unison/unison-src/transcripts/fix2712.md

``` ucm :hide
scratch/main> builtins.merge
```

``` unison
unique type Map k v = Tip | Bin Nat k v (Map k v) (Map k v)

mapWithKey : (k ->{e} a ->{e} b) -> Map k a ->{e} Map k b
mapWithKey f m = Tip
```

``` ucm
scratch/main> add
```

``` unison

naiomi =
  susan: Nat -> Nat -> ()
  susan a b = ()

  pam: Map Nat Nat
  pam = Tip

  mapWithKey susan pam

```