>          | MatchStar(identifier? target)

+1 on MatchStar(). Much more similiar to the existing node names, and also less semantically-named. 

>           attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

I'm not really sure whether we should continue following this old tradition of int? end_* attributes for new sum types like pattern, considering that it was done for supporting the creation of old nodes 3.8< without any change on 3.8>=. pattern subclasses will only be created on 3.10>= so we should be safe by requiring end_* attributes.