[py] local variable use in list comprehension not highlighted

[mtaran-google]

[x for x in blah]

Note that in python 2 (which is the main target of this mode) list/set/dict comprehensions leak the index variable(s) to the enclosing scope, but generator expressions do not. In python 3, none of them leak the index variable(s).

[marijnh]

In general, modes work front-to-back, so indeed, at the use of x, it won't have seen the declaration of x yet. I've added a kludge in attached patch to handle this specific case (the expression of a comprehension being a single variable), but I handling it generally for comprehensions where the initial expression is more complex isn't realistic with this approach. Is that acceptable?

[mtaran-google]

Let's leave this open for now. When we start showing these modes to more users, I'll pass along any bug reports.