Cause: The construct or expression does
not designate a value that can be assigned to a variable. For example, the
datatype name NUMBER cannot appear on the right hand side of an assignment
statement as in X := NUMBER.
Action: Correct the illegal assignment
statement.

Relared Errors:
PLS-00309: with
%%LAST attribute, `string` must be a variable of an enumerated
type
PLS-00310: with
%%ROWTYPE attribute, `string` must name a table, cursor or
cursor-var
PLS-00311: the
declaration of string is incomplete or malformed
PLS-00312: a
positional parameter association may not follow a named
association
PLS-00313:
`string` not declared in this scope
PLS-00314:
TABLE declarations are not allowed as PL/SQL local variables
PLS-00315:
Implementation restriction: unsupported table index type
PLS-00316:
PL/SQL TABLEs must use a single index
PLS-00317:
incomplete type string was not completed in its declarative
region
PLS-00318: type
string is malformed because it is a non-REF mutually recursive
type