gistfile1.txt

Contract code:
{ parameter
    (or (or (unit %default)
            (pair %getBalance address (or (address %fA12) (pair %fA20 address nat))))
        (or (nat %setTmp) (list %setTmpFromFA20Callback (pair (pair address nat) nat)))) ;
  storage nat ;
  code { SELF %setTmp ;
         SELF %setTmpFromFA20Callback ;
         DIG 2 ;
         UNPAIR ;
         IF_LEFT
           { IF_LEFT
               { DIG 2 ; DIG 3 ; DROP 3 ; NIL operation ; PAIR }
               { SWAP ;
                 DROP ;
                 UNPAIR ;
                 PUSH nat 0 ;
                 NIL operation ;
                 DIG 3 ;
                 IF_LEFT
                   { DIG 4 ;
                     DROP ;
                     PUSH string "FA12 getBalance" ;
                     SWAP ;
                     CONTRACT %getBalance (pair address (contract nat)) ;
                     IF_NONE { PUSH string "None: " ; CONCAT ; FAILWITH } { SWAP ; DROP } ;
                     PUSH mutez 0 ;
                     DIG 5 ;
                     DIG 5 ;
                     PAIR ;
                     TRANSFER_TOKENS }
                   { DIG 5 ;
                     DROP ;
                     UNPAIR ;
                     PUSH string "FA20 balance_of" ;
                     SWAP ;
                     CONTRACT %balance_of
                       (pair (list (pair address nat)) (contract (list (pair (pair address nat) nat)))) ;
                     IF_NONE { PUSH string "None: " ; CONCAT ; FAILWITH } { SWAP ; DROP } ;
                     PUSH mutez 0 ;
                     DIG 6 ;
                     NIL (pair address nat) ;
                     DIG 4 ;
                     DIG 7 ;
                     PAIR ;
                     CONS ;
                     PAIR ;
                     TRANSFER_TOKENS } ;
                 CONS ;
                 PAIR } }
           { SWAP ;
             DIG 2 ;
             DIG 3 ;
             DROP 3 ;
             IF_LEFT
               { NIL operation ; PAIR }
               { IF_CONS
                   { CDR ;
                     SWAP ;
                     IF_CONS
                       { DROP 3 ; PUSH string "FA20 callback argument length != 1" ; FAILWITH }
                       { NIL operation ; PAIR } }
                   { PUSH string "FA20 callback argument length != 1" ; FAILWITH } } } } }

Parameter:
(Left (Right
         (Pair "tz1dkUXrcScDxMTUkNuzTg5iBRHevn7KFBMW"
               (Left "KT1PWx2mnDueood7fEmfbBDKx1D9BAnnXitn"))))
               
Error:
"Either no parameter was supplied to a contract with a non-unit parameter type, a non-unit parameter was passed to an account, or a parameter was supplied of the wrong type",