anchor.diff:    ;
   
   assignment
  -  : <assoc=right> qualifiedName '=' expression
  +  : <assoc=right> identifier '=' expression
     ;
   
   forLoop
  -  : FOR '(' Identifier ':' expression ')' block
  +  : FOR '(' identifier ':' expression ')' block
     ;
   
   returnStatement
     : RETURN expression;
  +
  +identifier
  +  : Identifier
  +  ;
   
   typeName
     : STRING
  
positive.code:   ;
  
  formalParameter
    : typeName Identifier
    ;
  
  block
  
negative.code:   ;
  
  expression
    : identifier
    | literal
    | functionCall
    | assignment
    ;
  
  literal
  