namespace {
// Eliminate values that pass through the CaseRegionOp or IfRegionOp branches.
template <class CaseOrIfRegionOp>
class CaseOrIfRegionEliminatePassThrough
    : public OpRewritePattern<CaseOrIfRegionOp> {
  using OpRewritePattern<CaseOrIfRegionOp>::OpRewritePattern;

  LogicalResult matchAndRewrite(CaseOrIfRegionOp op,
                                PatternRewriter& rewriter) const override {