anchor.diff:     | select_with_parens indirection? # c_expr_expr
      | explicit_row # c_expr_expr
      | implicit_row # c_expr_expr
  +   | row OVERLAPS row /* 14*/
  +
  +   # c_expr_expr
      ;
   
   plsqlvariablename
  
positive.code:    | OPTION
     | PERFORM
     //| PG_CONTEXT
     //| PG_DATATYPE_NAME
     //| PG_EXCEPTION_CONTEXT
     //| PG_EXCEPTION_DETAIL
     //| PG_EXCEPTION_HINT
     | PRINT_STRICT_PARAMS
     | PRIOR
  
negative.code:    ;
  
  generic_set
     : var_name (TO | EQUAL) var_list
     ;
  
  set_rest_more
  