[clang] [StaticAnalyzer][MallocChecker] Detect use-after-free for field address (e.g., &ptr->field) (PR #152462)

[Donát Nagy via cfe-commits]

================
@@ -3156,8 +3156,14 @@ void MallocChecker::checkPreCall(const CallEvent &Call,
   for (unsigned I = 0, E = Call.getNumArgs(); I != E; ++I) {
     SVal ArgSVal = Call.getArgSVal(I);
     if (isa<Loc>(ArgSVal)) {
-      SymbolRef Sym = ArgSVal.getAsSymbol();
-      if (!Sym)
+      const MemRegion *MR = ArgSVal.getAsRegion();
+      if (!MR)
+        continue;
+      const MemRegion *BaseRegion = MR->getBaseRegion();
+      SymbolRef Sym = nullptr;
+      if (const auto *SR = dyn_cast<SymbolicRegion>(BaseRegion))
+        Sym = SR->getSymbol();
----------------
NagyDonat wrote:

```suggestion
      SymbolRef Sym = ArgSVal.getAsSymbol(/*IncludeBaseRegions=*/true);
```
Your code is completely correct and does the right thing, but it can be shortened by using the optional argument of `getAsSymbol` (which will do the same thing).

https://github.com/llvm/llvm-project/pull/152462