[Python-Dev] PEP 492: No new syntax is required

[Glenn Linderman]

On 4/26/2015 4:32 PM, Paul Sokolovsky wrote:
> Then, is the only logic for proposing __aenter__ is to reinsure against
> a situation that someone starts to write async context manager, forgets
> that they write async context manager, and make an __enter__ method
> there. Then your implementation will announce that "async context
> manager lacks __aenter__", whereas "my" approach would announce
> "Async's manager __enter__ did not return awaitable value".
>
> Again, is that the distinction you're shooting for, or do I miss
> something?

Seems like the missing __aenter__ can easily be detected by the 
interpreter at compile time, but the wrong type returned would be at run 
time, or after a complex type-analysis done at compile time (unlikely to 
be practical).

So I think you've nailed the distinction... but I'm not the expert.
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