I think this can be fixed simpler. Currently a comprehension become asynchronous in two cases:

1. Explicitly, when it contains 'async for'. This is visible at AST level.

2. Implicitly, when any of inner expressions contains 'await'.

But asynchronous comprehensions should behave the same way as 'await'. I think that a comprehension should be made implicitly asynchronous if any of inner expressions contains explicit or implicit asynchronous comprehension. This is implemented in PR 6766.