[clang] [Clang] Prevent potential null pointer dereferences (PR #117176)

[Mariya Podchishchaeva via cfe-commits]

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@@ -627,7 +627,7 @@ class Analyzer {
           IsNoexcept = isNoexcept(FD);
         } else if (auto *BD = dyn_cast<BlockDecl>(D)) {
           if (auto *TSI = BD->getSignatureAsWritten()) {
-            auto *FPT = TSI->getType()->getAs<FunctionProtoType>();
+            auto *FPT = TSI->getType()->castAs<FunctionProtoType>();
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Fznamznon wrote:

I'm not sure that if we have a signature, we're guaranteed to have the FunctionProtoType. Perhaps we should leave `getAs` and check that returned value is not null before working with it.
@AaronBallman , any change you can help to clarify that?

https://github.com/llvm/llvm-project/pull/117176