[clang] [clang][c23] Avoid assertion on an invalid static constexpr variable (PR #175927)

[Shafik Yaghmour via cfe-commits]

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@@ -14122,7 +14122,10 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
     // C99 6.7.8p4: All the expressions in an initializer for an object that has
     // static storage duration shall be constant expressions or string literals.
     } else if (VDecl->getStorageClass() == SC_Static) {
-      CheckForConstantInitializer(Init);
+      // Avoid evaluating the initializer twice for constexpr variables. It will
+      // be evaluated later.
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shafik wrote:

Does it make sense to point out where it will be done later? 

https://github.com/llvm/llvm-project/pull/175927