[clang] [Clang] Fix constant evaluating a captured variable in a lambda (PR #68090)

[Mariya Podchishchaeva via cfe-commits]

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@@ -8367,7 +8367,13 @@ bool LValueExprEvaluator::VisitVarDecl(const Expr *E, const VarDecl *VD) {
 
     if (auto *FD = Info.CurrentCall->LambdaCaptureFields.lookup(VD)) {
       // Start with 'Result' referring to the complete closure object...
-      Result = *Info.CurrentCall->This;
+      if (auto *MD = cast<CXXMethodDecl>(Info.CurrentCall->Callee);
----------------
Fznamznon wrote:

Should it be a `dyn_cast` instead?
```suggestion
      if (auto *MD = dyn_cast<CXXMethodDecl>(Info.CurrentCall->Callee);
```

https://github.com/llvm/llvm-project/pull/68090