isinstance + generator results in unexpected error

This code doesn't generate errors:

class A:
    y = False
a = None # type: object
(a.y for a in [A()])

However, this generates (just added isinstance):

class A:
    y = False
a = None # type: object
if isinstance(a, int): pass   # only difference
(a.y for a in [A()])

Output is like this:

program.py:7: error: "object" has no attribute "y"

The latter program shouldn't generate any error. There seems to be some weird interaction between isinstance and generator scoping.

Ah, the type in the conditional type binder probably gets propagated to the generator even though that variable there is in a different scope.

The second example works fine at least in 0.510, so Im closing this.

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