parser.emitError(parser.getNameLoc(), "unknown type: ") << keyword;
  return Type();
}

/// Print a type registered to this dialect.
void FallbackDialect::printType(Type type, DialectAsmPrinter &os) const {
  if (mlir::isa<TFTensorType>(type)) {
    os << "tf_tensor";
    return;
  }

  if (mlir::isa<TFAllocatorType>(type)) {
    os << "tf_allocator";
    return;
  }

  return mlir::Type();
}

// Print a type registered to this dialect.
void TensorflowMlrtDialect::printType(mlir::Type type,
                                      mlir::DialectAsmPrinter &os) const {
  if (mlir::isa<TFTensorType>(type)) {
    os << "tensor";
    return;
  }

  llvm_unreachable("unexpected tf_mlrt type kind");
}

}  // namespace tf_mlrt
}  // namespace tensorflow

  return mlir::Type();
}

// Print a type registered to this dialect.
void MlrtDialect::printType(mlir::Type type,
                            mlir::DialectAsmPrinter &os) const {
  if (mlir::isa<FutureType>(type)) {
    os << "future";
    return;
  }

  if (mlir::isa<PromiseType>(type)) {
    os << "promise";
    return;
  }

  parser.emitError(parser.getNameLoc())
      << "unknown tf_executor type: " << data_type;
  return nullptr;
}

void TensorFlowExecutorDialect::printType(Type type,
                                          DialectAsmPrinter &os) const {
  if (mlir::isa<ControlType>(type)) {
    os << "control";
    return;
  }
  if (mlir::isa<TokenType>(type)) {
    os << "token";
    return;
  }

  // more efficient computationally.
  bool shouldMaterializeInto(Region* region) const final {
    return isa<WhileOp>(region->getParentOp());
  }
};

void TFLDialect::printType(Type type, DialectAsmPrinter& os) const {
  if (type.isa<ControlType>()) {
    os << "control";
    return;
  }
  os << "<unknown TFL type>";
}

Type TFLDialect::parseType(DialectAsmParser& parser) const {