Incorrect indentation for 'let' inside list comprehension

Using haskell-indentation mode, I only get the indentation option marked "2" in the example below.

```
foo = [undefined |
let _ = undefined,
1 2
```

I believe 1 is the only correct indentation, because of the comma after the 'let' clause. If I go ahead and continue the code like this...

```
foo = [undefined |
let _ = undefined,
_ <- undefined,
```

...then I get the error "Illegal token: value" when I try to indent or insert a new line.