Not to be confused with TCasScriptFunction: TCasScriptFunction is an internal, built-in function or operator. This class represents functions defined by user.
Note that they are also referenced inside function Expression, so you simply change them to set value of this parameter within whole function body.
These are always fresh variables, not referenced anywhere outside of Body. This means that they are owned (always, regardless of OwnedByParentExpression) by this class.