[clang] [LifetimeSafety] Detect use-after-scope through fields in member calls (PR #191731)

[via cfe-commits]

================
@@ -723,6 +723,17 @@ void FactsGenerator::handleInvalidatingCall(const Expr *Call,
         ThisList->getOuterOriginID(), Call));
 }
 
+void FactsGenerator::handleImplicitObjectFieldUses(const Expr *Call,
+                                                   const FunctionDecl *FD) {
+  const auto *MD = dyn_cast<CXXMethodDecl>(FD);
+  if (!MD || !MD->isInstance())
+    return;
+
+  for (const auto *Field : MD->getParent()->fields())
----------------
NeKon69 wrote:

I tried implementing this, but unfortunately, even though fields from base class do run `UseFields` function, and each get a `UseFact`, they don't produce a warning? I suspect that may be because they are getting associated with the wrong thing here, I am not entirely sure to be honest.

So this still doesn't get diagnosed currently:

```
struct X {
    int* x;
};

struct Y : X {
    int* y;
    int foo();
    void bar() {
        {
            int a;
            x = &a;
        }
        foo();
        x = nullptr;
    }
};
```

https://github.com/llvm/llvm-project/pull/191731