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

[via cfe-commits]

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@@ -7939,7 +7927,14 @@ ExprResult Sema::ActOnStartCXXMemberReference(Scope *S, Expr *Base,
           }
         }
         return ExprError();
+      } else if (Result.isUnset()) {
+        // BuildOverloadedArrowExpr returns an empty expression to indicate
+        // that we need to build a dependent overloaded arrow expression.
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cor3ntin wrote:

I'm not sure RebuildCXXOperatorCallExpr and its caller would deal with an ExprEmpty when calling  
ActOnOverloadedArrowExpr

So yeah, maybe output parameter + assert in treetransform would be better?

https://github.com/llvm/llvm-project/pull/104458