The following program does not compile correctly or type check correctly using the comp compiler and type inference system. However, it is a valid Standard ML program. Modify both the comp compiler and type checker to correctly compile and infer its type. This program is included in the compiler project as test20.sml.

let val [(x, y, z)]= [(1+s+s2 (h) ellop (,)1, true)] in printin x end Output from the type checker should appear as follows. 1 Typechecking is commencing... 2 Here is the AST I 3 letdec (bindval (listpat ([ tuplepat ( [idpat (x),idpat (y), idpat (z)])]), listcon ( [tuple ([str ("hello"), int (1), bool(true) ])])), [apply (id (println), id (x))]) 4 5 6 val [(x, y, z)] : (str * int *bool) list 7 val it unit : 8 The program passed the typechecker.