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Issue 21947 informed the `dis` module about the `gi_code` attribute, which stores code objects for generator objects. This allows inspection of generator objects, not just functions which return them. However, asynchronous generator objects use `ag_code` and coroutine objects use `cr_code`, so dis raises a TypeError on them. I'm making a pull request to extend the generator behavior to async generators and coroutines.
Credit to Luciano Ramalho: I tripped over this at his (great) concurrency workshop at PyBay 2017 and he identified exactly what was happening and suggested a patch.

Adding Serhiy and Nick who worked on these parts of CPython.

Is this a bug fix or a new feature? Adding support of generators in issue21947 was a new feature and was not backported to older versions.

Hm--either/both? I encountered it as a bug ("dis works on my generator object and my async generator function, why does it break on my async generator object?") but strictly speaking it's a new feature (just as issue21947 was). To my mind, adding this level of indirection (finding the code object) for generators was a bit of a design decision but once it's in for generators it should be in for async generators and coroutines by analogy.

While I agree the line is blurry, extending automatic disassembly to cover new types is currently still considered a new feature in the dis module rather than a bug in the addition of those new types to the language.
Whether or not that's the *right* policy, or if we should consider tweaking it so that oversights in `dis` and `inspect` are treated as bugs in the addition of affected types, would be a question for python-dev (fortunately, the new cherry-pick based workflow means the current PR review can proceed independently of that question).

Makes sense. I'll update the PR in a bit, and if anyone is hitting this repeatedly and thinks it should be added to 3.6 they can advocate for a policy change in the maintaining-consistency-with-previous-new-features corner case.
Thanks, all!

New changeset fe2b56ab9212c1cf19c48b848fa60f7f201c366f by Nick Coghlan (syncosmic) in branch 'master':
bpo-31183: `dis` now handles coroutines & async generators (GH-3077)
https://github.com/python/cpython/commit/fe2b56ab9212c1cf19c48b848fa60f7f201c366f

Thanks for the patch!
Issue 31230 is a follow-up issue looking at whether or not we should define a general "__code__" attribute as a general purpose introspection protocol for disassembly support (amongst other generalisations of state introspection support for async operations).