Canonical type nodes, or, comptypes considered harmful

[Richard Kenner]

> Like when int and long have the same range on a platform?
> The answer is they are different, even when they imply the same object
> representation.
> 
> The notion of unified type nodes is closer to syntax than semantics.

I'm more than a little confused, then, as to what we are talking about
canonicalizing.  We already have only one pointer to each type, for example.