[clang] Sema: detect adjusted function prototypes to fix crash with __typeof + __asm + noreturn (#173598) (PR #174092)

[via cfe-commits]

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@@ -9529,12 +9529,23 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     //     declarator to still have a function type. e.g.,
     //       typedef void func(int a);
     //       __attribute__((noreturn)) func other_func; // This has a prototype
+    auto HasFunctionPrototype = [&](QualType T) -> bool {
+      if (T.isNull())
+        return false;
+      if (T->getAs<FunctionProtoType>())
+        return true;
+      if (const FunctionType *Adjusted = T->getAsAdjusted<FunctionType>())
+        return isa<FunctionProtoType>(Adjusted);
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Sirraide wrote:

Does this actually do anything here? As I understand it, `getAs()` should already ignore all type sugar

https://github.com/llvm/llvm-project/pull/174092