DATA
  Cmplx
  | Complex
      x : String
      y : Cmplx
      z : Cmplx
  | Simple
      s : String
                
JUDGEMENT
  Gamma, String |- Cmplx : Type, String;

RULE

--------------------------------- [Simple] 
  G, M |- Simple s : a, s

RULE
  G, append M "y" |- b : Ty, Sy;
  G, M |- c : Tz, Sz;
--------------------------------- [Complex]
  G, M |- Complex a b c : arrow Ty Tz, append a (append Sy Sz);