SML/NJ Compiler Bug

poly-rec.sml

datatype 'a nested =
    Nest of 'a * 'a list nested
  | Epsilon

fun sumListWith f lst = let
      fun go ([], acc) = acc
        | go (x :: xs, acc) = go (xs, f x + acc)
      in
        go (lst, 0)
      end

fun go (_ : 'a -> int, Epsilon : 'a nested, acc : int) : int = acc
  | go (f, Nest (x, xs), acc) = let
      val go' : ('a list -> int) * 'a list nested * int -> int = Unsafe.cast go
      in
        go' (sumListWith f, xs, f x + acc)
      end

fun sum n = go (fn x => x, n, 0)

val nested : int nested = Nest (1, Nest ([2, 3, 4], Nest ([[5, 6], [7], [8, 9]], Epsilon)))

val nestedSum = sum nested

smlnj-110.79.log

Standard ML of New Jersey v110.79 [built: Sat Oct 26 12:27:04 2019]
- = [autoloading]
[library $SMLNJ-BASIS/basis.cm is stable]
[library $SMLNJ-BASIS/(basis.cm):basis-common.cm is stable]
[autoloading done]
datatype 'a nested = Epsilon | Nest of 'a * 'a list nested
val sumListWith = fn : ('a -> int) -> 'a list -> int
val go = fn : ('a -> int) * 'a nested * int -> int
val sum = fn : int nested -> int
val nested = Nest (1,Nest ([#,#,#],Nest #)) : int nested
val nestedSum = 45 : int

smlnj-110.99.7.1.log

Standard ML of New Jersey [Version 110.99.7.1; 64-bit; January 17, 2025]
- = [autoloading]
[library $SMLNJ-BASIS/basis.cm is stable]
[library $SMLNJ-BASIS/(basis.cm):basis-common.cm is stable]
[autoloading done]
Error: Compiler bug: Contract: UsageMap on v366
****** pass1 ******
 v317(v339[C],v206[FN],v207[PV]) =
    v341(v94[PV],v95[I]) =
       if boxed(v94) [v349] then
          v94.0 -> v67[PV]
          v94.1 -> v68[PV]
          v347(v346[I]) =
             iadd63(v346,v95) -> v86[I]
             v341(v68,v86)
          v206(v347,v67)
       else
          v339(v95)
    v341(v207,(I63t)0)
 v13(v351[C],v305[PR1]) =
    v319(v352[C],v318[FN]) =
       v321(v353[C],v320[PV]) =
          v317(v353,v318,v320)
       v352(v321)
    v351(v319)
 v323(v355[C],v258[PR1]) =
    v258.0 -> v170[I]
    v330(v358[C],v119[FN],v120[PV],v121[I]) =
       if boxed(v120) [v378] then
          v120.0 -> v52[PV]
          v120.1 -> v53[PV]
          v328(v372[C],v329[PV]) =
             v317(v366,v119,v270)
          v376(v374[I]) =
             iadd63(v374,v121) -> v110[I]
             if i63=(v170,(I63t)2) [v365] then
                v279(v366[C],v265[PV]) =
                   v265.0 -> v270[PV]
                   v317(v366,v119,v270)
                v330(v358,v279,v53,v110)
             else
                if i63=(v170,(I63t)3) [v369] then
                   v282(v370[C],v267[PV]) =
                      cast(v328) -> v281[FN]
                      v267.0 -> v273[R64]
                      wrap_f64(v273) -> v275[PV]
                      v267.1 -> v274[R64]
                      wrap_f64(v274) -> v276[PV]
                      v281(v370,v275,v276)
                   v330(v358,v282,v53,v110)
                else
                   cast(v328) -> v283[FN]
                   v330(v358,v283,v53,v110)
          v119(v376,v52)
       else
          v358(v121)
    v355(v330)
 {(I63t)0} -> v286
 v388(v381[FN]) =
    v23(v382[C],v33[PV]) =
       v123(v383[C],v34[I]) =
          v383(v34)
       v381(v382,v123,v33,(I63t)0)
    {(I63t)4,(I63t)0} -> v136
    {(I63t)3,v136} -> v134
    {(I63t)2,v134} -> v132
    {(I63t)6,(I63t)0} -> v145
    {(I63t)5,v145} -> v143
    {(I63t)7,(I63t)0} -> v151
    {(I63t)9,(I63t)0} -> v159
    {(I63t)8,v159} -> v157
    {v157,(I63t)0} -> v155
    {v151,v155} -> v149
    {v143,v149} -> v141
    {v141,(I63t)0} -> v32
    {v132,v32} -> v31
    {(I63t)1,v31} -> v30
    v185(v385[C],v186[I]) =
       v385(v186)
    v387(v386[I]) =
       {v323,v30,v386,v23,v13} -> v169
       v338(v169)
    v381(v387,v185,v30,(I63t)0)
 v323(v388,v286)