Page.re

module Page = {
  type action =
    | NoOp;
  type ledger = {
    id: string,
    statementId: string,
    actor: string,
    influencer: string,
    referenceType: string,
    paymentId: string,
    amount: string,
    timestamp: int
  };
  type state = { items: list(ledger) };
  let component = ReasonReact.reducerComponent("PageSearch");
  let make = _children => {
    ...component,
    initialState: () => { items: [] },
    reducer: (action, _state: state) =>
      switch (action) {
      | NoOp => ReasonReact.NoUpdate
      },
    render: _self =>
      <div>
        <div className="search-bar-container">
          <table className="ledger"> <TableHeader /> </table>
        </div>
      </div>
  };
};

let render = root => ReactDOMRe.render(<Page />, root);

Thanks to the very helpful hello123#8705 on the ReasonML discord channel, I learned that you have to annotate the state variable so that the program will compile.