Allow non-yielding functions in `tornado.gen.coroutine`'s type hint (#2909)
Allow non-yielding functions in `tornado.gen.coroutine`'s type hint (#2909)

`@gen.coroutine` deco allows non-yielding functions, so I reflected that in the type hint.

Requires usage of `@typing.overload` due to python/mypy#9435
dongpinglai/my_tornado,mivade/tornado,mivade/tornado,lilydjwg/tornado,lilydjwg/tornado,lilydjwg/tornado,tornadoweb/tornado,dongpinglai/my_tornado,dongpinglai/my_tornado,tornadoweb/tornado,tornadoweb/tornado,dongpinglai/my_tornado,mivade/tornado,tornadoweb/tornado,lilydjwg/tornado,mivade/tornado,dongpinglai/my_tornado,dongpinglai/my_tornado,mivade/tornado