(declare-datatypes () ((SystemInt32Array null (SystemInt32Array (pointer Int) (value (Seq Int))))))
(declare-datatypes () ((Fuga null (Fuga (pointer Int) (value Int)))))
(declare-const a SystemInt32Array)
(assert (= a null)) ; ambiguous constant reference,
                    ; more than one constant with the same sort, 
                    ; use a qualified expression (as <symbol> <sort>) to disumbiguate null
(check-sat)