Case split is bad with lambda case


# Steps to Reproduce

```
t : Bool -> Bool
t = \case x => ?h
```

case-split on `x`

# Expected Behavior


```
t : Bool -> Bool
t = \case True => ?h_0
          False => ?h_1
```

# Observed Behavior

```
t : Bool -> Bool
t = \case False => ?h_0
t = \case True => ?h_1
```