Function-name completion in haskell-indentation-mode

In `haskell-indent`, it also completes the function name.

Suppose following situation:

``` haskell
fib :: Int -> Int
fib 0 = 1
-- ^ cursor here
```

When I hit `C-j` and `TAB` twice, `haskell-indent` completes the function name:

``` haskell
fib :: Int -> Int
fib 0 = 1
fib
```

But with `haskell-indentation`, function name is not completed.