Description:

Related to #8347, (partially) blocked till 3.5 is deprecated

The goal is to;

• Convert existing name = ... # type: comments to name: type = .... (see "com2ann progress" below)
• Put type annotations on every function's parameters and return type.
• Put name: type annotations on;
  • Every class variable.
  • Every instance variable (declared in __init__() functions), unless;
    • They're constructing another instance (self.thing = Thing()) (dubious, see Use inline type hints in handlers/ and rest/ #10382 (comment))
    • They're getting assigned a non-container literal (1, b"", "", etc. but not None)
    • The assignment comes from a function/method call (self.thing = hs.get_another_thing()), given that the function signature is known and inferrable.