[clang] [clang][Modules] Complete the implementation of P2615: Meaningful exports (PR #194201)

[Vlad Serebrennikov via cfe-commits]

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+// RUN: %clang_cc1 -std=c++20 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify
+// RUN: %clang_cc1 -std=c++23 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify
+// RUN: %clang_cc1 -std=c++2c -fexceptions -fcxx-exceptions -pedantic-errors %s -verify
+
+export module foo;
+
+namespace cwg2443 { // cwg2443: 23
+
+export template <typename T> class s1 {};
+export template <typename T> class s1<T *> {}; // expected-error {{a specialization cannot be marked 'export'}}
+// expected-note at -1 {{it is exported if the primary template is exported}}
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Endilll wrote:

```suggestion
//   expected-note at -1 {{it is exported if the primary template is exported}}
```

https://github.com/llvm/llvm-project/pull/194201