[clang] [CIR][NFC] Fix warnings in ClangIR code (PR #133134)

[Morris Hafner via cfe-commits]

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@@ -170,7 +170,7 @@ mlir::Value CIRGenFunction::evaluateExprAsBool(const Expr *e) {
   SourceLocation loc = e->getExprLoc();
 
   assert(!cir::MissingFeatures::pgoUse());
-  if (const MemberPointerType *MPT = e->getType()->getAs<MemberPointerType>()) {
+  if (e->getType()->getAs<MemberPointerType>()) {
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mmha wrote:

I wonder why `getAs` is not `[[nodiscard]]` but hey it's not so no new warning here.

(Maybe `isa` is still better?)

https://github.com/llvm/llvm-project/pull/133134