function getLowestConversionIndex (param) {
      var min = 999;

      for (var i = 0; i < param.types.length; i++) {
        if (!isExactType(param.types[i])) {
          min = Math.min(min, param.types[i].conversionIndex);
        }
      }

      return min;
    }
Find the lowest index of the conversion of all types of the parameter
having a conversion
@param {Param} param
@return {number} Returns the lowest index of the conversions of this type