Enable the Deprecation Warnings

ALTER SESSION SET PLSQL_WARNINGS='ENABLE:(6019,6020,6021,6022)'

Check warning setting

SELECT DBMS_WARNING.get_warning_setting_string() FROM DUAL

CREATE OR REPLACE PACKAGE pack1 AS 
PRAGMA DEPRECATE(pack1); 
 PROCEDURE foo; 
 PROCEDURE bar; 
 END pack1; 

CREATE OR REPLACE PACKAGE BODY pack1 AS  
 PROCEDURE foo AS  
 BEGIN  
  DBMS_OUTPUT.PUT_LINE('Executing foo.');   
 END foo;  
 PROCEDURE bar IS  
 BEGIN  
  DBMS_OUTPUT.PUT_LINE('bar references foo inside the same package.'); 
  foo;   
 END bar;  
END; 

EXEC pack1.bar

CREATE OR REPLACE PROCEDURE proc2 AS  
BEGIN  
 pack1.foo;  
   
 END proc2;

Display compilation warnings

SELECT * FROM USER_ERRORS