This operation is not defined for system tables.
unsuccessful metadata update.
RECREATE PACKAGE BODY IBE$DBG$PKG$1 failed.
Default values for parameters are allowed only in declaration of packaged function IBE$DBG$PKG$1.TEST$FUNC.
-----------------------------------------------------------------------------------------------------------
SQLCODE: -607
SQLSTATE: 42000
GDSCODE: 335544351

set term ! ;
create or alter procedure test$proc
as
declare function test$func(lParam1 integer = 0) --если убрать дефолтное значение - ошибки нет
        returns integer
        as
        begin
          return 0;
        end
--declare procedure test$proc$in(lParam1 integer = 0) --тут тоже самое
--        as
--        begin
--        end
begin
  suspend;
end!
set term ; !

Invalid token.
Dynamic SQL Error.
SQL error code = -104.
Token unknown - line 11, column 1.
END.
----------------------------------
SQLCODE: -104
SQLSTATE: 42000
GDSCODE: 335544569

set term ! ;
create or alter procedure test$proc
as
declare function test$func(lParam1 integer = 0) --Работает
        returns integer
        as
        begin
          return 0;
        end
declare procedure test$proc$out(lParam1 integer = 0) --Работает
        returns (ret1 integer)
        as
        begin
          suspend;
        end
declare procedure test$proc$in(lParam1 integer = 0) --Ошибка
        as
        begin
        end
begin
  suspend;
end!
set term ; !