Cast Documented Behaviour?

Question

Take a look at the following sample. In the last statement, I use a CAST and understand why it only shows the first letter. But why does it do the same for the other column in which I don't use the CAST?
SQL> select *
  2    from v$version
  3  /
BANNER
Personal Oracle Database 10g Release 10.2.0.1.0 - Production
PL/SQL Release 10.2.0.1.0 - Production
CORE    10.2.0.1.0      Production
TNS for 32-bit Windows: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production
SQL>
SQL> drop table t purge
  2  /
Table dropped.
SQL>
SQL> create table t
  2  as
  3  select object_name
  4    from all_objects
  5   where rownum <= 5
  6  /
Table created.
SQL> select object_name
  2    from t
  3  /
OBJECT_NAME
ICOL$
I_USER1
CON$
UNDO$
C_COBJ#
SQL>
SQL> select object_name
  2       , cast (object_name as varchar2(1))
  3    from t
  4  /
OBJECT_NAME                    C
I                              I
I                              I
C                              C
U                              U
C                              C
SQL>
SQL> Is this documented behaviour? I couldn't find anything using Tahiti.oracle.com or the forums...

Answer 1

It's trying to cast to x%type, which is DATE. But even if you replace it with DATE you get the same error.
  1  DECLARE
  2     i   DATE;
  3     x   DATE;
  4  BEGIN
  5     i := CAST (SYSDATE AS date);
  6* END;
cmsgpro_user@XOPDEV> /
   i := CAST (SYSDATE AS date);
ERROR at line 5:
ORA-06550: line 5, column 15:
PLS-00382: expression is of wrong type
ORA-06550: line 5, column 4:
PL/SQL: Statement ignored
cmsgpro_user@XOPDEV> ED
Wrote file afiedt.buf
  1  DECLARE
  2     i   DATE;
  3     x   DATE;
  4  BEGIN
  5     i := CAST (SYSDATE AS VARCHAR2);
  6* END;
cmsgpro_user@XOPDEV> /
PL/SQL procedure successfully completed.