[Clang][Sema] Fix crash with const qualified member operator new

We should diagnose a const qualified member operator new but we fail to do so
and this leads to crash during debug info generation.

The fix is to diagnose this as ill-formed in the front-end.

Fixes: llvm#79748

clang/docs/ReleaseNotes.rst

@@ -188,6 +188,8 @@ Bug Fixes to C++ Support
   and (`#79745 <https://github.com/llvm/llvm-project/issues/79745>`_)
 - Fix incorrect code generation caused by the object argument of ``static operator()`` and ``static operator[]`` calls not being evaluated.
   Fixes (`#67976 <https://github.com/llvm/llvm-project/issues/67976>`_)
+- Fix crash and diagnostic with const qualified member operator new.
+  Fixes (`#79748 <https://github.com/llvm/llvm-project/issues/79748>`_)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Sema/SemaType.cpp

@@ -5907,15 +5907,24 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
     //  - the type-id in the default argument of a type-parameter, or
     //  - the type-id of a template-argument for a type-parameter
     //
+    // C++23 [dcl.fct]p6 (P0847R7)
+    // ... A member-declarator with an explicit-object-parameter-declaration
+    // shall not include a ref-qualifier or a cv-qualifier-seq and shall not be
+    // declared static or virtual ...
+    //
     // FIXME: Checking this here is insufficient. We accept-invalid on:
     //
     //   template<typename T> struct S { void f(T); };
     //   S<int() const> s;
     //
     // ... for instance.
     if (IsQualifiedFunction &&
-        !(Kind == Member && !D.isExplicitObjectMemberFunction() &&
-          D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_static) &&
+        // Check for non-static member function and not and
+        // explicit-object-parameter-declaration
+        (Kind != Member || D.isExplicitObjectMemberFunction() ||
+         D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static ||
+         (D.getContext() == clang::DeclaratorContext::Member &&
+          D.isStaticMember())) &&
         !IsTypedefName && D.getContext() != DeclaratorContext::TemplateArg &&
         D.getContext() != DeclaratorContext::TemplateTypeArg) {
       SourceLocation Loc = D.getBeginLoc();

clang/test/SemaCXX/function-type-qual.cpp

@@ -37,3 +37,21 @@ void instantiateArrayDecay() {
   int a[1];
   arrayDecay(a);
 }
+
+namespace GH79748 {
+typedef decltype(sizeof(0)) size_t;
+struct A {
+  void* operator new(size_t bytes) const; //expected-error {{static member function cannot have 'const' qualifier}}
+  void* operator new[](size_t bytes) const; //expected-error {{static member function cannot have 'const' qualifier}}
+
+  void operator delete(void*) const; //expected-error {{static member function cannot have 'const' qualifier}}
+  void operator delete[](void*) const; //expected-error {{static member function cannot have 'const' qualifier}}
+};
+struct B {
+  void* operator new(size_t bytes) volatile; //expected-error {{static member function cannot have 'volatile' qualifier}}
+  void* operator new[](size_t bytes) volatile; //expected-error {{static member function cannot have 'volatile' qualifier}}
+
+  void operator delete(void*) volatile; //expected-error {{static member function cannot have 'volatile' qualifier}}
+  void operator delete[](void*) volatile; //expected-error {{static member function cannot have 'volatile' qualifier}}
+};
+}