XML SQL functions causing internal errors in PL/SQL

Question

Still busy searching through Metalink, but have yet to find anything useful. Maybe someone can point me towards a URL or a doc ref that has some hints on how to solve the following:
Oracle: 10.2.0.1.0 46bit
O/S: HP-UX 11
SQL> var l varchar2(4000)
SQL>
SQL>
SQL> select XMLForest( 123 as "ID" ) as L from dual;
L
<ID>123</ID>
SQL> begin
  2     select XMLForest( 123 as "ID" ) into :l from dual;
  3  end;
  4  /
        select XMLForest( 123 as "ID" ) into :l from dual;
ERROR at line 2:
ORA-06550: line 2, column 2:
PLS-00801: internal error [*** ASSERT at file pdw4.c, line  793;
Cannot coerce between type 43 and type 30; anon_c000000044b37bb0__AB[2, 2]]
SQL> begin
  2     EXECUTE IMMEDIATE 'select XMLForest( 123 as "ID" ) from dual' into :l;
  3* end;
SQL> /
PL/SQL procedure successfully completed.
SQL> print l
L
<ID>123</ID>

Answer 1

Ah.. found the problem. The function returns a type which result is implicitly type casted to a varchar2 it seems when running a SELECT on it via the SQL engine.
PL/SQL sees it as a type (which it is) and expects you to put it into a var of the same type. It does not allow/perform the implicit conversion to varchar2.
But then SQL is not Turing Complete so I guess we'll have to let the SQL Engine slide on doing these implicit conversions... :-)