Indentation can get weird after a complex type signature

Possibly related is [this issue](https://github.com/haskell/haskell-mode/issues/137).

Here's some [code that illustrates the problem](https://github.com/JeffreyBenjaminBrown/vivid/blob/64454068d98adc1a4014d0c0752fd6eeb52ab491/src/Dispatch/Join.hs). In the last function, `meta''`, there's a commented-out type signature for the subfunction called `ffxs`. (The comment says it's Intero's fault, but I was wrong about that.) If I uncomment the type signature, and then press the Tab key on the first line of the definition of `ffxs`, it bounces around indentation levels, but none of them matches the type signature's.