Class parameters not properly highlighted in class definitions

In the following example, only the first parameter gets highlighted as a type variable:
```purescript
class MyClass f a b where
  method :: f (a b) -> f b -> f (a b)
```

In the following example, none of the parameters get highlighted as a type variable:
```purescript
class MyClass2 (f :: * -> *) a b where
  method2 :: f (a b) -> f b -> f (a b)
```