test16.txt

*************** Source File ****************

(* 
	This program type checks correctly as it stands, but it should
	not. This is an example of a program that demonstrates that the
	implementation of type checking for MLComp is not sound. 

	This program and why it should not type check correctly is 
	discussed at

	http://www.smlnj.org/doc/Conversion/types.html

	where it explains why this should not pass the type checker
	and how that is handled correctly in SML/NJ. 
*)

let val r = ref(fn x => x)
in
    r := (fn x => x+1);
    !r true
end

******************* AST ********************
letdec(
   bindval(idpat('r'),apply(id('ref'),   func('anon@0',[
      match(idpat('x')      ,id('x')      )
   ]))),
   [
apply(id(':='),tuplecon([id('r')    ,    func('anon@1',[
       match(idpat('x')       ,apply(id('+'),tuplecon([id('x')       ,int('1')]))       )
    ])]))    ,apply(apply(id('!'),id('r')),bool('true'))
   ])
.
************* Type Checking ****************
Typechecking is commencing...
Here is the AST
letdec(bindval(idpat(r),apply(id(ref),func(anon@0,[match(idpat(x),id(x))]))),[apply(id(:=),tuplecon([id(r),func(anon@1,[match(idpat(x),apply(id(+),tuplecon([id(x),int(1)])))])])),apply(apply(id(!),id(r)),bool(true))])


val r : ('a -> 'a) ref


val it : bool

The program passed the typechecker.
********* Target Program Execution *********