# E0263: only one comma is allowed between or after generic parameters

In a TypeScript generic class, function, or type alias, the generic parameter list is a comma-separated list of variables surrounded by `<` and `>`. It is a syntax error for the parameter list to have doubled commas:

    class HashMap<Key, , Hasher> {
      // ...
    }

    function makeHashMap<Key,, Value>(
    ): HashMap<Key, Value, DefaultHasher> {
      return new HashMap(new DefaultHasher());
    }

To fix this error, write a type variable name between the commas:

    class HashMap<Key, Value, Hasher> {
      // ...
    }

Alternatively, remove the extra comma:

    function makeHashMap<Key, Value>(
    ): HashMap<Key, Value, DefaultHasher> {
      return new HashMap(new DefaultHasher());
    }

Introduced in quick-lint-js version 2.8.0.

Documentation for other errors