Closest Common Type

[Manfred Nowak]

BCS wrote:

> CCT!(E, D) // == C
> CCT!(E, C) // == C
> CCT!(E, B) // == A
> CCT!(E, A) // == A
> CCT!(E, F) // == object

To give it a name:
it's the lowest common ancestor (LCA) in the derivation tree.

-manfred