anchor.diff:  importVariables: FOR_T importVariable (COMMA importVariable);
   
   // call
  -call: callHead (DOT call)*;
  -callBlock: id block;
  -callSignature: id LPAREN enumeration? RPAREN;
  -callHead
  -    : callSignature
  -    | callBlock
  -    | id
  -    ;
  +call: id (callInvoke | block)? (DOT call)*;
  +callInvoke:(LPAREN enumeration? RPAREN) ;
  +
   // expressions
   expression
       : expression compoundExpression
       | BANG expression
  -    | LPAREN expression  RPAREN
  +    | LPAREN expression RPAREN
       | atomExpression
       ;
   
  
positive.code:      ;
  
  atomExpression
      : id
      | boolE
      | charE
      | stringE
      | numE
  
negative.code:     | GE
      | NOTEQUAL
      | IS
      ;
  classOpGetter: operatorGetter block?;
  classOpSetter: operatorSetter oneArgument block;
  oneArgument: LPAREN id RPAREN;
  subscript: LBRACK enumeration RBRACK;
  classSubscriptGet:  subscript block;
  classSubscriptSet:  subscript ASSIGN oneArgument block;
  classSetter: id assignmentSetter block;
  assignmentSetter:ASSIGN oneArgument;
  arguments: LPAREN (id (COMMA id)*)? RPAREN;
  