anchor.diff:                 ^(FIELDDEF DOC TYPENAME[$t, "Int64"] VARIABLENAME[$t, "user1"])
                  ^(FIELDDEF DOC TYPENAME[$t, "Int64"] VARIABLENAME[$t, "user2"])
              )
  -           declarations
  +           declarations?
       ;
   
   // extra attributes that we throw away
  
positive.code:     ;
  
  declarations
      :   (versiondefine | basicdefine | enumdefine | structdefine | bitflagsdefine)*
      ;
  
  versiondefine
  
negative.code:         (HEADER_XML SHORTDOC*)? // not really required, but usually present
          (HEADER_DOCTYPE SHORTDOC*)? // not really required, but usually present
          t=TAG_START_ROOT anyattribute* TAG_CLOSE SHORTDOC*
          declarations?
          TAG_END_ROOT SHORTDOC*
          EOF
          -> 
  