[clang] [docs] Asking to test serialization/deserialization for new C++ feature (PR #200994)

[Chuanqi Xu via cfe-commits]

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@@ -3908,6 +3908,76 @@ directives:
     //   since-cxx17-note@#cwg92-p {{use 'noexcept(false)' instead}}
     // cxx98-14-error@#cwg92-p {{target exception specification is not superset of source}}
 
+
+Testing Modules (Serialization/Deserialization) When implementing a new C++ syntax
+----------------------------------------------------------------------------------
+
+When we implement a new C++ syntax, we need to make sure that it works correctly with modules.
+This means that we need to test that the syntax can be serialized and deserialized (if needed)
+correctly when used in a module. Otherwise, we can't claim the new C++ syntax is supported.
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ChuanqiXu9 wrote:

Done

https://github.com/llvm/llvm-project/pull/200994