[clang] [Clang] [C++26] Implement P2573R2: `= delete("should have a reason");` (PR #86526)

[Erich Keane via cfe-commits]

================
@@ -3092,30 +3092,65 @@ bool FunctionDecl::isVariadic() const {
   return false;
 }
 
-FunctionDecl::DefaultedFunctionInfo *
-FunctionDecl::DefaultedFunctionInfo::Create(ASTContext &Context,
-                                            ArrayRef<DeclAccessPair> Lookups) {
-  DefaultedFunctionInfo *Info = new (Context.Allocate(
-      totalSizeToAlloc<DeclAccessPair>(Lookups.size()),
-      std::max(alignof(DefaultedFunctionInfo), alignof(DeclAccessPair))))
-      DefaultedFunctionInfo;
+FunctionDecl::DefaultedOrDeletedFunctionInfo *
+FunctionDecl::DefaultedOrDeletedFunctionInfo::Create(
+    ASTContext &Context, ArrayRef<DeclAccessPair> Lookups,
+    StringLiteral *DeletedMessage) {
+  static constexpr size_t Alignment =
+      std::max({alignof(DefaultedOrDeletedFunctionInfo),
+                alignof(DeclAccessPair), alignof(StringLiteral *)});
+  size_t Size = totalSizeToAlloc<DeclAccessPair, StringLiteral *>(
+      Lookups.size(), !!DeletedMessage);
+
+  DefaultedOrDeletedFunctionInfo *Info =
+      new (Context.Allocate(Size, Alignment)) DefaultedOrDeletedFunctionInfo;
   Info->NumLookups = Lookups.size();
+  Info->HasDeletedMessage = !!DeletedMessage;
----------------
erichkeane wrote:

```suggestion
  Info->HasDeletedMessage = DeletedMessage != nullptr;
```

https://github.com/llvm/llvm-project/pull/86526