[clang] Reapply "[Clang][Sema] Use the correct lookup context when building overloaded 'operator->' in the current instantiation (#104458)" (PR #109422)

[Erich Keane via cfe-commits]

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@@ -8002,15 +7991,26 @@ ExprResult Sema::ActOnStartCXXMemberReference(Scope *S, Expr *Base,
         return ExprError();
       }
 
+      bool IsDependent;
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erichkeane wrote:

Please initialize this to false anyway.

https://github.com/llvm/llvm-project/pull/109422