anchor.diff:    ;
   //[44]
   VarRef
  -  : "$" VarName
  +  : '$' VarName
     ;
   //[45]
   VarName
  
positive.code: 
  // XPath 2.0
  
  //[1]
  XPath
    : Expr
    ;
  //[2]
  Expr
    : ExprSingle ("," ExprSingle)*
    ;
  //[3]
  ExprSingle
  
negative.code:   ;
  //[64]
  ElementTest
    : 'element' '(' (ElementNameOrWildcard (',' TypeName '?'?)?)? ')'
    ;
  //[65]
  ElementNameOrWildcard
    : ElementName | '*'
    ;
  //[66]
  SchemaElementTest
    : 'schema-element' '(' ElementDeclaration ')'
    ;
  //[67]
  ElementDeclaration
  