[Clang][NFC]Use isa instead of dyn_cast in shouldAddReversedEqEq

[liaolucy]

Summary

Fix warning: unused variable ‘MD’

[tbaeder]

This was fixed as https://github.com/llvm/llvm-project/commit/6c49d5db30227d21e929bb12dc046c36ede67fad. Note that for such patches, you don't need to wait for review, like Erich didn't.

[liaolucy]

In D135558#3848649, @tbaeder wrote:

This was fixed as https://github.com/llvm/llvm-project/commit/6c49d5db30227d21e929bb12dc046c36ede67fad. Note that for such patches, you don't need to wait for review, like Erich didn't.

thanks

clang/lib/Sema/SemaOverload.cpp

static bool shouldAddReversedEqEq(Sema &S, SourceLocation OpLoc,
   // finds a function or function template that would correspond
   // ([basic.scope.scope]) to F if its name were operator==, where S is the
   // scope of the class type of o if F is a class member, and the namespace
   // scope of which F is a member otherwise. A function template specialization
   // named operator== is a rewrite target if its function template is a rewrite
   // target.
   DeclarationName NotEqOp = S.Context.DeclarationNames.getCXXOperatorName(
       OverloadedOperatorKind::OO_ExclaimEqual);
-  if (auto *MD = dyn_cast<CXXMethodDecl>(EqFD)) {
+  if (isa<CXXMethodDecl>(EqFD)) {
     // If F is a class member, search scope is class type of first operand.
     QualType RHS = FirstOperand->getType();
     auto *RHSRec = RHS->getAs<RecordType>();
     if (!RHSRec)
       return true;
     LookupResult Members(S, NotEqOp, OpLoc,
                          Sema::LookupNameKind::LookupMemberName);
     S.LookupQualifiedName(Members, RHSRec->getDecl());