anchor.diff:  ///     taking a file containing request input and returning a
   ///     <c>Result</c> over <c>Response</c> and <c>Error</c>.
   /// </returns>
  -let runStarling request =
  +let runStarling (request : Request)
  +  : string option -> Result<Response, Error> =
  +
       let config = config()
   
       let opts =
  
positive.code:     | Other of string
  
  /// Prints a top-level program error.
  let printError =
      function
      | Frontend e -> Lang.Frontend.printError e
      | Semantics e -> Semantics.Pretty.printSemanticsError e
  
negative.code:     | HSF
  
  /// Map of -s stage names to Request items.
  let requestMap : Map<string, string * Request> =
      Map.ofList
          [ ("list",
             ("Lists all available phases.",
  