[clang] [Analysis] Avoid some warnings about exit from noreturn function (PR #144408)

[Serge Pavlov via cfe-commits]

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@@ -399,6 +401,145 @@ static bool isNoexcept(const FunctionDecl *FD) {
   return false;
 }
 
+/// Checks if the given variable, which is assumed to be a function pointer, is
+/// initialized with a function having 'noreturn' attribute.
+static bool isInitializedWithNoReturn(const VarDecl *VD) {
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spavloff wrote:

> We are checking the initializer here, but we don't check to make sure it wasn't assigned since then, right?

No, the statements in a basic block are scanned in backward direction. So if the basic block contains an assignment, it will be tested first. 

> IMO it seems this is a failure of [[noreturn]] not being part of the type :)

You are not alone. For instance, GCC developers have the same opinion: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80495#c1.

https://github.com/llvm/llvm-project/pull/144408