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

```unison:hide

{{ Type doc }}
structural type Optional a =
  None
  | Some a

{{
  Multi line

  Term doc
}}
List.map : 
  (a -> b) 
  -> [a] 
  -> [b]
List.map f = cases
  (x +: xs) -> f x +: List.map f xs
  [] -> []

test> z = let
  x = "hello"
  y = "world"
  [Ok (x ++ y)]
```

```ucm
scratch/main> debug.lsp.fold-ranges
```