// The NextIteration.Source operation returns an extra token consumed by the sink.
    TfeTokenType:$token,
    TfeControlType:$control
  );

  let builders = [
    OpBuilder<(ins "Type":$result_type,
      CArg<"ArrayRef<NamedAttribute>", "{}">:$attributes),
    [{
      Type token_type = TokenType::get($_builder.getContext());
      Type control_type = ControlType::get($_builder.getContext());

  let regions = (region VariadicRegion<AnyRegion>:$body);

  let skipDefaultBuilders = 1;

  let builders = [
    OpBuilder<(ins "StringRef":$name, "FunctionType":$type,
      CArg<"ArrayRef<NamedAttribute>", "{}">:$attrs)>
  ];

  let extraClassDeclaration = [{
    LogicalResult verifyType() { return success(); }

    mlir::Region *getCallableRegion();