anchor.diff:  
   // --------------------
   // Inverted element set
  -
   notSet
      : NOT setElement
      | NOT blockSet
  
positive.code: grammarType
     : (LEXER GRAMMAR | PARSER GRAMMAR | GRAMMAR)
     ;
  
  // This is the list of all constructs that can be declared before
  // the set of rules that compose the grammar, and is invoked 0..n
  // times by the grammarPrequel rule.
  
  prequelConstruct
     : optionsSpec
  
negative.code: 
  // --------------
  // Exception spec
  throwsSpec
     : THROWS identifier (COMMA identifier)*
     ;
  