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

foo : Foo -> Nat
foo = cases
  Bar n -> n
  Baz n m -> n + m
```

``` ucm

  Loading changes detected in scratch.u.

  I found and typechecked these definitions in scratch.u. If you
  do an `add` or `update`, here's how your codebase would
  change:
  
    ⍟ These new definitions are ok to `add`:
    
      type Foo
      foo : Foo -> Nat

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

  ⍟ I've added these definitions:
  
    type Foo
    foo : Foo -> Nat

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

``` ucm

  Loading changes detected in scratch.u.

  I found and typechecked these definitions in scratch.u. If you
  do an `add` or `update`, here's how your codebase would
  change:
  
    ⍟ These names already exist. You can `update` them to your
      new definition:
    
      type Foo

```
``` ucm
scratch/main> update

  Okay, I'm searching the branch for code that needs to be
  updated...

  That's done. Now I'm making sure everything typechecks...

  Typechecking failed. I've updated your scratch file with the
  definitions that need fixing. Once the file is compiling, try
  `update` again.

```
``` unison:added-by-ucm scratch.u
type Foo = Bar Nat

-- The definitions below no longer typecheck with the changes above.
-- Please fix the errors and try `update` again.

foo : Foo -> Nat
foo = cases
  Bar n   -> n
  Baz n m -> n Nat.+ m

```