[MLton] building mlton on Snow Leopard

[John Reppy]

I'm trying to compile mlton (revision 7228) using the command

	make TARGET_ARCH=x86_64 smlnj-mlton

on Snow Leopard, but I'm hitting type errors in ssa/combine- 
conversions.fun

ssa/combine-conversions.fun:57.5-58.60 Warning: type vars not  
generalized because of
    value restriction are instantiated to dummy types (X1,X2,...)
ssa/combine-conversions.fun:64.21-64.46 Error: operator and operand  
don't agree [tycon mismatch]
   operator domain: ?.S.t * ?.X1 option
   operand:         ?.S.t * (('Z * 'Y * {signed:'X}) * 'W) option
   in expression:
     set (x3,SOME conversion)
ssa/combine-conversions.fun:68.7-76.20 Error: case object and rules  
don't agree [tycon mismatch]
   rule domain: ((?.S.t * 'Z * {signed:bool}) * 'Y) option
   object: ?.X1 option
   in expression:
     (case (get x2)
       of NONE => stop ()
        | SOME (prev  as (<pat>,<pat>)) =>
            if (<exp> <= <exp>) andalso (<exp> <= <exp>)
            then loop prev
            else if <exp> andalso <exp>
                 then loop <exp>
                 else if <exp> then <exp> else <exp>)
ssa/combine-conversions.fun:93.10-100.21 Error: case object and rules  
don't agree [tycon mismatch]
   rule domain: ((?.S.t * ?.S.t * {signed:bool}) * ?.S.t) option option
   object: ?.X1 option Option.t
   in expression:
     (case (Option.map (var,get))
       of SOME (SOME (<pat>,<pat>)) =>
            if WordSize.equals (<exp>,<exp>)
            then Var x2
            else PrimApp
                   {args=Vector.new1 <exp>,prim=Prim.wordExtdToWord  
<exp>,
                    targs=Vector.new0 <exp>}
        | _ => exp)