[Clang][P1061] Use cast_if_present

Author: ricejasonf

clang/lib/Sema/SemaTemplateVariadic.cpp

@@ -802,8 +802,7 @@ bool Sema::CheckParameterPacksForExpansion(
             CurrentInstantiationScope->findInstantiationOf(ND);
         Decl *B = cast<Decl *>(*Instantiation);
         Expr *BindingExpr = cast<BindingDecl>(B)->getBinding();
-        ResolvedPack =
-            dyn_cast_if_present<ResolvedUnexpandedPackExpr>(BindingExpr);
+        ResolvedPack = cast_if_present<ResolvedUnexpandedPackExpr>(BindingExpr);
         if (!ResolvedPack) {
           ShouldExpand = false;
           continue;