Lvalue

[Jeremy]

>The Lvalue node captures the notion that a limited subset of
>expressions can occur in two contexts -- as an expression or as the
>target of an assignment.

Ok, but is it important to express that notion in the AST typesystem?
I'm sure you have given this more though than I have, but I tend to
disagree. Maybe it is just that I loath to see AST like:

: Expr[value=Lvalue[lvalue=Attribute[value=Lvalue[lvalue=Name[id=A]], attr=b]]]

to capture the expression "A.b".

I would prefer an asdl without the "assign" type and instead:

	      | Del(expr* targets)
	      | Assign(expr* targets, expr value)
	      | AugAssign(expr target, operator op, expr value)

Yes, I know that would allow a user to manually create an semanticly
incorrect AST tree, but IMO that is what TypeErrors are good at
expressing.

Just my 2 cent.

regards,
finn