```coffeescript
# Utility functions ---------------------------------------

extend = (dest, src) ->
  dest[name] = src[name] for name in src when src[name] and !dest[name]
  dest
```

Fix bug (with my understanding of CoffeeScript)
user
```coffeescript
# Utility functions ---------------------------------------

extend = (dest, src) ->
  dest[key] = value for key, value of src when !dest[key]
  dest
```
assistant