anchor.diff:     ;
   
   IDENTIFIER
  -   : [a-zA-Z] [a-zA-Z0-9]+
  -   ;
  -
  -DIGIT
  +   : [a-zA-Z] [a-zA-Z0-9]*
  +   ;
  +
  +fragment DIGIT
      : [0-9]
      ;
   
  
positive.code:    | tagcase_stmt
     | tagtest_stmt
     | tagwait_stmt
     | 'abort' 'return' (expression (',' expression)*)?
     | 'yield' (expression (',' expression)*)*
     | 'abort'? 'signal' name (expression (',' expression)*)?
     | 'abort'? 'exit' name (expression (',' expression)*)?
     | 'abort'? 'break'
  
negative.code:    ;
  
  for_stmt
     : 'for' decl (',' decl)* 'in' call 'do' body 'end'
     | 'for' idn (',' idn)* 'in' call 'do' body 'end'
     ;
  
  if_stmt
  