A wrapper that is not is completely defined in its underlying C interface.
Such types must be handled by reference, usually using a pointer. Not
knowing their actual size it cannot be allocated ineither created by an
See also http://en.wikipedia.org/wiki/Opaque_data_type
This exception occurs when Void is passed as the expression
to inspect ("inspect on STRING only).
This exception also occurs when the inspected value selects no branch (when the keyword "else"
not used, one "when" branch _must_ be selected). Some value which is not one of the inspect
constants, if there is no Else_part