Hi Team,
I discovered the strange behavior of the latest version of the SQL Developer 4.2.0.17.089: line numbers in error messages sometimes mismatch with a real line numbers in source code.
For example worksheet:

Compile:

SQL Developer says "Error at line 2".
Check source of procedure:
SELECT LINE, TEXT FROM USER_SOURCE WHERE TYPE='PROCEDURE' AND NAME='TST';

In the source code, the error is in line 3.
Check user_errors:
SELECT ATTRIBUTE, MESSAGE_NUMBER, SEQUENCE, LINE, POSITION, TEXT
FROM USER_ERRORS
WHERE TYPE='PROCEDURE' AND NAME='TST'
ORDER BY SEQUENCE;

Real error line number is 3.
Insert some lines to worksheet:

Result:

Now SQL Developer says "Error at line 6".
SQLDeveloper 4.1.5.21 for this example always output correct line number: 3.
In fact, I compile many source files in the following way:
@c:\somepath\somefilename.pks
@c:\somepath\somefilename.pkb
and I get a similar problem but with even more unpredictable results..
Now I use this workaround: place at the top of each worksheet this lines:
EXECUTE DBMS_OUTPUT.ENABLE(1000000); -- 1-st line may be with any text
CREATE PROCEDURE $$$$$$$$$; /*-- SQL Developer 4.2 workaround*/
/
All lines below this compiles with correct line numbers in error report.
Thank You for your attention.