[clang] [C++26] [Contracts] Support Parser, AST and AST Serialization (1/n) (PR #205739)

[Yihan Wang via cfe-commits]

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@@ -2574,6 +2638,15 @@ class FunctionDecl : public DeclaratorDecl,
 
   void setDeletedAsWritten(bool D = true, StringLiteral *Message = nullptr);
 
+  /// \name C++26 Contracts (P2900R14)
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yronglin wrote:

```suggestion
  /// \name C++26 Contracts.
```

https://github.com/llvm/llvm-project/pull/205739