## Cmm output should exploit Unf=OtherCon []

It appears to me that generated Cmm does not take into account `Unf= OtherCon []`

, which as far as I know indicates that something is known to be already forced. For example:

```
data S a = S {unS :: !a}
data Tree = Node !Tree !Tree | Leaf !Int
inc :: S Tree -> Tree
inc (S t) = case t of
Leaf n -> Leaf (n + 1)
Node l r -> Node (inc (S l)) (inc (S r))
```

With GHC 8.8.4 and 8.10.2, I get the following worker function:

```
$winc :: Tree -> Tree
$winc
= \ (ww_s1iY
:: Tree
Unf=OtherCon []) ->
case ww_s1iY of {
Node l_a137 r_a138 ->
case $winc l_a137 of dt_X13T { __DEFAULT ->
case $winc r_a138 of dt1_X13V { __DEFAULT ->
Node dt_X13T dt1_X13V
}
};
Leaf dt_d1hC -> Leaf (+# dt_d1hC 1#)
}
```

I expected that `$winc$`

does not check for thunks, but it does:

```
[$winc_entry() // [R2]
...
c1kC:
I64[Sp - 8] = c1kt;
R1 = R2;
Sp = Sp - 8;
if (R1 & 7 != 0) goto c1kt; else goto c1ku;
c1ku:
call (I64[R1])(R1) returns to c1kt, args: 8, res: 8, upd: 8;
c1kt:
```

It's quite common to use records with strict fields, and in all such cases we get worker functions with superfluous forcing like above.