old_contents: 
  "use strict";
  
  function fastNumberParser(args, childValidators, data) {
  
      data = Number(data);
  
      if(isNaN(data)) {
          throw new Error("required Number, got: " + typeof data);
      }
  
      return data;
  
  }
  
  export default {
      name: "FastNumber",
      fn:   fastNumberParser
  };
  
new_contents: 
  "use strict";
  
  function fastNumberParser(args, childValidators, data) {
  
      let d = Number(data);
  
      if(isNaN(d)) {
        throw new Error("required Number, received " + typeof data);
      }
  
      return d;
  
  }
  
  export default {
      name: "FastNumber",
      fn:   fastNumberParser
  };
  
subject: fix fastNumber validator not returning correct type on an error