@dselsam You have assumed that the left-hand-side (t) and
right-hand-side (s) of (t = s) and (t == s) are the last two arguments.
This is a reasonable assumption, and it is correct for eq, but it is
incorrect for heq.
The type of heq is
```
Π {α : Sort u_1}, α → Π {β : Sort u_1}, β → Prop
```
Do you recall other places where we may have made this assumption?
