checkFiltersDisjointStatements: check for actual filters

The children of a sequence node should be proper filters
(not mapping filters).

Author: Sven Verdoolaege

tc/core/polyhedral/scop.cc

@@ -141,7 +141,7 @@ void checkFiltersDisjointStatements(const ScheduleTree* root) {
        ScheduleTree::collect(root, detail::ScheduleTreeType::Sequence)) {
     isl::union_set alreadyVisitedStmts;
     for (auto child : node->children()) {
-      auto filterNode = child->elemAsBase<ScheduleTreeElemFilter>();
+      auto filterNode = child->elemAs<ScheduleTreeElemFilter>();
       TC_CHECK(filterNode) << "expected children of sequence to be filters";
       auto filter = filterNode->filter_.universe();
       if (!alreadyVisitedStmts.get()) {