Implement enough of the type checker to get test12.sml to type check correctly. This will mean writing the Wild inference rule as a Prolog predicate, implementing the Match rule’s predicate called typecheckMatch, and the type inference predicate for sequential execution named typecheckSequence as defined in the Sequence rule. The code for test12.sml is given here for reference.

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10 11 12 13 14 15 16 17 18 19 let val zero = 0 fun fib n = let val i = ref zero val current = ref 0 val next ref 1 val tmp = ref 0 in in 20 21 22 23 end while i 10 11 12 13 14 15 16 17 18 19 let val zero = 0 fun fib n = let val i = ref zero val current = ref 0 val next ref 1 val tmp = ref 0 in in 20 21 22 23 end while i