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

```unison
unique type Foo = Bar Nat
```

```ucm
scratch/main> add
scratch/main> delete.term Foo.Bar
```

Now we've set up a situation where the original constructor missing.

```unison
unique type Foo = Bar Nat Nat
```

```ucm:error
scratch/main> view Foo
scratch/main> update
```