[clang] [clang][analyzer] Model function addresses in constant initializers (PR #217608)

[Balázs Benics via cfe-commits]

================
@@ -326,6 +326,12 @@ loc::MemRegionVal SValBuilder::getCXXThis(const CXXRecordDecl *D,
 std::optional<SVal> SValBuilder::getConstantVal(const Expr *E) {
   E = E->IgnoreParens();
 
+  if (E->getType()->isFunctionPointerType()) {
+    if (const auto *FD =
+            dyn_cast_or_null<FunctionDecl>(E->getReferencedDeclOfCallee()))
+      return getFunctionPointer(FD);
+  }
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steakhal wrote:

Does this mean that it wouldn't work for references?
```c++
void fa(unsigned) {}

typedef void (&callback)(unsigned);

callback g = fa; // like here?
extern callback h;
```

https://github.com/llvm/llvm-project/pull/217608