anchor.diff:          extendedType?
           satisfiedTypes?
           typeConstraints?
  -        '{' instances? memberOrStatement* '}'
  +        '{' ((instanceStart)=>instances)? memberOrStatement* '}'
       ;
   
   extendedType
  
positive.code:     
  COMPARE
      :   '<=>'
      ;
      
  IN
  
negative.code:     ;
      
  instances
      : instance (',' instance)* (';'|'...')
      ;
  
  instance
      : annotations? 'case' memberName arguments?
      ;
  
  //special rule for syntactic predicate
  instanceStart
      : annotations? 'case'
      ;
  
  typeConstraint
  