LetExp([
 TypeDec[
  (a,
   ArrayTy(int)),
  (b,
   NameTy(a))],
 VarDec(arr1,true,SOME(a),
  ArrayExp(b,
   IntExp(10),
   IntExp(0)))],
 VarExp(
  SubscriptVar(
   SimpleVar(arr1),
   IntExp(2))))