The col_offset attribute for ast.AsyncFunctionDef objects points to the "def" keyword, not to the "async" keyword that actually starts the node.

Test case:

In [18]: code = 'async def f(): pass'

In [19]: tree = ast.parse(code)

In [20]: tree.body[0]
Out[20]: <_ast.AsyncFunctionDef at 0x7f5cb6a58f60>

In [21]: tree.body[0].col_offset
Out[21]: 6

The col_offset is actually correct when there is a decorator:

In [26]: code = '@decorator\nasync def f(): pass'

In [27]: tree = ast.parse(code)

In [28]: tree.body[0].col_offset
Out[28]: 0

The same issue appears with async for and async with:

In [31]: code = '@decorator\nasync def f():\n    async for x in y: pass'

In [32]: tree = ast.parse(code)

In [34]: tree.body[0].body[0]
Out[34]: <_ast.AsyncFor at 0x7f5cb6a77198>

In [35]: tree.body[0].body[0].col_offset
Out[35]: 10

Is this issue fixed? Are backports needed?

I can't reproduce the issue on master and 3.7, but can reproduce it on 3.6.