Crystal's StringScanner does not support every method which Ruby's StringScanner does.

• #beginning_of_line?
• #get_byte
• #getch
• #match
• #match?
• #matched?
• #matched_size
• #exist?
• #pos
• #rest?
• #rest_size
• #pre_match
• #post_match
• #<<
• #concat
• #unscan