I read it again (I did a year ago, but reviewed it now).  I hadn't been thinking that the *mechanism* of a new None-coalescing operator would actually be catching an exception.  It could (and should) work differently if it becomes syntax.  

What I was getting at with "essentially" was that it would *do the same thing* that an AttributeError does.  That is, if `x.foo` can't be evaluated (i.e. x doesn't have an attribute 'foo'), then access is informally "an error."  The hypothetical "x?.foo" catches that "error" and substitutes a different value.  The particular implementation under-the-hood is less important for most programmers who might use the construct (and I think documentation would actually give an informal equivalent as something similar to what I put in the NoneCoalesce class).