This is due to a missing type annotation for 'ifcase'
in your code:

val ret_fbc =
(
ifcase
| tr=0 =>
  (FBT_CONS(fbc.0) | fbc.1+1, fbc.2)
| tr=1 =>
  (FBT_CONS(fbc.0) | fbc.1, fbc.2+1)
| _ => (FBT_CONS(fbc.0) | fbc.1+1, fbc.2+1)
) : [f1,b1:nat] fb_count(a, f1, b1)

In general, if-exp, case-exp and ifcase-exp should all be given a type
annotation.


On Sat, May 8, 2021 at 9:39 AM d4v3y_5c0n3s <[email protected]> wrote:

>     So, I'm having difficulty understanding a constraint that is failing
> in my code.  The constraint that is failing is "f1 + f1 = 1", which I am
> confused by, because there appears to be no such constraint in my code.
> *Here's what (most of) my code is:*
>         dataprop FBT_IN (int, a:addr) =
>         | FBT_NIL(0, a)
>         | {n:nat} FBT_CONS(n+1, a) of FBT_IN(n, a)
>
>         typedef fb_count (a:addr, f:int, b:int) = [c:nat | f >= 0; b >= 0]
> (FBT_IN(c, a) | int f, int b)
>         typedef f_ind (a:addr, f:int, i:int) = int i
>         typedef b_ind (a:addr, b:int, i:int) = int i
>
>         fn tri_fb_test {c:nat}{l:addr}
>         (
>         pfin: FBT_IN(c, l) | t: ctri, dv: plane
>         ): (FBT_IN(c+1, l) | intBtwe(0,2)) =
>           if ctri_inside_plane(t, dv) then (FBT_CONS(pfin) | 0)
>           else if ctri_outside_plane(t, dv) then (FBT_CONS(pfin) | 1)
>           else (FBT_CONS(pfin) | 2)
>
>         fun loop1 {i,j:nat | i <= j}{a:addr}{f1,b1:nat}
>         ( a: !arrayptr(ctri, a, j), dv: plane,
>         fbc: fb_count(a, f1, b1),
>         j: int j, i: int i ): [f2,b2:nat] fb_count(a, f2, b2) = (
>           if i < j then let
>             val c: ctri = a[i]
>             val (pf_tr | tr) = tri_fb_test(fbc.0 | c, dv)
>             val ret_fbc = ifcase
>               | tr=0 => (FBT_CONS(fbc.0) | fbc.1+1, fbc.2)
>               | tr=1 => (FBT_CONS(fbc.0) | fbc.1, fbc.2+1)
>               | _ => (FBT_CONS(fbc.0) | fbc.1+1, fbc.2+1)
>           in
>             loop1(a, dv, ret_fbc, j, i+1)  // <-- constraint fails on
> this line at "ret_fbc"
>           end else fbc
> *And here's the error produced:*
> $ patscc -tcats cmesh.dats
> /home/tmj90/Goldelish-Engine/source/assets/cmesh.dats: 8604(line=235,
> offs=26) -- 8611(line=235, offs=33): error(3): unsolved constraint:
> C3NSTRprop(C3TKmain(); S2Eeqeq(S2Evar(f1(8784));
> S2Eapp(S2Ecst(add_int_int); S2Evar(f1(8784)), S2Eintinf(1))))
> typechecking has failed: there are some unsolved constraints: please
> inspect the above reported error message(s) for information.
> exit(ATS): uncaught exception:
> _2tmp_2ATS_2dPostiats_2src_2pats_error_2esats__FatalErrorExn(1025)
>
> I suspect the issue is an implicitly generated constraint of some kind,
> but I have no idea where it's coming from.  *However*, I discovered that
> if I comment out these lines:
>             val ret_fbc = ifcase
>               //| tr=0 => (FBT_CONS(fbc.0) | fbc.1+1, fbc.2)
>               //| tr=1 => (FBT_CONS(fbc.0) | fbc.1, fbc.2+1)
>               | _ => (FBT_CONS(fbc.0) | fbc.1+1, fbc.2+1)
> then everything typechecks.  That's the biggest hint I could find, but I
> don't know what going wrong.  Please let me know if you'd like me to
> provide more code, I just didn't want to clutter my initial post.
>
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>

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