function mergeExpectedParams(signatures, index) {
      var typeNames = uniq(flatMap(signatures, function (signature) {
        return getExpectedTypeNames(signature, index, false);
      }));

      return (typeNames.indexOf('any') !== -1) ? ['any'] : typeNames;
    }
Helper function for creating error messages: create an array with
all available types on a specific argument index.
@param {Signature[]} signatures
@param {number} index
@return {string[]} Returns an array with available types