bad type function accepted as inductively sequential

```
data Baz :: * ~> * ~> * where
  Quux :: Baz Int Int

bar :: * ~> *
{bar (a `Baz` b)} = a
{bar (Baz a b)} = a

prompt> :k bar
bar :: *0 ~> *0

Branchx [0] {bar a}
 Leaf {bar (Baz b c)} --> b
 Leaf {bar (Baz d e)} --> d


But the two leaves are alpha-equivalent!
```

Original issue reported on code.google.com by `ggr...@gmail.com` on 9 Sep 2011 at 12:30
