >= 201703L
+struct Pinned {
+  Pinned(const Pinned&) = delete; // #cwg3135-pinned-ctor
+  Pinned& operator=(const Pinned&) = delete;
+};
+
+struct Source {
+  operator Pinned&&() const;
+  
+  template<int>
+  Source get() noexcept;
+};
+} // namespace cwg3135
+
+namespace std {
+  template<typename> struct tuple_size;
+  template<int, typename> struct tuple_element;
+
+  template<>
+  struct tuple_size<cwg3135::Source> {
+    static constexpr int value = 1;
+  };
+  
+  template<>
+  struct tuple_element<0, cwg3135::Source> { using type = cwg3135::Pinned; };
+} // namespace std
+
+namespace cwg3135 {
+// CWG3135: `x` is of type Pinned rather than Pinned&&. 
+// This leads to the deleted copy ctor being called.
+auto [x] = Source{};
+// since-cxx17-error-re at -1 {{call to deleted constructor of 'std::tuple_element<0U{{L*}}, Source>::type' (aka 'cwg3135::Pinned')}}
+// since-cxx17-note at -2 {{in implicit initialization of binding declaration 'x'}}
+// since-cxx17-note@#cwg3135-pinned-ctor {{'Pinned' has been explicitly marked deleted here}}
----------------
zwuis wrote:

```suggestion
//   since-cxx17-note at -2 {{in implicit initialization of binding declaration 'x'}}
//   since-cxx17-note@#cwg3135-pinned-ctor {{'Pinned' has been explicitly marked deleted here}}
```

https://clang.llvm.org/docs/InternalsManual.html#c-defect-report-tests

https://github.com/llvm/llvm-project/pull/191880