parse error on constrained record gadt

stylish-haskell fails on the following:
```
{-# LANGUAGE GADTs #-}

data Foo a where
Foo :: (Eq a) => {
fooBar :: [a],
fooBaz :: Int
} -> Foo a

main = putStrLn "foo"
```
with this error:
```Language.Haskell.Stylish.Parse.parseModule: could not parse fail.hs: ParseFailed (SrcLoc ".hs" 4 22) "Parse error: {"```

It works if I remove the `(Eq a)` constraint. Ghc is able to compile this file properly, so I assume it's a stylish-haskell error.