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

[via cfe-commits]

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@@ -2484,6 +2498,9 @@ class FunctionDecl : public DeclaratorDecl,
 
   void setDeletedAsWritten(bool D = true) { FunctionDeclBits.IsDeleted = D; }
 
+  /// Only valid if isDeletedAsWritten() returns true.
+  void setDeletedMessage(StringLiteral *Message);
+
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cor3ntin wrote:

I really think this should just be an extra parameter on `setDeletedAsWritten` instead.

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