The following are my experience and guesses, nothing
scientific/official/thoroughly tested:

> 1. can I assume that this is always going to work if u is 'a.'a   ?


Well, there is no type 'a.'a. You can have:
type u = { everything: 'a . 'a }
but this presupposes that values of type u are blocks (heap-allocated).
Therefore, if you cast a boolean (true) to type u, and then try to access
the everything field of the "new" value, you will get a segfault.

3. assuming the answer to 1. is No, is there a type u or a simple
> manipulation which should work for any type t ? Or perhaps just for
> polymorphic variants ?
>

type u = int
this will work for any type. You can even do pointer manipulation with it
(adding and subtracting even numbers of bytes).

Sorry everybody.

 - Tom