anchor.diff:     : 'scope'
      ;
   
  +
   SEMPRED
      : 'SEMPRED'
      ;
  
positive.code:    : '/*' .*? '*/' -> skip
     ;
  
  WS
     : (' ' | '\t' | '\r'? '\n') + -> skip
     ;
  
  TOKEN_REF
     : 'A' .. 'Z' ('a' .. 'z' | 'A' .. 'Z' | '_' | '0' .. '9')*
     ;
  
  RULE_REF
     : 'a' .. 'z' ('a' .. 'z' | 'A' .. 'Z' | '_' | '0' .. '9')*
     ;
  
negative.code:    | RULE_REF
     ;
  
  
  CHAR_LITERAL
     : '\'' LITERAL_CHAR '\''
     ;
  