anchor.diff:     ;
   
   value_header
  -   : (KW_CUSTOM)? KW_VALUETYPE ID value_inheritance_spec
  +   : (KW_CUSTOM)? KW_VALUETYPE identifier value_inheritance_spec
      ;
   
   value_inheritance_spec
  
positive.code:    ;
  
  event_abs_decl
     : KW_ABSTRACT KW_EVENTTYPE ID value_inheritance_spec LEFT_BRACE export* RIGHT_BRACE
     ;
  
  event_decl
  
negative.code:    ;
  
  emits_decl
     : KW_EMITS a_scoped_name ID
     ;
  
  publishes_decl
     : KW_PUBLISHES a_scoped_name ID
     ;
  
  consumes_decl
     : KW_CONSUMES a_scoped_name ID
     ;
  
  home_decl
  