Regression test for https://github.com/unisonweb/unison/issues/763

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

```unison
(+-+) : Nat -> Nat -> Nat
(+-+) x y = x * y
```

```ucm
scratch/main> add
scratch/main> move.term +-+ boppitybeep
scratch/main> move.term boppitybeep +-+
```